Neuropeptidergic Control of Feeding: Focus on the Galanin Family of Peptides.

Obesity/overweight are important health problems due to metabolic complications. Dysregulation of peptides exerting orexigenic/anorexigenic effects must be investigated in-depth to understand the mechanisms involved in feeding behaviour. One of the most important and studied orexigenic peptides is galanin (GAL). The aim of this review is to update the mechanisms of action and physiological roles played by the GAL family of peptides (GAL, GAL-like peptide, GAL message-associated peptide, alarin) in the control of food intake and to review the involvement of these peptides in metabolic diseases and food intake disorders in experimental animal models and humans. The interaction between GAL and NPY in feeding and energy metabolism, the relationships between GAL and other substances involved in food intake mechanisms, the potential pharmacological strategies to treat food intake disorders and obesity and the possible clinical applications will be mentioned and discussed. Some research lines are suggested to be developed in the future, such as studies focused on GAL receptor/neuropeptide Y Y1 receptor interactions in hypothalamic and extra-hypothalamic nuclei and sexual differences regarding the expression of GAL in feeding behaviour. It is also important to study the possible GAL resistance in obese individuals to better understand the molecular mechanisms by which GAL regulates insulin/glucose metabolism. GAL does not exert a pivotal role in weight regulation and food intake, but this role is crucial in fat intake and also exerts an important action by regulating the activity of other key compounds under conditions of stress/altered diet.

Neuroanatomical relationship between the cholinergic and tachykininergic systems in the adult human brainstem: An immunohistochemical study.

The cholinergic system plays an important role in brain homeostasis and interacts with the neuropeptidergic systems, and the functional relationships between both systems are well known. However, in the brainstem the possible physiological interactions between neurokinins and acetylcholine are unknown, although both substances have been detected in the same brainstem nuclei and have been implicated in similar functions controlled from brainstem regions such as some cranial motor nuclei. The aim of this work is to determine whether these possible physiological interactions might have a neuroanatomical basis by means of the double immunohistochemical detection of neurokinins (NK) and the enzyme choline acetyl-transferase (ChAT) in the human brainstem. No double-labelled structures were detected, although both NK and ChAT were observed in cell bodies and fibers of the same brainstem nuclei. The distribution of immunoreactive fibers is widespread, and NK and ChAT were observed in several motor cranial nerves as well as in the substantia nigra. The results obtained in the present work provide a neuroanatomical basis for possible physiological interactions between NK and ChAT that may be carried out by volume-transmission mechanisms. These interactions might participate in motor regulation or in limbic pathways as well as influence on other neurotransmitter systems such as the dopaminergic system.

The involvement of the substance P/neurokinin 1 receptor system in viral infection: focus on the gp120 fusion protein and homologous dipeptide domains.

The human immunodeficiency virus (HIV) envelope, via a key extracellular amino acid sequence, may simulate the functionality of native undecapeptide substance P (SP) acting through the host's neurokinin 1 (SP preferring) receptor (NK-1R). Human monocytes and macrophages express both NK-1Rs and SP. In HIV/AIDS the NK-1R may function as a chemokine-like G-protein coupled co-receptor that: 1) fuses to the outer envelope of HIV; 2) enables intracellular entry of the envelope-capsid-NK-1R complex; 3) co-opts immune defence via its physiological interaction with the SP-like envelope; 4) may contribute to resistance of CD4/chemokine entry inhibitor type drugs; 5) relaxes the blood-brain barrier to support entry of the HIV into the central nervous system, and 6) mediates most of the common clinical sequelae of HIV/AIDS (encephalopathy and AIDS dementia complex). The data support the idea that NK-1R antagonists could be useful to treat HIV/AIDS. Keywords: human immunodeficiency virus; NK-1 receptor; NK-1 receptor antagonist; aprepitant; fusion protein; virus.

Distribution of somatostatin-28 (1-12), calcitonin gene-related peptide, and substance P in the squirrel monkey brainstem: an immunocytochemical study.

Using an immunocytochemical technique, we have studied the distribution of fibers and cell bodies containing somatostatin-28 (1-12) [SOM-28 (1-12)], calcitonin gene-related peptide (CGRP), and substance P (SP) in the brainstem of Saimiri sciureus. The distribution of the peptidergic cell bodies was very restricted: perikarya containing SOM-28 (1-12) were only observed in the substantia grisea centralis, while no immunoreactive cell bodies containing CGRP or SP were visualized. Fibers containing SOM-28 (1-12), CGRP, or SP were widely distributed in the brainstem: immunoreactive fibers containing SOM-28 (1-12) showed the most widespread distribution and were the most abundant. The distribution of SOM-28 (1-12)-, CGRP- or SP-immunoreactive fibers was very similar. Colocalization of immunoreactive fibers containing SOM-28 (1-12), CGRP or SP was observed in many brainstem nuclei. A neuroanatomical relationship between CGRP- and SP-immunoreactive fibers was observed, although this relationship was less marked for SOM-28 (1-12) and SP and lower still for SOM-28 (1-12) and CGRP. The widespread distribution of the peptidergic fibers suggests that the studied neuropeptides are involved in many physiological actions.

Overexpression of kynurenic acid in stroke: An endogenous neuroprotector?

It is known that kynurenic acid (KYNA) exerts a neuroprotective effect against the neuronal loss induced by ischemia; acting as a scavenger, and exerting antioxidant action. In order to study the distribution of KYNA, a highly specific monoclonal antibody directed against KYNA was developed. This distribution was studied in control rats and in animals in which a middle cerebral artery occlusion (stroke model) was induced. By double immunohistochemistry, astrocytes containing KYNA and GFAP were exclusively found in the ipsilateral cerebral cortex and/or striatum, at 2, 5 and 21days after the induction of stroke. In control animals and in the contralateral side of the stroke animals, no immunoreactivity for KYNA was found. Under pathological conditions, the presence of KYNA is reported for the first time in the mammalian brain from early phases of stroke. The distribution of KYNA matches perfectly with the infarcted regions suggesting that, in stroke, this overexpressed molecule could be involved in neuroprotective/scavenger/antioxidant mechanisms.

NO-tryptophan: a new small molecule located in the rat brain.

A highly specific monoclonal antibody directed against nitric oxide-tryptophan (NO-W) with good affinity (10-9 M) and specificity was developed. In the rat brain, using an indirect immunoperoxidase technique, cell bodies containing NO-W were exclusively found in the intermediate and dorsal parts of the lateral septal nucleus. No immunoreactive fibres were found in the rat brain. This work reports the first visualization and the morphological characteristics of cell bodies containing NO-W in the mammalian brain. The restricted distribution of NO-W in the rat brain suggests that this molecule could be involved in specific physiological mechanisms.

Mapping of methionine-enkephalin-arg6-gly7-leu8 in the human diencephalon.

Using an immunohistochemical technique, we mapped the immunoreactive structures containing methionine-enkephalin-Arg6-Gly7-Leu8 (Met-8) (a marker for the pro-enkephalin system) in the human diencephalon. Compared with previous studies, we observed a more widespread distribution of Met-8 in the human diencephalon. Met-8-immunoreactive cell bodies and fibers exhibited a more widespread distribution in the hypothalamus than in the thalamus. We observed six populations of Met-8-immunoreactive cell bodies. These perikarya were observed in the paratenial thalamic nucleus, ventromedial and dorsomedial hypothalamic nuclei, lateral hypothalamic area, pallidohypothalamic nucleus and in the paraventricular hypothalamic nucleus (posterior part). In the thalamus, Met-8-immunoreactive fibers were primarily observed in the midline region, whereas in the hypothalamus, these fibers were widely distributed. In general, a moderate/low density of Met-8-immunoreactive fibers was observed in the diencephalic nuclei. A moderate density was observed in the paraventricular thalamic nucleus, reuniens thalamic nucleus, lateral and medial geniculate nuclei, dorsomedial hypothalamic nucleus, paraventricular hypothalamic nucleus (posterior part) and ventromedial hypothalamic nucleus. The present study is the first to demonstrate the presence of clusters of Met-8-immunoreactive cell bodies in the human thalamus and hypothalamus, the distribution of fibers containing neuropeptides in the hypothalamus and the presence of these fibers in several thalamic nuclei. This neuroanatomical study will serve to elucidate the physiological roles of Met-8 in future studies of the human diencephalon.

3-hydroxi-anthranilic acid is early expressed in stroke.

Using an immunohistochemical technique, we have studied the distribution of 3-OH-anthranilic acid (3-HAA) in the rat brain. Our study was carried out in control animals and in rats in which a stroke model (single transient middle cerebral artery occlusion) was performed. A monoclonal antibody directed against 3-HAA was also developed. 3-HAA was exclusively observed in the infarcted regions (ipsilateral striatum/cerebral cortex), 2, 5 and 21 days after the induction of stroke. In control rats and in the contralateral side of the stroke animals, no immunoreactivity for 3-HAA was visualized. Under pathological conditions (from early phases of stroke), we reported for the first time the presence of 3-HAA in the mammalian brain. By double immunohistochemistry, the coexistence of 3-HAA and GFAP was observed in astrocytes. The distribution of 3-HAA matched perfectly with the infarcted regions. Our findings suggest that, in stroke, 3-HAA could be involved in the tissue damage observed in the infarcted regions, since it is well known that 3-HAA exerts cytotoxic effects.

Distribution of Neurotensin and Somatostatin-28 (1-12) in the Minipig Brainstem.

Using an indirect immunoperoxidase technique, an in depth study has been carried out for the first time on the distribution of fibres and cell bodies containing neurotensin and somatostatin-28 (1-12) (SOM) in the minipig brainstem. The animals used were not treated with colchicine. The distribution of neurotensin- and SOM-immunoreactive fibres was seen to be quite similar and was moderate in the minipig brainstem: a close anatomical relationship between both neuropeptides was observed. The distribution of cell bodies containing neurotensin or SOM was quite different and restricted. Cell bodies containing neurotensin were found in four brainstem nuclei: nucleus centralis raphae, nucleus dorsalis raphae, in the pars centralis of the nucleus tractus spinalis nervi trigemini and in the nucleus ventralis raphae. Cell bodies containing SOM were found in six nuclei/regions of the brainstem: nucleus ambiguus, nucleus dorsalis motorius nervi vagus, formatio reticularis, nucleus parabrachialis medialis, nucleus reticularis lateralis and nucleus ventralis raphae. According to the observed anatomical distribution of the immunoreactive structures containing neurotensin or SOM, the peptides could be involved in sleep-waking, nociceptive, gustatory, motor, respiratory and autonomic mechanisms.

Developmental study of vitamin C distribution in children's brainstems by immunohistochemistry.

Vitamin C (Vit C) is an important antioxidant, exerts powerful neuroprotective brain effects and plays a role in neuronal development and maturation. Vit C is present in brain tissue at higher concentrations than in other organs, but its detailed distribution in brain is unknown. Immunohistochemical detection of this vitamin has been performed by using a highly specific antibody against Vit C. The aim of the present work was to analyze the distribution of Vit C in children's brainstems during postnatal development, comparing two groups of ages: younger and older than one year of life. In general, the same areas showing neurons with Vit C in young cases are also immunostained at older ages. The distribution of neurons containing Vit C was broader in the brainstems of older children, suggesting that brainstem neurons maintain or even increase their ability to retain Vit C along the life span. Immunohistochemical labeling revealed only cell bodies containing this vitamin, and no immunoreactive fibers were observed. The distribution pattern of Vit C in children's brainstems suggests a possible role of Vit C in brain homeostatic regulation. In addition, the constant presence of Vit C in neurons of locus coeruleus supports the important role of Vit C in noradrenaline synthesis, which seemed to be maintained along postnatal development.

The antiproliferative action of [D-Arg(1), D-Phe(5), D-Trp(7,9), LEU(11)] substance P analogue antagonist against small-cell- and non-small-cell lung cancer cells could be due to the pharmacological profile of its tachykinin receptor antagonist.

It is known that in human lung cancer samples, both small-cell lung cancer (SCLC) and non-small-cell lung cancer (NSCLC) cells express the neurokinin-1 (NK-1) receptor; that after binding to the NK-1 receptor the peptide substance P (SP) elicits tumour cell proliferation and an antiapoptotic effect. By contrast, it has been demonstrated that non-peptide NK-1 receptor antagonists, after binding to the NK-1 receptor and hence by blocking the SP action in SCLC/NSCLC, exert an antiproliferative action (inhibit lung cancer cell proliferation and induce the death of tumour cells by apoptosis). It is also known that SP peptide NK-1 receptor antagonists also called SP analogue antagonists (broad-spectrum GPCR antagonists, broad-spectrum neuropeptide antagonists or synthetic analogues of SP), also exert antiproliferative actions against SCLC/NSCLC. However, the underlying mechanisms involved in this antiproliferative action remain unknown. By using competition assays with SP, here we demonstrate that the antiproliferative action exerted by the [D-Arg(1), D-Phe(5), D-Trp(7,9), Leu(11)] SP analogue on human H-69 SCLC and COR-L23 NSCLC cell lines, occurs at least through the NK-1 receptor.

Immunohistochemical mapping of pro-opiomelanocortin- and pro-dynorphin-derived peptides in the alpaca (Lama pacos) diencephalon.

Using an indirect immunoperoxidase technique, we studied the distribution of cell bodies and fibres containing non-opioid peptides (adrenocorticotropin hormone (ACTH), alpha-melanocyte-stimulating hormone) and opioid peptides (beta-endorphin (1-27), alpha-neo-endorphin, leucine-enkephalin) in the alpaca diencephalon. No immunoreactive cell bodies containing ACTH were found. Perikarya containing the other four peptides were observed exclusively in the hypothalamus and their distribution was restricted. Perikarya containing alpha-melanocyte-stimulating hormone or alpha-neo-endorphin showed a more widespread distribution than those containing leucine-enkephalin or beta-endorphin (1-27). Cell bodies containing pro-opiomelanocortin-derived peptides were observed in the arcuate nucleus, anterior and lateral hypothalamic areas and in the ventromedial and supraoptic hypothalamic nuclei, whereas perikarya containing alpha-neo-endorphin (a pro-dynorphin-derived peptide) were found in the arcuate nucleus, dorsal and lateral hypothalamic areas, and in the paraventricular, ventromedial and supraoptic hypothalamic nuclei. Immunoreactive cell bodies containing leucine-enkephalin were found in the lateral hypothalamic area and in the paraventricular hypothalamic nucleus. Immunoreactive fibres expressing pro-opiomelanocortin-derived peptides were more numerous than those expressing pro-dynorphin-derived peptides. A close anatomical relationship was observed: in all the diencephalic nuclei in which beta-endorphin (1-27)-immunoreactive fibres were found, fibres containing alpha-melanocyte-stimulating hormone or alpha-neo-endorphin were also observed. Fibres containing beta-endorphin (1-27), alpha-melanocyte-stimulating hormone or alpha-neo-endorphin were widely distributed throughout the diencephalon, but fibres containing ACTH or leucine-enkephalin showed a moderate distribution. The distribution of the five peptides studied here is also compared with that reported previously in other mammalian species. The widespread distribution observed indicates that both the pro-dynorphin and the pro-opiomelanocortin systems are involved in multiple physiological actions (e.g., food intake, thermoregulation, neuroendocrine and reproductive mechanisms) in the alpaca diencephalon.

Developmental study of the distribution of hypoxia-induced factor-1 alpha and microtubule-associated protein 2 in children's brainstem: comparison between controls and cases with signs of perinatal hypoxia.

Perinatal asphyxia and hypoxia are common causes of morbidity in neonates. Prenatal birth associated with hypoxemia often results in several disorders because of the lack of oxygen in the brain. Survival rates from perinatal hypoxia have improved, but appropriate treatments for recovery are still limited, with great impact on patients, their families, society in general and health systems. The aim of this work is to contribute to a better understanding of the cellular mechanisms underlying the brainstem responses to hypoxia. For this purpose, distributions of two proteins, hypoxia-inducible factor-1 alpha (HIF-1α) and microtubule-associated protein 2 (MAP-2) were analyzed in brainstems of 11 children, four of them showing neuropathological evidence of brain hypoxia. They were included in control or hypoxic groups, and then in several subgroups according to their age. Immunohistochemical labeling for these proteins revealed only cell bodies containing HIF-1α, and both cell bodies and fibers positive for MAP-2 in the children's brainstems. The distribution of HIF-1α was more restricted than that of MAP-2, and it can be suggested that the expression of HIF-1α increased with age. The distribution pattern of MAP-2 in the medulla oblongata could be more due to age-related changes than to a response to hypoxic damage, whereas in the pons several regions, such as the nucleus ambiguus or the solitary nucleus, showed different immunolabeling patterns in controls and hypoxic cases. The distribution patterns of these two proteins suggest that some brainstem regions, such as the reticular formation or the central gray, could be less affected by conditions of hypoxia.

Mapping of neurotensin in the alpaca (Lama pacos) brainstem.

We studied the distribution of cell bodies and fibres containing neurotensin (NT) in the brainstem of the alpaca using an indirect immunoperoxidase technique. Immunoreactive fibres were widely distributed throughout the brainstem, whereas the distribution of cell bodies was less widespread. Immunoreactive perikarya were only found in the mesencephalic and bulbar reticular formation, periaqueductal grey, nucleus of the solitary tract, laminar spinal trigeminal nucleus and in the inferior colliculus. A high density of fibres containing NT was found in the dorsal nucleus of the raphe, marginal nucleus of the brachium conjunctivum, locus coeruleus, inferior colliculus, inter-peduncular nucleus, substantia nigra, periaqueductal grey, reticular formation of the mesencephalon, pons and medulla oblongata, nucleus of the solitary tract, laminar spinal trigeminal nucleus, hypoglossal nucleus, inferior central nucleus and in the tegmental reticular nucleus. The widespread distribution indicates that NT might be involved in multiple physiological actions in the alpaca brainstem; this must be investigated in the future as alpacas lives from 0 m above sea level to altitudes of up 5000 m and hence the involvement of this neuropeptide in special and unique regulatory physiological mechanisms could be suggested.

Classical neurotransmitters and neuropeptides involved in major depression in a multi-neurotransmitter system: a focus on antidepressant drugs.

We summarize the alterations of classical neurotransmitters and neuropeptides and the corresponding subreceptors involved in major depression. Neuronal circuits in the brainstem, hippocampus and hypothalamus are developed, since they can be used to derive a multimodal pharmacotherapy. In this sense, serotonin hypoactivity could occur through a strong presynaptic inhibition of glutaminergic neurons via the subtype 5 of metabotropic glutaminergic receptors, and noradrenaline hypoactivity could be due to an enhanced presynaptic inhibition of GABAergic neurons via GABAB receptors. In the hippocampus, dopamine hypoactivity leads to a decreased positive effect. In clinical trials, the antidepressant effect of drugs interfering with the mentioned subreceptors, for example the triple reuptake inhibitor amitifadine, is being investigated. Moreover, the alterations of neuropeptides, such as corticotropin-releasing hormone, neuropeptide Y and galanin are pointed out. The additional antidepressant effect of analogs, agonists and antagonists of the mentioned neuropeptides should be examined.

Mapping of tyrosine hydroxylase in the diencephalon of alpaca (Lama pacos) and co-distribution with somatostatin-28 (1-12).

Based on previous work describing the distribution of somatostatin-28 (1-12) in the male alpaca (Lama pacos) diencephalon, and owing to the well known interactions between this peptide and the catecholaminergic system, the aims of this work are (1) to describe the distribution of putative catecholaminergic cell groups in the alpaca diencephalon and (2) to study the possible morphological basis of the interactions between these substances in the diencephalon of the alpaca by using double immunohistochemistry methods. Thus, the distribution of catecholaminergic cell groups in the alpaca diencephalon agrees with that previously described in the diencephalon of other mammalian species of the same order: the A11, A12, A13, A14 and A15d cell groups have been identified; however, we have observed an additional hitherto undescribed cell group containing tyrosine hydroxylase in the medial habenula. In addition, double-labelling procedures did not reveal neurons containing tyrosine hydroxylase and somatostatin, suggesting that the hypothalamic interactions between catecholamines and somatostatin at intra-cellular level must be carried out by a somatostatin molecule other than fragment (1-12). Otherwise, the overlapping distribution patterns of these substances would suggest some interconnections between groups of chemospecific neurons. These results could be the starting point for future studies on hypothalamic functions in alpacas, for example those concerning reproductive control, since other physiological studies have suggested that this species could have different regulatory mechanisms from other mammalian species. Our results support the Manger hypothesis that the same nuclear complement of neural systems exists in the brain of species of the same order.

Mapping of CGRP in the alpaca diencephalon.

We report the distribution of immunoreactive cell bodies and fibers containing calcitonin gene-related peptide in the alpaca diencephalon. This study was carried out in alpacas that lived from birth to death at 0 m above sea level. Immunoreactive fibers were widely distributed throughout the thalamus and hypothalamus. A moderate density of these fibers was found in the zona incerta, the central medial, subparafascicular, reuniens and rhomboid thalamic nuclei, in the preoptic, anterior, lateral and dorsal hypothalamic areas, around the fornix, in the posterior, ventromedial and paraventricular hypothalamic nuclei and in the lateral mammillary nucleus. Cell bodies were only found in the hypothalamus: a high density in the paraventricular and supraoptic hypothalamic nuclei and a low density in the anterior, lateral and dorsal hypothalamic areas, around the fornix, and in the posterior and ventromedial hypothalamic nuclei. The widespread distribution of calcitonin gene-related peptide in the alpaca diencephalon suggests that it is involved in many physiological actions that must be investigated in-depth in the future, since alpacas lives from 0 m above sea level to altitudes of up to 5000 m altitude and hence the involvement of neuropeptides in special and unique regulatory physiological mechanisms could be suggested.

NK-1 receptor antagonists: a new generation of anticancer drugs.

After binding to the neurokinin-1 (NK-1) receptor, substance P (SP) induces tumor cell proliferation, angiogenesis, and the migration of tumor cells for invasion and metastasis. After binding to NK-1 receptors, NK-1 receptor antagonists inhibit tumor cell proliferation, angiogenesis and the migration of tumor cells. These antagonists are broad-spectrum antitumor drugs. In addition, in the host they display beneficial effects: anxiolytic, antiemetic, neuroprotector, nephroprotector, hepatoprotector, antiinflammatory and analgesic. In combination therapy with classic cytostatics, NK-1 receptor antagonists have synergic effects and minimize the side-effects of these classic drugs. Thus, NK-1 receptor antagonists could offer a new and promising generation of anticancer drugs.

Direct visualization of retinoic acid in the rat hypothalamus: an immunohistochemical study.

In order to increase our knowledge about the distribution of vitamins in the mammalian brain, we have developed a highly specific antiserum directed against retinoic acid with good affinity (10(-8) M), as evaluated by ELISA tests. In the rat brain, no immunoreactive fibers containing retinoic acid were detected. Cell bodies containing retinoic acid were only found in the hypothalamus. This work reports the first visualization and the morphological characteristics of cell bodies containing retinoic acid in the mammalian paraventricular hypothalamic nucleus and in the dorsal perifornical region, using an indirect immunoperoxidase technique. The restricted distribution of retinoic acid in the rat brain suggests that this vitamin could be involved in very specific physiological mechanisms.