Blockade of 5-Ht3 receptors in the septal area increases Fos expression in selected brain areas.

Serotonin is widely distributed throughout the brain and is involved in a multiplicity of visceral, cognitive and behavioral responses. It has been previously shown that injections of different doses of ondansetron, a 5-HT3 receptor antagonist, into the medial septum/vertical limb of the diagonal band complex (MS/vDB) induce a hypertensive response in rats. On the other hand, administration of m-CPBG, a 5-HT3 agonist, into the MS/vDB inhibits the increase of blood pressure during restraint stress. However, it is unclear which neuronal circuitry is involved in these responses. The present study investigated Fos immunoreactive nuclei (Fos-IR) in different brain areas following the blockade of 5-HT3 receptors located in the MS/vDB in sham and in sinoaortic denervated (SAD) rats. Ondansetron injection into the MS/vDB increases Fos-IR in different brain areas including the limbic system (central amygdala and ventral part of the bed nucleus of the stria terminalis), hypothalamus (medial parvocellular parts of the paraventricular nucleus, anterodorsal preoptic area, dorsomedial hypothalamic nucleus), mesencephalon (ventrolateral periaqueductal gray region) and rhombencephalon (lateral parabrachial nucleus) in sham rats. Barodenervation results in higher Fos expression at the parvocellular and magnocellular part of the paraventricular nucleus, the lateral parabrachial nucleus, the central nucleus of amygdala, the locus coeruleus, the medial part of the nucleus of the solitary tract, the rostral ventrolateral medulla and the caudal ventrolateral medulla following 5-HT3receptor blockade in the MS/vDB. Based on the present results and previous data showing a hypertensive response to ondansetron injected into the MS/vDB, it is reasonable to suggest that 5-HT3receptors in the MS/vDB exert an inhibitory drive that may oscillate as a functional regulatory part of the complex central neuronal network participating in the control of blood pressure.

Sex differences in serum CK activity but not in glomerular filtration rate after resistance exercise: is there a sex dependent renal adaptative response?

We investigated differences in sex responses in serum CK activity and renal function measured by glomerular filtration rate (GFR) after an exercise session. Twenty-two healthy and trained volunteers (11 males and 11 females) performed 17 resistance exercises with 3 × 12 repetitions in a circuit training fashion. Subjects provided blood samples prior to exercise session, and at 24, 48, and 72 h following exercise sessions for creatine kinase and creatinine. Twenty-four-hour urine samples were collected before and 72 h after the exercise. Estimate (e) GFR was obtained by using the Chronic Kidney Disease Epidemiology Collaboration equation adjusted for males and females. After the exercise session, males showed greater serum CK activity than females (p < 0.02), serum creatinine increased 31.3 % for males and 29.8 % for females, and urinary creatinine decreased on average 5.4 % for males and 0.6 % for females, with no significant differences (p > 0.05) between sex for serum and urinary creatinine. eGFR decreased significantly for males (~10 %) and females (~8 %), but also without a difference between the sexes (p > 0.05). The correlation between CK and eGFR was significant for males (r = -0.794; p = 0.003), and females (r = -0.8875; p < 0.001). A significant negative correlation between CK activity and the eGFR indice of renal function in both males and females was observed. Additionally, the renal function compromise was similar for both sexes, despite males presenting greater exercise-induced skeletal muscle damage when compared to females.

Comparison of explosive force between young and elderly women: evidence of an earlier decline from explosive force.

The aging process causes many changes in muscle strength, and analysis of explosive force from handgrip strength seems to be useful and promising in studying the aging musculoskeletal system. Therefore, the purpose of this study was to investigate if explosive force parameters [rate of force development (RFD) and contractile impulse (CI) over the time interval of 0-200 ms from the onset of contraction] during handgrip efforts decline differently than maximum handgrip strength with increasing age. Twenty healthy young women (20-27 years) and 65 healthy elderly women, assigned into three age groups (50-64, 65-74, and 75-86 years), participated in this study. All participants performed two maximal grip attempts. Handgrip data were recorded as force-time curves, peak force, and explosive force parameters. Our results revealed that peak force decreased significantly (p < 0.05) for those who are 65 years old, while explosive force parameters decreased significantly (p < 0.05) for those aged 50 years. These data indicate that the decline in explosive grip force-generating capacity may begin earlier (i.e., for those aged 50 years old) than peak force during the aging process. Our findings suggest that the aging process reduces the explosive grip force-generating capacity before affecting peak force.

Hand dominance during constant force isometric contractions: evidence of different cortical drive commands.

The purpose of this study was to investigate force variability and sensoriomotor strategies of dominant and nondominant hands of right and left-handed subjects during a submaximal isometric force production task. Twelve right-handed adults (9 men and 3 women; 23 ± 3 year) and twelve left-handed adults (4 men and 8 women; 24 ± 3 year) performed an isometric constant force contraction sustained at 30 and 50% of maximal force for 10 s. Surface EMG signals were obtained from forearm flexors and extensors. Force signals were analyzed in the time (CV of force) and frequency (0-10 Hz) domain. The neural activation of the involved muscles was investigated from the EMG structure using the cross-wavelet spectra of the interference EMG signals of six different frequency bands of the EMG signals were quantified (5-13, 13-30, 30-60, 60-100, 100-150 and 150-200 Hz). The major findings were: (1) dominant and nondominant hands of right- and left-handed subjects exhibited similar CV of force; (2) the power spectrum of force is influenced by handedness, with greater 1-3 Hz oscillations for left-handed subjects when compared to right-handed subjects; (3) right-handed subjects have greater 30-60 Hz neuromuscular activation when compared to left-handed subjects. Our results indicate that right-handed individuals may rely preferentially in visual feedback to carry out a task with visual and proprioceptive feedback because of the left hemisphere specialization on the visuomotor control.

Estudo do envolvimento dos receptores serotoninérgicos 5-HT3 e 5-HT2C localizados na amígdala no controle da ingestão de sal em ratos / Study of the involvement of serotonin receptors 5-HT3 and 5-HT2C located in the amygdala in controlling the intake of salt in rats

Diferentes áreas do sistema nervoso central estão envolvidas no controle da ingestão de água e sal, formando uma extensa rede neural que permite respostas corretivas viscerais e comportamentais, de forma a manter a homeostasia hidrossalina. Vários estudos têm demonstrado que a ativação de algumas vias neurotransmissoras centrais tais como a serotoninérgica, a colinérgica, a angiotensinérgica, a adrenérgica, a opiatérgica, a glutamatérgica e a GABAérgica, leva a mudanças no comportamento de ingestão de água e sal. No presente trabalho, verificamos a participação dos receptores serotoninéricos dos tipos 5-HT 3 e 5-HT 2C localizados na amígdala medial (MeA) e I central (CeA) no controle da ingestão de sal em ratos sódio-depletados. Verificamos que a administração do m-CPBG, agonista dos receptores 5-HT3, na MeA inibe a ingestão de sal em ratos sódio-depletados. Este efeito antinatriorexigênico do m-CPBG parece ser devido à sua ação nos receptores 5-IHT 3, uma vez que o pré-tratamento com a ondansetrona, antagonista específico destes receptores, bloqueia a resposta antinatrioréxica do m-CPBG. A administração da ondansetrona sozinha não foi capaz de alterar a ingestão de sal em ratos sódio-depletados. Além disso, verificamos que a injeção do m-CPP, agonista dos receptores 5-HT 2C, na MeA não alterou a ingestão de sal induzida por depleção de sódio. Ao contrário, o tratamento com o SDZ-SER082, antagonista dos receptores 5-HT 2C, inibiu a ingestão de sal quando injetado na MeA. O efeito inibitório do m-CPBG e do SDZ-SER 082 na MeA não parece ser conseqüência de efeitos aversivos ou de alterações locomotoras produzidas pela administração destas drogas. Na CeA, a administração do m-CPBG também induziu uma redução na ingestão de sal e este efeito também foi bloqueado pelo pré-tratamento com a ondansetrona. A administração de ondansetrona sozinha na CeA não alterou a ingestão de sal em ratos sódio-depletados. Além disso, verificamos que o efeito inibitório na ingestão de sal induzido pela administração do m-CPBG na CeA não está relacionado a efeitos aversivos, deficits locomotores ou ao aumento na pressão arterial. O m-CPP e o SDZ SER 082 não modificaram j a ingestão de sal em animais depletados de Sódio, quando injetados na CeA. Desta forma, podemos dizer que a estimulação farmacológica dos receptores 5-HT 3 localizados na MeA e CeA induz um significante efeito antinatriorexigênico em ratos sodio-depletados e que a integridade funcional dos receptores 5-HT 2C localizados na MeA é importante para a expressão do apetite por sódio neste modelo experimental.