Estudio piloto: contacto padre-hijo(a) y oxitocina en varones preparados especialmente para el nacimiento / Pilot study: father-child contact and oxytocin in males with a special education for childbirth

INTRODUCCÍON: Los padres se han involucrado cada vez más en el embarazo y el nacimiento de sus hijos, pero aún se requieren intervenciones paternas que permitan reubicar al padre en su rol de corresponsabilidad en la crianza. OBJETIVO: Observar el comportamiento-actitud paterna hacia el/la hijo(a) y la cantidad de oxitocina (OT) secretada en el nacimiento, en padres preparados de un modo especial para el parto. Método: Estudio piloto de 8 meses, parte de una investigación mayor cuali-cuantitativa de dos fases. La fase cualitativa inicial desarrolló una intervención preparatoria de padres para el nacimiento, con énfasis en la vinculación padre-hijo(a). La fase cuantitativa correspondió al piloto de la intervención paterna antenatal. RESULTADOS: Los padres presenciaron activamente el momento del expulsivo y el encuentro madre-hijo(a). Posteriormente, todos optaron por el contacto físico piel-piel con su hijo(a). La OT paterna experimentó un aumento (no significativo) durante el contacto padre-hijo(a) en comparación con la OT basal (momento inmediato al nacimiento). CONCLUSIONES: Padres preparados, sensibilizados y vinculados con su hijo(a) desde el embarazo experimentarían variaciones de la cantidad de OT cuando realizan contacto piel-piel con su hijo(a) en el nacimiento. Se requiere investigación experimental con una muestra mayor de participantes para concluir de manera categórica.

INTRODUCTION: Fathers have been increasingly involved in the pregnancy and birth of their children, but paternal interventions are still required to relocate the father in his role of co-responsibility in parenting. OBJECTIVE: To observe the paternal behavior-attitude towards the child and the amount of oxytocin (OT) secreted at birth in parents prepared (in a special way) for childbirth. METHOD: Pilot study of 8 months, part of a larger qualitative-quantitative research of two phases. The initial qualitative phase developed a male preparatory intervention for the birth, with emphasis on the father-child bonding. The quantitative phase corresponded to the pilot of the antenatal paternal intervention. RESULTS: Fathers actively witnessed the moment of delivery and the mother-child attachment. Subsequently, all of them opted for physical skin-to-skin contact with their child. Paternal OT experienced a (non-significant) increase during father-child contact, compared to baseline OT (immediately after birth). CONCLUSIONS: Males prepared, sensitized and involved with their child since pregnancy would experience variations in the amount of OT when they make father-child skin-to-skin contact at childbirth. Experimental research with a larger sample of participants is required to categorically reach a conclusion.

Acciones óseas de las hormonas de la neurohipófisis / Bone actions of neuro hypophyseal hormones

La oxitocina (OXT) como la arginina-vasopresina (AVP) son dos hormonas primitivas secretadas por la hipófisis posterior. Sus receptores están mucho más ampliamente distribuidos en el organismo de lo que se pensaba originalmente, incluido el hueso. En los estudios preclínicos, la OXT ha mostrado ser anabólica para el hueso, promoviendo la osteogénesis sobre la adipogénesis y favoreciendo la actividad osteoblástica sobre la osteoclástica. Tanto los osteoblastos como los osteoclastos tienen receptores para la OXT, y los efectos de los estrógenos sobre la masa ósea en ratones está mediada por lo menos en parte por la OXT. El mecanismo preciso por el cual la activación de los receptores de oxitocina (OXTR) se traduce en un incremento de la formación ósea permanece poco claro. La AVP también podría afectar el esqueleto en forma directa. Dos de los receptores de la AVP, V1a y V2 están expresados en osteoblastos y osteoclastos. La inyección de AVP en ratones de tipo salvaje aumenta la formación osteoclastos que producen resorción y reduce los osteoblastos formadores de hueso. En forma opuesta, la exposición de precursores osteoblásticos a antagonistas de los receptores V1a o V2, incrementan la osteoblastogénesis, como también lo hace la deleción genética del receptor V1a. (AU)

Both oxytocin (OXT) and argininevasopressin (AVP) are primitive hormones secreted by the posterior pituitary gland. OXT receptors are much more widely distributed in the body than originally thought, including in bone. In preclinical studies, OXT has been shown to be anabolic for bone, promoting osteogenesis over adipogenesis and favoring osteoblastic over osteoclastic activity. Both osteoblasts and osteoclasts have receptors for OXT, and the effects of estrogen on bone mass in mice is mediated at least in part by OXT. The precise mechanism by which the activation of oxytocin receptors (OXTRs) results in an increase in bone formation remains unclear. AVP could also have direct actions on the skeleton. The two AVP receptors, V1a and V2, are expressed in osteoblasts and osteoclasts. Injection of AVP in wild-type mice increases the formation of osteoclasts increasing bone resorption, and reduces bone-forming osteoblasts. On the contrary, the exposure of osteoblastic precursors to V1a and V2 antagonists increase osteoblastogenesis, the same as the genetic deletion of the V1a receptor. (AU)

The Rostral Agranular Insular Cortex, a New Site of Oxytocin to Induce Antinociception.

The rostral agranular insular cortex (RAIC) is a relevant structure in nociception. Indeed, recruitment of GABAergic activity in RAIC promotes the disinhibition of the locus ceruleus, which in turn inhibits (by noradrenergic action) the peripheral nociceptive input at the spinal cord level. In this regard, at the cortical level, oxytocin can modulate the GABAergic transmission; consequently, an interaction modulating nociception could exist between oxytocin and GABA at RAIC. Here, we tested in male Wistar rats the effect of oxytocin microinjection into RAIC during an inflammatory (by subcutaneous peripheral injection of formalin) nociceptive input. Oxytocin microinjection produces a diminution of (1) flinches induced by formalin and (2) spontaneous firing of spinal wide dynamic range cells. The above antinociceptive effect was abolished by microinjection (at RAIC) of the following: (1) L-368899 (an oxytocin receptor [OTR] antagonist) or by (2) bicuculline (a preferent GABAA receptor blocker), suggesting a GABAergic activation induced by OTR. Since intrathecal injection of an α2A-adrenoceptor antagonist (BRL 44408) partially reversed the oxytocin effect, a descending noradrenergic antinociception is suggested. Further, injection of L-368899 per se induces a pronociceptive behavioral effect, suggesting a tonic endogenous oxytocin release during inflammatory nociceptive input. Accordingly, we found bilateral projections from the paraventricular nucleus of the hypothalamus (PVN) to RAIC. Some of the PVN-projecting cells are oxytocinergic and destinate GABAergic and OTR-expressing cells inside RAIC. Aside from the direct anatomic link between PVN and RAIC, our findings provide evidence about the role of oxytocinergic mechanisms modulating the pain process at the RAIC level.SIGNIFICANCE STATEMENT Oxytocin is a neuropeptide involved in several functions ranging from lactation to social attachment. Over the years, the role of this molecule in pain processing has emerged, showing that, at the spinal level, oxytocin blocks pain transmission. The present work suggests that oxytocin also modulates pain at the cortical insular level by favoring cortical GABAergic transmission and activating descending spinal noradrenergic mechanisms. Indeed, we show that the paraventricular hypothalamicnucleus sends direct oxytocinergic projections to the rostral agranular insular cortex on GABAergic and oxytocin receptor-expressing neurons. Together, our data support the notion that the oxytocinergic system could act as an orchestrator of pain modulation.

Oxytocin & well-being as promoters of affect regulation and homeostasis: a neuroscientific review / Ocitocina & bem-estar como promotores da regulação afetiva e da homeostase: uma revisão neurocientífica / Oxitocina y bienestar como promotores de la regulación del afecto y de la homeostasis: una revisión neurocientífica

Context: The term "Well-being" [WB] has many different meanings in scientific literature. Objectives: To search specific situations and related semantics for feelings of well-being [WB] associated to oxytocin [OT] release. Data sources: A systematic review using PRISMA guidelines in PubMed, BVS Virtual (Medline, Lilacs) and SIBI-USP Portal de Busca Integrada (1970-1999 & 2014-2018). Study selection: Reviews and clinical trials (PICOS) on OT, & WB and similar concepts in humans. Data extraction: Independent selection of articles by two reviewers; selection of articles by one reviewer, using predefined criteria. Data synthesis: 46 articles were selected out of 339, with 26 additional articles. Main data referred to social situations, sensorial stimuli, trust and psychiatric and health studies. Conclusions: The identified variables involved brain-body-mind interactions, and health/disease; translational neuroscience seems to be the best theoretical reference to investigate it.

Contexto: O termo "Bem-estar" [WB] apresenta muitos significados diferentes na literatura. Objetivos: Buscar situações específicas e semânticas relacionadas a sentimentos de bem-estar [WB] ligados à ocitocina [OT]. Fontes de dados: Revisão sistemática a partir das Referências PRISMA nas bases de dados PubMed, BVS Virtual (Medline, Lilacs) and SIBI-USP Portal de Busca Integrada (1970-1999 & 2014-2018). Seleção do estudo: revisões e ensaios clínicos (PICOS) sobre OT, & WB e sinônimos, em humanos. Extração de dados: seleção independente de artigos por dois revisores. Um revisor selecionou os textos utilizando critérios pré-definidos. Síntese dos dados: Dentre 339 artigos, 46 foram selecionados, e mais 26 posteriormente adicionados. Os principais dados obtidos referiam-se a situações sociais, estímulos sensoriais, confiança e estudos psiquiátricos e de saúde. Conclusões: As variáveis identificadas envolveram interações cérebro-corpo-mente e saúde; A neurociência translacional parece ser o melhor referencial teórico para investigá-la.

Contexto: El termo "Bienestar" [WB] abarca muchos significados diferentes en la literatura científica. Objetivos: buscar situaciones y semánticas sobre sentimientos de bienestar [WB] asociados con la produccion de oxitocina [OT]. Fuentes de datos: Revisión sistemática en PubMed, BVS Virtual (Medline, Lilacs) y SIBI-USP Portal de Busca Integrada (1970-1999; 2014-2018). Selección de estudios: revisiones y ensayos clínicos (PICOS) en OT, & WB y sinónimos, en humanos. Extracción de datos: Extracion independiente de artículos por dos revisores; selección de artículos por un revisor, utilizando criterios predefinidos. Síntesis de datos: se seleccionaron 46 artículos dentre 339, y mas 26 adicionales. Los datos principales se referían a situaciones sociales, estímulos sensoriales, confianza y estudios psiquiátricos y de salud. Conclusiones: Las variables identificadas involucraron interacciones cerebro-cuerpo-mente y salud; La neurociencia traslacional parece ser el mejor marco teórico para investigarlo.

Parindo no paraíso: parto humanizado, ocitocina e a produção corporal de uma nova maternidade / Giving birth in paradise: humanized birth, oxytocin, and the bodily production of a new maternity / Parir en el paraíso: parto humanizado, oxitocina y la producción corporal de una nueva maternidad

O Brasil é o campeão mundial no número de cesáreas, em especial no setor privado de saúde. Este número pode chegar a mais de 80% entre gestantes das classes média e alta em algumas regiões do país. Contrapondo-se a isso, o movimento do parto humanizado vem ganhando força, tendo como objetivos a denúncia da violência obstétrica e o retorno da a forma natural de parturição e cuidado com o bebê. Neste artigo, pretendemos discutir o modo como o ideário desse movimento implica na constituição de um novo sentido à maternidade a partir de uma concepção de natureza corporal e o papel da ocitocina nesse processo.(AU)

Brazil is the world champion in number of cesarean sections, especially in the private health sector. This figure can reach more than 80% among middle and upper class pregnant women in some regions of the country. Opposing this situation, the "humanized birth" movement has been gaining ground. Its objectives are the denouncement of "obstetric violence" and the return to a "natural" form of parturition and childbirth care. In this article we aim to discuss the way in which the ideas of this movement imply the constitution of a new meaning for maternity based on a conception of bodily nature, and the role played by oxytocin in this process.(AU)

Brasil es el campeón mundial en el número de cesáreas, en especial en el sector privado de la salud. este número puede llegar a más del 80% entre gestantes de clases medias y altas en algunas regiones del país. En contraposición a este estado de cosas, el movimiento del "parto humanizado" ha adquirido fuerza, teniendo como objetivos la denuncia de "violencia obstétrica" y el retorno de una forma "natural" de parto y cuidado del bebé. En este artículo pretendemos discutir la forma como el ideario de este movimiento implica en la constitución de un nuevo sentido para la maternidad a partir de una concepción de naturaleza corporal y el papel de la oxitocina en ese proceso.(AU)

Effects of intranasal oxytocin on tactile perception.

In addition to its role in childbirth labor and lactation, oxytocin is a well-known neurohormone, having several prosocial effects. Moreover, oxytocin seems to play a significant modulatory role in painful experiences, due to its participation in central and peripheral processing of nociceptive somatosensory information. Despite studies on oxytocin in pain modulation, there is a scarce literature investigating the role of oxytocin in tactile perception. Here we investigate the effects of 24 and 40 IU intranasal administration of oxytocin in the non-harmful mechanical tactile detection threshold in men. The data showed a significant increase in tactile perception in an experimental 40 IU oxytocin group. We suggest that this effect could be the basis for the oxytocin-bonding effect via touch.

Hippocampal gene expression patterns in oxytocin male knockout mice are related to impaired social interaction.

Social interaction between animals is crucial for the survival and life in groups. It is well demonstrated that oxytocin (OT) and vasopressin (AVP) play critical roles in the regulation of social behaviors in mammals, however, other neurotransmitters and hormones are involved in the brain circuitry related to these behaviors. The present study aimed to investigate the gene expression of neurotransmitter receptors in the brain of OT knockout (OTKO) male mice. In this study, we evaluated the expression levels of the OT receptor (Oxtr), AVP receptors 1a and 1b (Avpr1a; Avpr1b), dopamine receptor 2 (Drd2), and the estrogen receptors alpha and beta (Esr1; Esr2) genes in the hippocampus (HPC), olfactory bulb (OB), hypothalamus (HPT) and prefrontal cortex (PFC). AVP gene (Avp) expression was analyzed in the HPT. Gene expression results were discussed regarding to social interaction and sexual behavior findings. Additionally, we analyzed the influence of OT absence on the Avp mRNA expression levels in the HPT. RNA extraction and cDNAs synthesis followed by quantitative polymerase chain reaction were performed for gene expression determination. Results were calculated with the 2-ΔΔCt method. Our main finding was that HPC is more susceptible to gene expression changes due to the lack of OT. OTKOs exhibited decreased expression of Drd2 and Avpr1b, but increased expression of Oxtr in the HPC. In the PFC, Esr2 was increased. In the HPT, there was a reduced Avp expression in the OTKO group. No differences were detected in the OB and HPT. Despite these changes in gene expression, sexual behavior was not affected. However, OTKO showed higher social investigation and lower aggressive performance than wild-type mice. Our data highlight the importance of OT for proper gene expression of neurotransmitter receptors related to the regulation of social interaction in male mice.

Role of oxytocin in parental behaviour.

Both animal and human studies have provided conclusive evidence that oxytocin (OXT) acts in the brain (eg, medial preoptic area, ventral tegmental area, nucleus accumbens) to promote parental behaviour under different reproductive and physiological conditions. OXT appears to accelerate and strengthen the neural process that makes newborns attractive or rewarding. Furthermore, OXT reduces stress/anxiety and might improve mood and well being, resulting in indirect benefits for parents. However, OXT also plays a role in the development of species reproductive and social strategies, making some species or individuals more prone to display caring activities in nonreproductive contexts. There are important differences in the development of the OXT system and its regulation by gonadal hormones that can make individuals or species very different. Those intra- and interspecific differences in the OXT system have been associated with differences in parental behaviour. For example, differences in OXT levels in body fluids and genetic variants for the OXT and OXT receptor genes have been associated with variability in parental mood and behaviour in humans. Thus, OXT has received much attention as a potential therapeutic agent for affective, emotional and behavioural problems. Despite many preliminary studies indicating promising findings, several unknown aspects of the OXT system remain to be addressed before we can achieve a complete understanding of its function in the brain. The enormous interest that this area of study has attracted in the last decade will likely continually contribute to advancing our understanding of the role of OXT in parental behaviour and other behavioural and physiological functions.

Selective deletion of the oxytocin gene remodels the number and shape of dendritic spines in the medial amygdala of males with and without sexual experience.

Oxytocin has central actions that modulate synaptic plasticity and the occurrence of social behavior in rodents. The posterodorsal medial amygdala (MePD) composes a sexually dimorphic neural circuit for the display of male sexual behavior. Local dendritic spines are notably plastic and affected by context-dependent social stimuli. Here, we examined the effects of the selective deletion of the OT gene (OTKO) in the number and shape of Golgi-impregnated dendritic spines in the MePD of näive and sexually experienced (SexExp) male mice (n=6 each group). Compared to the control wild-type mice (WT), OTKO näive mice did not differ in the density of dendritic spines, but there was a significant and more intense reduction in the number of spines in the WT/SexExp (∼40%) than in the OTKO/SexExp (∼25%). This structural change had a spine-specific feature. That is, sexual experience induced a decrease in the number of thin (∼50%) and mushroom-like spines (∼35%) at the same time that increased (∼30%) the number of stubby/wide spines. In addition, the OTKO/SexExp animals have more thin and mushroom spines than the WT/SexExp ones (∼25% and 55%, respectively; p <0.01 in all cases). In conjunction, these novel data indicate that OT participates in the spine remodeling, synaptic refinement, and social stimuli-dependent plasticity in the MePD of male mice.

Differently shaped spines increase in the posterodorsal medial amygdala of oxytocin knockout female mice.

The posterodorsal medial amygdala (MePD) is a sexually dimorphic area in the social behavior neural network, with high concentration of oxytocin (OT) receptors. Wild type (WT) and OT knockout (OTKO) females were studied in proestrus, and Golgi-impregnated spines in the MePD were classified. Results show that the OTKO group has increased density of thin, mushroom, and stubby/wide spines when compared to the WT (p<0.01 in all cases). These data indicate that OT is an important synaptic modulator in the MePD, a finding that is likely involved with the display of the female sexual behavior.

[Oxytocin, the hormone that everyone uses and that few know]. / Oxitocina, la hormona que todos utilizan y que pocos conocen.

BACKGROUND. Oxytocin is a well known drug most commonly used in obstetrics for induction or augmentation of labor. Due to its essential role in labor, and the overall effect in the body, oxytocin must be deeply understood by all obstetricians who use it and prescribe it. There is relevant data listed about oxytocin and has reviewed the evidence in 31 full text articles of indexed journals between 1999 and 2013. In search engines like MEDLINE, MedicLatina, PUBMED, Wolters Kluwer Healt, with keywords like: oxytocin, oxytocin receptor, oxytocin vasopressin, oxytocin postpartum, oxytocin review, oxytocin labor, oxytocin release. The best evidence from the literature based on the methodology they used is included. The word oxytocin comes from the Greek words omega Chi upsilon xi, tau omicron Chi omicron chi xi, which means "swift birth". It is synthesized in the paraventricular and supraoptic nuclei of the hypotalamus is mainly released from the neurohypophysis and nerve terminals. It travels from the brain to the heart and the whole body, activating or modulating a wide range of functions and emotions. Mainly cause myometrial contractions and myoepithelial cells of the breast for milk ejection. Its adverse effects are dose-related. No one knows exactly the minumum and maximum dose of oxytocin. More research is needed about central and peripheral receptors, coupled with the use to which they currently gives to agonists and antagonists of oxytocin and its receptor. As of 2013, the documented adverse effects to date have been undervalued.

The role of oxytocin in cardiovascular regulation.

Studies of body volume expansion have indicated that lesions of the anteroventral third ventricle and median eminence block the release of atrial natriuretic peptide (ANP) into the circulation. Detailed analysis of the lesions showed that activation of oxytocin (OT)-ergic neurons is responsible for ANP release, and it has become clear that activation of neuronal circuitry elicits OT secretion into the circulation, activating atrial OT receptors and ANP release from the heart. Subsequently, we have uncovered the entire functional OT system in the rat and the human heart. An abundance of OT has been observed in the early development of the fetal heart, and the capacity of OT to generate cardiomyocytes (CMs) has been demonstrated in various types of stem cells. OT treatment of mesenchymal stem cells stimulates paracrine factors beneficial for cardioprotection. Cardiovascular actions of OT include: i) lowering blood pressure, ii) negative inotropic and chronotropic effects, iii) parasympathetic neuromodulation, iv) vasodilatation, v) anti-inflammatory activity, vi) antioxidant activity, and vii) metabolic effects. OT actions are mediated by nitric oxide and ANP. The beneficial actions of OT may include the increase in glucose uptake by CMs and stem cells, reduction in CM hypertrophy, oxidative stress, and mitochondrial protection of several cell types. In experimentally induced myocardial infarction in rats, continuous in vivo OT delivery improves cardiac healing and cardiac work, reduces inflammation, and stimulates angiogenesis. Because OT plays anti-inflammatory and cardioprotective roles and improves vascular and metabolic functions, it demonstrates potential for therapeutic use in various pathologic conditions.

The role of oxytocin in cardiovascular regulation

Studies of body volume expansion have indicated that lesions of the anteroventral third ventricle and median eminence block the release of atrial natriuretic peptide (ANP) into the circulation. Detailed analysis of the lesions showed that activation of oxytocin (OT)-ergic neurons is responsible for ANP release, and it has become clear that activation of neuronal circuitry elicits OT secretion into the circulation, activating atrial OT receptors and ANP release from the heart. Subsequently, we have uncovered the entire functional OT system in the rat and the human heart. An abundance of OT has been observed in the early development of the fetal heart, and the capacity of OT to generate cardiomyocytes (CMs) has been demonstrated in various types of stem cells. OT treatment of mesenchymal stem cells stimulates paracrine factors beneficial for cardioprotection. Cardiovascular actions of OT include: i) lowering blood pressure, ii) negative inotropic and chronotropic effects, iii) parasympathetic neuromodulation, iv) vasodilatation, v) anti-inflammatory activity, vi) antioxidant activity, and vii) metabolic effects. OT actions are mediated by nitric oxide and ANP. The beneficial actions of OT may include the increase in glucose uptake by CMs and stem cells, reduction in CM hypertrophy, oxidative stress, and mitochondrial protection of several cell types. In experimentally induced myocardial infarction in rats, continuous in vivo OT delivery improves cardiac healing and cardiac work, reduces inflammation, and stimulates angiogenesis. Because OT plays anti-inflammatory and cardioprotective roles and improves vascular and metabolic functions, it demonstrates potential for therapeutic use in various pathologic conditions.

Sexual behavior and dendritic spine density of posterodorsal medial amygdala neurons in oxytocin knockout female mice.

Central oxytocin (OT) and arginine-vasopressin (AVP) have been shown to play an important role in sexual behavior and neuroendocrine secretion in rodents. The results of exogenous OT administration on sexual behaviors in male and female mice are controversial. This study aimed to analyze the role of OT in sexual behavior, the number of oocytes and the density of dendritic spines in the posterodorsal medial amygdala (MePD) of female mice with selective deletion of the OT gene (OTKO). Female C57BL/6 mice were genotyped and divided into control (WT) and OTKO groups (n=11 each). All experiments were performed in the proestrus phase. Compared to WT data, our results showed that the OTKO group had a significant increase in the latency for the display of lordosis behavior (490.8 ± 113.8 and 841.9 ± 53.9, respectively) and a decrease in both the frequency (6.3 ± 2.4 and 0.5 ± 0.4) and duration (49.3 ± 19.9 and 7.2 ± 7.1) of lordosis and a reduction in the number of oocytes (12.2 ± 0.8 and 9.9 ± 0.6). However, the OTKO group showed a higher density of proximal dendritic spines in the MePD compared to the WT group (2.4 ± 0.1 and 1.9 ± 0.1 spines/dendritic µm, respectively). No significant difference was observed in the plasma levels of AVP between the groups (OTKO: 617.1 ± 96.0 and WT: 583.3 ± 112.0 pg/mL). Our data suggest that OT plays a crucial role in the sexual behavior display, number of released oocytes and density of dendritic spines in the MePD of female mice. The AVP plasma concentration was not affected in the OTKO animals.

Oxytocin projections to the nucleus of the solitary tract contribute to the increased meal-related satiety responses in primary adrenal insufficiency.

Anorexia is a common clinical manifestation of primary adrenal gland failure. Adrenalectomy (ADX)-induced hypophagia is reversed by oxytocin (OT) receptor antagonist and is associated with increased activation of satiety-related responses in the nucleus of the solitary tract (NTS). This study evaluated OT projections from the paraventricular nucleus of the hypothalamus (PVN) to the NTS after ADX and the effect of pretreatment with intracerebroventricular injection of an OT receptor antagonist ([d(CH2)5,Tyr(Me)(2),Orn(8)]-vasotocin; OVT) on the activation of NTS neurons induced by feeding in adrenalectomized rats. Adrenalectomized animals showed higher OT labelling in the NTS than the sham and the ADX with corticosterone replacement (ADX + B) groups. Adrenalectomized animals exhibited co-localization of the anterograde tracer Phaseolus vulgaris leucoagglutinin and OT in axons in the NTS as well as OT fibres apposing NTS neurons activated by refeeding. After vehicle pretreatment, compared with fasting, refeeding increased the numbers of Fos- and Fos + TH-immunoreactive neurons in the NTS in sham, ADX and ADX + B groups, with a higher number of these immunolabelled neurons in adrenalectomized animals. Compared with fasting conditions, refeeding also increased the activation of NTS neurons in OVT-pretreated sham, ADX and ADX + B groups, but there was no difference among the three experimental groups. These data demonstrate that OT is upregulated in projections to the NTS following ADX and that OT receptor antagonist reverses the greater activation of NTS neurons induced by feeding after ADX. The data indicate that OT pathways to the NTS contribute to higher satiety-related responses and, thus, to reduce meal size in primary adrenal insufficiency.

Role of oxytocin in energy metabolism.

The basic mechanisms that lead obesity are not fully understood; however, several peptides undoubtedly play a role in regulating body weight. Obesity, a highly complex metabolic disorder, involves central mechanisms that control food intake and energy expenditure. Previous studies have shown that central or peripheral oxytocin administration induces anorexia. Recently, in an apparent discrepancy, rodents that were deficient in oxytocin or the oxytocin receptor were shown to develop late-onset obesity without changing their total food intake, which indicates the physiological importance of oxytocin to body metabolism. Oxytocin is synthesized not only within magnocellular and parvocellular neurons but also in several organs, including the ovary, uterus, placenta, testis, thymus, kidney, heart, blood vessels, and skin. The presence of oxytocin receptors in neurons, the myometrium and myoepithelial cells is well recognized; however, this receptor has also been identified in other tissues, including the pancreas and adipose tissue. The oxytocin receptor is a typical class I G protein-coupled receptor that is primarily linked to phospholipase C-ß via Gq proteins but can also be coupled to other G proteins, leading to different functional effects. In this review, we summarize the present knowledge of the effects of oxytocin on controlling energy metabolism, focusing primarily on the role of oxytocin on appetite regulation, thermoregulation, and metabolic homeostasis.

Oxytocin modulates social interaction but is not essential for sexual behavior in male mice.

Recently, several studies have shown different conclusions regarding the effect of oxytocin (OT) on the social behaviors of male mice. Most of these studies used exogenous OT, but currently, investigations of the neural bases of social behavior are increasingly employing gene inactivation. This study aimed to analyze the role of OT in the modulation of social behaviors (i.e., sexual and social interaction behaviors) in male mice with selective deletions of the OT gene (OTKO) and the influence of this deletion in basal vasopressin (AVP) plasma concentrations. Our results showed that in the social interaction test, OTKO mice exhibited lower levels of social behaviors and higher levels of non-social behaviors compared to the wild type (WT) group. Additionally, the OTKO group showed a decrease in the number of agonistic behaviors delivered, and consequently, their dominance score was lower than that of the WT group. In the ethological analysis, the OTKO group had a lower aggressive performance and increased social investigation than the WT group. No significant differences were observed in the sexual behavior between groups. Finally, we found lower AVP plasma concentrations in the OTKO compared with the WT group. In conclusion, our data suggest that OT modulates social investigation behavior and the aggressiveness of male mice. The decrease in AVP concentrations in the OTKO group allows us to infer that AVP is physiologically relevant to these behavioral modulations. However, sexual behaviors do not seem to be affected by the lack of OT or by a decrease in the AVP concentration.

Oxytocin in the central amygdaloid nucleus modulates the neuroendocrine responses induced by hypertonic volume expansion in the rat.

The present study investigated the involvement of the oxytocinergic neurones that project into the central amygdala (CeA) in the control of electrolyte excretion and hormone secretion in unanaesthetised rats subjected to acute hypertonic blood volume expansion (BVE; 0.3 M NaCl, 2 ml/100 g of body weight over 1 min). Oxytocin and vasopressin mRNA expression in the paraventricular (Pa) and supraoptic nucleus (SON) of the hypothalamus were also determined using the real time-polymerase chain reaction and in situ hybridisation. Male Wistar rats with unilaterally implanted stainless steel cannulas in the CeA were used. Oxytocin (1 µg/0.2 µl), vasotocin, an oxytocin antagonist (1 µg/0.2 µl) or vehicle was injected into the CeA 20 min before the BVE. In rats treated with vehicle in the CeA, hypertonic BVE increased urinary volume, sodium excretion, plasma oxytocin (OT), vasopressin (AVP) and atrial natriuretic peptide (ANP) levels and also increased the expression of OT and AVP mRNA in the Pa and SON. In rats pre-treated with OT in the CeA, previously to the hypertonic BVE, there were further significant increases in plasma AVP, OT and ANP levels, urinary sodium and urine output, as well as in gene expression (AVP and OT mRNA) in the Pa and SON compared to BVE alone. Vasotocin reduced sodium, urine output and ANP levels, although no changes were observed in plasma AVP and OT levels or in the expression of the AVP and OT genes in both hypothalamic nuclei. The results of the present study suggest that oxytocin in the CeA exerts a facilitatory role in the maintenance of hydroelectrolyte balance in response to changes in extracellular volume and osmolality.

Oxitocina, vasopresina y conducta social: hipótesis neuropéptida para el trastorno autista / Oxytocin, vasopressin and social behavior: neuropeptide hypothesis

Introducción: El Trastorno Autista es una patología de inicio temprano que evoluciona hacia la cronicidad y se caracteriza principalmente por un desarrollo marcadamente anormal o deficiente de la interacción y comunicación social. Es más frecuente en hombres y si bien se presume que es de origen multifactorial, se plantea que puede ser explicado, al menos en parte, por una alteración en la neurobiología que da sustento a las conductas sociales normales. La Oxitocina y la Vasopresina han sido ampliamente relacionadas con las conductas sociales tanto en animales como en humanos, específicamente han sido relacionadas con las conductas de apego, de filiación y con el Trastorno Autista. Objetivos: Entregar un marco teórico que contribuya a organizar el amplio conocimiento que existe sobre la fisiopatología del Trastorno Autista y que entregue luces tanto para la investigación como para la clínica. Método: Se realiza una revisión bibliográfica sobre el rol que juegan la Oxitocina y la Vasopresina en las conductas sociales sanas y anormales tanto en animales como en humanos centrándose la discusión en la relación que tienen estos neuropéptidos con el Trastorno Autista. Conclusiones: Si bien se presume que la fisiopatología del Trastorno Autista es de origen multifactorial, se logra organizar un marco teórico para la comprensión de la fisiopatología del trastorno desde una hipótesis neuropéptida, lo cual tiene implicancias tanto para la investigación como para la clínica.

Introduction: Autistic disorder is an early onset disease that evolves into chronicity, characterized by the presence of markedly abnormal or deficient development of social interaction and communication. It is more common in men and although presumed to be of multifactorial origin, it is proposed that it can be explained, at least in part, by alterations in the neurobiology which gives supports to normal social behavior. Oxytocin and vasopressin have been widely associated with social behavior in animals and humans, specifically with attachment behaviors, affiliation and Autistic Disorder. Objectives: To provide a theoretical framework in order to help organize the extensive knowledge that exists about the pathophysiology of autistic disorder and to deliver light for both research and clinic. Methods: We performed a systematic review of the role played by oxytocin and vasopressin in healthy and abnormal social behavior in both animals and humans and focused the discussion on the relationship that have these neuropeptides with Autistic Disorder. Conclusions: Understanding the pathophysiology of the Autistic Disorder from a neuropeptide hypothesis, provides a theorethical framework which has implications for both research and clinic.

Hormones and sexual reward.

There are different physiological processes that influence behavior. One of this processes that produces approach behavior to a stimuli that induces a positive affective (PA) state, commonly known as reward, plays an important role in modulating behavior. There is an extensive literature in which the rewarding effects of drugs have been investigated. Less research has been devoted to the study of naturally occurring behaviors that produce a PA or reward state. Hormones modulate different behaviors, including sex. However, little attention has been devoted to study the possible role of hormones in reward states. One of the methods most frequently used to study reward or PA states is the conditioned place preference (CPP) paradigm. Hopefully this review will encourage researchers to directly address the effects of hormones on reward, research that is much needed.