Endogenous corticotropin-releasing factor potentiates the excitability of presympathetic neurons in paraventricular nucleus via activation of its receptor 1 in spontaneously hypertensive rats / 生理学报

It is well established that increased excitability of the presympathetic neurons in the hypothalamic paraventricular nucleus (PVN) during hypertension leads to heightened sympathetic outflow and hypertension. However, the mechanism underlying the overactivation of PVN presympathetic neurons remains unclear. This study aimed to investigate the role of endogenous corticotropin-releasing factor (CRF) on the excitability of presympathetic neurons in PVN using Western blot, arterial blood pressure (ABP) and renal sympathetic nerve activity (RSNA) recording, CRISPR/Cas9 technique and patch-clamp technique. The results showed that CRF protein expression in PVN was significantly upregulated in spontaneously hypertensive rats (SHRs) compared with normotensive Wistar-Kyoto (WKY) rats. Besides, PVN administration of exogenous CRF significantly increased RSNA, heart rate and ABP in WKY rats. In contrast, knockdown of upregulated CRF in PVN of SHRs inhibited CRF expression, led to membrane potential hyperpolarization, and decreased the frequency of current-evoked firings of PVN presympathetic neurons, which were reversed by incubation of exogenous CRF. Perfusion of rat brain slices with artificial cerebrospinal fluid containing CRF receptor 1 (CRFR1) blocker, NBI-35965, or CRF receptor 2 (CRFR2) blocker, Antisauvagine-30, showed that blocking CRFR1, but not CRFR2, hyperpolarized the membrane potential and inhibited the current-evoked firing of PVN presympathetic neurons in SHRs. However, blocking CRFR1 or CRFR2 did not affect the membrane potential and current-evoked firing of presympathetic neurons in WKY rats. Overall, these findings indicate that increased endogenous CRF release from PVN CRF neurons enhances the excitability of presympathetic neurons via activation of CRFR1 in SHRs.

Mu-opioid receptors in the paraventricular nucleus regulate ejaculatory behaviors via the sympathetic nerve system in male rats / 中华男科学杂志

Objective@#To explore the effects of the mu-opioid receptor (MOR) in the paraventricular nucleus (PVN) on the ejaculatory behaviors of male rats and its potential mechanisms.@*METHODS@#Male SD rats with normal ejaculation ability were mated with female ones in hormone-induced estrus. After bilateral PVN microinjection of D-Ala-2-Me-Phe-4-Gly-ol enkephalin (DAGO) or D-Phe-Cys-Tyr-D-Trp-Arg-Thr-Pen-Thr-NH2 (CTAP) with an inserted catheter, the male animals were observed for mount latency (ML), mount frequency (MF), intromission latency (IL), intromission frequency (IF), ejaculation latency (EL), ejaculation frequency (EF), post-ejaculation interval (PEI), and intromission ratio (IR). The lumbar sympathetic nerve activity (LSNA) of the rats was recorded using the PowerLab data acquisition hardware device, and the levels of norepinephrine (NE) in the peripheral plasma were measured by ELISA following microinjection of saline or different doses of DAGO or CTAP.@*RESULTS@#Neither CTAP nor DGAO significantly affected the ML of the male rats (P > 0.05). DGAO remarkably increased IF (P < 0.01) and MF (P < 0.01), prolonged IL (P < 0.01), EL (P < 0.01) and PEI (P < 0.01), and reduced EF (P <0.01) and IR (P < 0.05). On the contrary, CTAP markedly decreased IF (P < 0.01) and MF (P < 0.01), shortened IL (P < 0.01), EL (P < 0.01) and PFI (P < 0.01), and elevated EF (P < 0.01) and IR (P < 0.01). Additionally, DAGO decreased LSNA in a dose-dependent manner and reduced the NE level in the peripheral plasma. CTAP, however, not only offset the effects of DAGO on LSNA, but also significantly increased LSNA.@*CONCLUSIONS@#MOR in PVN inhibits ejaculatory behaviors in male rats by weakening LSNA, which has provided some theoretical evidence for the use of highly selective opioids in the treatment of premature ejaculation.

Differences in sympathetic nervous system activity and NMDA receptor levels within the hypothalamic paraventricular nucleus in rats with differential ejaculatory behavior / 亚洲男科学杂志(英文版)

Differences in intravaginal ejaculation latency reflect normal biological variation, but the causes are poorly understood. Here, we investigated whether variation in ejaculation latency in an experimental rat model is related to altered sympathetic nervous system (SNS) activity and expression of N-methyl-D-aspartic acid (NMDA) receptors in the paraventricular nucleus of the hypothalamus (PVN). Male rats were classified as "sluggish," "normal," and "rapid" ejaculators on the basis of ejaculation frequency during copulatory behavioral testing. The lumbar splanchnic nerve activity baselines in these groups were not significantly different at 1460 ± 480 mV, 1660 ± 600 mV, and 1680 ± 490 mV, respectively (P = 0.71). However, SNS sensitivity was remarkably different between the groups (P < 0.01), being 28.9% ± 8.1% in "sluggish," 48.4% ± 7.5% in "normal," and 88.7% ± 7.4% in "rapid" groups. Compared with "normal" ejaculators, the percentage of neurons expressing NMDA receptors in the PVN of "rapid" ejaculators was significantly higher, whereas it was significantly lower in "sluggish" ejaculators (P = 0.01). In addition, there was a positive correlation between the expression of NMDA receptors in the PVN and SNS sensitivity (r = 0.876, P = 0.02). This study shows that intravaginal ejaculatory latency is associated with SNS activity and is mediated by NMDA receptors in the PVN.

Serotoninergic Modulation of Basal Cardiovascular Responses and Responses Induced by Isotonic Extracellular Volume Expansion in Rats / Modulação Serotoninérgica de Respostas Cardiovasculares Basais e Induzidas pela Expansão Isotônica do Volume Extracelular em Ratos

Abstract Background: Isotonic blood volume expansion (BVE) induced alterations of sympathetic and parasympathetic activity in the heart and blood vessels, which can be modulated by serotonergic pathways. Objective: To evaluate the effect of saline or serotonergic agonist (DOI) administration in the hypothalamic paraventricular nucleus (PVN) on cardiovascular responses after BVE. Methods: We recorded pulsatile blood pressure through the femoral artery to obtain the mean arterial pressure (MAP), systolic (SBP) and diastolic blood pressure (DBP), heart rate (HR) and the sympathetic-vagal ratio (LF/HF) of Wistar rats before and after they received bilateral microinjections of saline or DOI into the PVN, followed by BVE. Results: No significant differences were observed in the values of the studied variables in the different treatments from the control group. However, when animals are treated with DOI followed by BVE there is a significant increase in relation to the BE control group in all the studied variables: MBP (114.42±7.85 vs 101.34±9.17); SBP (147.23±14.31 vs 129.39±10.70); DBP (98.01 ±4.91 vs 87.31±8.61); HR (421.02±43.32 vs 356.35±41.99); and LF/HF ratio (2.32±0.80 vs 0.27±0.32). Discussion: The present study showed that the induction of isotonic BVE did not promote alterations in MAP, HR and LF/HF ratio. On the other hand, the injection of DOI into PVN of the hypothalamus followed by isotonic BVE resulted in a significant increase of all variables. Conclusion: These results suggest that serotonin induced a neuromodulation in the PVN level, which promotes an inhibition of the baroreflex response to BVE. Therefore, the present study suggests the involvement of the serotonergic system in the modulation of vagal reflex response at PVN in the normotensive rats.

Resumo Fundamento: Expansão de volume extracelular (EVEC) promove alterações da atividade simpática e parassimpática no coração e vasos sanguíneos, os quais podem ser moduladas por vias serotoninérgicas. Objetivo: Avaliar o efeito da administração de salina ou agonista serotoninérgico (DOI) nos núcleos paraventriculares hipotalâmico (NPV) sobre respostas cardiovasculares após EVEC. Métodos: Foram obtidos registros da pressão arterial pulsátil, por meio da artéria femoral, para obtenção dos valores da pressão arterial média (PAM), sistólica (PAS), diastólica (PAD), frequência cardíaca (FC) e razão simpático-vagal (LF/HF) de ratos Wistar antes e após receberem microinjeções bilaterais no NPV de salina ou DOI seguida de EVEC. Resultados: Não foram observadas diferenças significativas dos valores das variáveis estudadas nos diferentes tratamentos do grupo controle. Entretanto, quando os animais são tratados com DOI seguida de EVEC ocorre aumento significativo em relação ao grupo controle com EVEC em todas as variáveis estudadas: PAM (114,42±7,85 vs 101,34±9,17), PAS (147,23±14,31 vs 129,39±10,70), PAD (98,01 ±4,91 vs 87,31±8,61), FC (421,02±43,32 vs 356,35±41,99) e LF/HF (2,32±0,80 vs 0,27±0,32). Discussão: O presente estudo mostrou que a indução de EVEC isotônica não promoveu alterações na PAM, PAD, PAS, FC e LF/HF. Por outro lado, os animais que receberam microinjeção de DOI no NPV seguida de EVEC apresentaram aumento significativo de todas as variáveis. Conclusão: Esses resultados sugerem que a serotonina exerce uma neuromodulação em nivel do NPV, e essa promove uma inibição da resposta barorreflexa frente à EVEC. Assim, o presente trabalho sugere o envolvimento serotoninérgico na neuromodulação no nivel do NPV na resposta reflexa vagal em ratos normotensos.

Neural regulation of the stress response: glucocorticoid feedback mechanisms

The mammalian stress response is an integrated physiological and psychological reaction to real or perceived adversity. Glucocorticoids are an important component of this response, acting to redistribute energy resources to both optimize survival in the face of challenge and to restore homeostasis after the immediate challenge has subsided. Release of glucocorticoids is mediated by the hypothalamo-pituitary-adrenal (HPA) axis, driven by a neural signal originating in the paraventricular nucleus (PVN). Stress levels of glucocorticoids bind to glucocorticoid receptors in multiple body compartments, including the brain, and consequently have wide-reaching actions. For this reason, glucocorticoids serve a vital function in negative feedback inhibition of their own secretion. Negative feedback inhibition is mediated by a diverse collection of mechanisms, including fast, non-genomic feedback at the level of the PVN, stress-shut-off at the level of the limbic system, and attenuation of ascending excitatory input through destabilization of mRNAs encoding neuropeptide drivers of the HPA axis. In addition, there is evidence that glucocorticoids participate in stress activation via feed-forward mechanisms at the level of the amygdala. Feedback deficits are associated with numerous disease states, underscoring the necessity for adequate control of glucocorticoid homeostasis. Thus, rather than having a single, defined feedback ‘switch’, control of the stress response requires a wide-reaching feedback ‘network’ that coordinates HPA activity to suit the overall needs of multiple body systems.

Effect of paraventricular nucleus lesion and cold restraint stress on gastric emptying of a liquid meal in rats

The effects of cold restraint stress on gastric emptying (GE) and the involvement of the hypothalamic paraventricular nucleus (PVN) were investigated in male Wistar rats (200-250 g body weight). Electrolytic lesions were produced stereotaxically in the nucleus by passing a 2.0-mA current for 10 s through stainless steel electrodes. GE was measured by means of a liquid test meal of 5 per cent (w/v) glucose solution plus phenol red (6 mg/dl) dye as marker, given by orogastric infusion. Cold restraint stress induces a significant increase (43.7 per cent , N = 11) in gastric retention of a 5 per cent glucose solution in rats, i.e., a delay in GE of this solution. However, restraint stress alone does not produce any change. Both truncal vagotomy and electrolytic lesion of the PVN completely block the cold restraint-induced delay in GE. However, PVN lesion per se results in a decrease of GE (30.6 per cent , N = 10) when compared to nonoperated controls. In addition, PVN-lesioned rats exposed to cold restraint present a slightly faster GE (14.7 per cent , N = 11) than controls, demonstrating an opposite response to that initially observed without lesion. These data suggest an important role for PVN efferents, probably influencing medullary vagal preganglionic neurons, in the development of this gastric motor impairment under stress conditions

Lack of similarity between the effect of lesions of the suprachcasmatic nucleus and subparaventricular hypothalamic zone on behavioral circadian rhythms

Rats were submitted to eletrolytic lesion of either the suprachiasmatic nucleus (SCN) or the subparaventricular hypothalamic zone (SPVH) and the effects on circadian behavioral rhythms were compared. While the SCN lesion abolished the circadian rythmicity of all behavioral patterns, the SPVH lesion only abolished that of the eating and drinking behavior and reduced the amplitude of a behavioral item usually associated with REM sleep