Onset Of Restraint Stress Research Articles

Restraint stress-induced expression of <i>Fos</i> and several related genes in the hypothalamus of the hypertensive ISIAH rats

Stress can play a significant role in the development of arterial hypertension and many other complications of cardiovascular diseases. Considerable attention is paid to the study of the molecular mechanisms involved in the body’s response to stressful influences, but there are still many blank spots in understanding the details. ISIAH rats model a stress-sensitive form of arterial hypertension. ISIAH rats are characterized by genetically determined enhanced hypothalamic-adrenal-cortical and sympathetic adrenomedullary systems activity, which suggests a functional state of increased stress reactivity. In the present study, for the first time, the time course of the Fos and several related genes’ expression was studied in the hypothalamus of adult male hypertensive ISIAH rats after exposure to a single restraint stress of different duration (30, 60, and 120 minutes). The results of the study showed the activation of Fos transcription with a peak 1 hour after the onset of restraint stress. The dynamics of Fos gene activation coincides with the dynamics of blood pressure increase after stress. Restraint stress also alters the transcription of several other genes encoding transcription factors (Jun, Nr4a3, Jdp2, Ppargc1a) associated with the development of cardiovascular diseases. Since Fos induction is a marker of brain neuron activation, we can conclude that increased stress reactivity of the hypothalamic-pituitary-adrenocortical and sympathoadrenal systems of hypertensive ISIAH rats during short-term restriction is accompanied by activation of hypothalamic neurons and increased blood pressure level.

Restoration of neuroendocrine stress response by glucocorticoid receptor or GABA(A) receptor antagonists after experimental traumatic brain injury.

We previously reported that traumatic brain injury (TBI) produced by moderate controlled cortical impact (CCI) attenuates the stress response of the hypothalamic-pituitary-adrenal (HPA) axis between 21 and 70 days postinjury and enhances the sensitivity of the stress response to glucocorticoid negative feedback. In the current study, we investigated two possible mechanisms for the CCI-induced attenuation of the HPA stress response-i.e, glucocorticoid receptor (GR) and GABA-mediated inhibition of the HPA axis, with the GR antagonist, mifepristone (RU486), or the GABA(A)-receptor antagonist, bicuculline. In addition, we examined the effect of moderate CCI on GR and inhibitory neurons histologically in subfields of the hippocampus, medial prefrontal cortex, and amygdala. We show that at 30-min after onset of restraint stress, GR as well as GABA antagonism with MIFE or BIC, respectively, reversed the attenuating effects of moderate CCI on the stress-induced HPA response. Our histological results demonstrate that moderate CCI led to a loss of glutamic acid decarboxylase 67 or parvalbumin-positive inhibitory neurons within regions of the hippocampus and amygdala but did not lead to significant increases in GR in these regions. These findings indicate that suppression of the stress-induced HPA response after moderate CCI is mediated by the inhibitory actions of both GR and GABA, with a corresponding loss of inhibitory neurons within brain regions with neural pathways affecting limbic stress-integrative pathways.

Restraint stress up-regulates expression of zinc transporter Zip14 mRNA in mouse liver

The zinc concentration in the liver was significantly higher in mice at 12 h after the onset of restraint stress than that without stress. The IL-6 protein level in the serum was transiently elevated at 3 h after the onset of restraint stress, and the IL-6-responsive zinc transporter Zip14 mRNA in the liver was expressed markedly at 6 h. These results suggest that Zip14 plays a major role in the mechanism responsible for accumulation of zinc in the liver under restraint stress.

Sex Differences in the Stress-Induced Release of Acetylcholine in the Hippocampus and Corticosterone from the Adrenal Cortex in Rats

To assess sex differences in stress-induced acetylcholine (ACh) release in the hippocampus and corticosterone (CS) release from the adrenal cortex, an in vivo microdialysis study was performed in intact male (n = 6) and cycling female (diestrus 1, n = 5; proestrus, n = 6) rats. Dialysates and blood samples were taken from 11.00 to 16.00 h in freely moving rats, but restraint stress was applied from 12.00 to 13.00 h. Basal ACh release in the hippocampus was low without significant differences between groups. Although ACh release promptly increased with the onset of restraint stress in both sexes, the magnitude of the increase in males was significantly greater than in female rats during diestrus and proestrus (p < 0.01). Basal serum CS concentrations were significantly greater in proestrus than in diestrus (p < 0.01) or in male rats (p < 0.01). Serum CS concentrations significantly increased at the onset of restraint stress in both sexes (p < 0.01), but the magnitude of the increase was significantly greater in female than in male rats (p < 0.01). These results indicate that sex and/or gonadal steroid environment can affect the stress-induced ACh release in the hippocampus and CS release from the adrenal cortex.

Strain difference in pituitary-adrenal axis between Wistar-Imamichi and Long Evans adult male rats.

In the present study, we used closed colony-Wistar-Imamichi (WI), inbred WI and Long Evans (LE) adult male rats to examine the secretion of ACTH and corticosterone in response to restraint stress. Blood (0.3 ml) was withdrawn through a jugular cannula at 0, 15, 30, 60 and 120 min after the onset of restraint stress. Plasma concentrations of ACTH and corticosterone increased after stress in all groups, but the responses of ACTH and corticosterone secretion were higher in LE rats than in WI rats. Present data suggest that the LE rat might be a good model as a high-response strain and the closed colony or the inbred WI rat might be a good model as a low-response strain in restraint stress experiments.

Chlordiazepoxide attenuates stress-induced activation of neurons, corticotropin-releasing factor (CRF) gene transcription and CRF biosynthesis in the paraventricular nucleus (PVN).

Corticotropin-releasing factor (CRF) plays a role in coordinating endocrine, autonomic, and behavioral responses to stressful stimuli. Benzodiazepines exert many effects which oppose those of CRF, including anxiolysis and suppression of the pituitary-adrenal axis. In the present study, we employed in situ analysis of CRF heteronucleous RNA (hnRNA) and c-fos mRNA to assess stimulus-induced CRF gene transcription rate following stress and its modulation by chlordiazepoxide (CDP). Male albino rats were exposed to restraint stress for 30 min and sacrificed 30 and 120 min after the onset of stress. Either CDP or vehicle was given intraperitoneally 60 min before stress. To determine plasma ACTH levels by immunoradiometric assay, another group of rats was decapitated 10 min after the onset of restraint stress. Restraint stress induced rapidly and significantly c-fos mRNA and CRF hnRNA expression in the PVN at the 30 min time point. Increases in both RNA copies were significantly inhibited by administration of CDP at doses of 5 and 10 mg/kg. CRF mRNA concentrations were increased significantly in the PVN 120 min after stress and again, CDP attenuated significantly these increases in the PVN. The plasma ACTH increase in response to stress was inhibited significantly by CDP administration at every dose tested. CDP did not change CRF mRNA levels in the non-stressed animal.(ABSTRACT TRUNCATED AT 250 WORDS)

Stress and ACTH increase circulating concentrations of 3α-androstanediol in female rats

The present experiments were carried out to determine what physiological conditions are responsible for the acute increases in serum levels of 5α-androstane-3α, 17β-diol (3α-androstanediol, 3α-Adiol) which are seen in the intact estrous female rat within 15–30 min after mating (1). Blood samples were obtained from proestrus rats immediately before and 20 min after injection of exogenous hormones or initiation of stress procedures, and plasma concentrations of 3α-Adiol and/or progesterone (P) were measured in these samples by RIA. Intravenous injections of ovine LH (5, 15, or 45 μg) or saline resulted in equivalent significant increases in plasma 3α-Adiol 20 min after injection. In contrast, dose-dependent increases in 3α-Adiol were seen after intravenous injection of 0 (acidic saline vehicle), 2, 4, or 8 ng ACTH 1–24 to dexamethasone-pretreated rats. The highest ACTH 1–24 dose also resulted in a significant increase in plasma P concentration. In a third experiment, a significant increase in 3α-Adiol concentration above baseline was seen at 20 min after onset of restraint stress; in this case plasma P concentrations did not increase significantly. Finally, blood samples were obtained after onset of ether/jugular venipuncture stress two days after ovariectomy (ovx), adrenalectomy (adx), or ovx+adx on diestrus. The plasma 3α-Adiol response to stress was normal in intact sham-operated and non-operated groups of controls, but was significantly diminished in the ovx and the adx groups to 28.4% of that shown by the intact animals. Circulating 3α-Adiol concentrations were undetectable in 22/26 samples obtained in the ovx-adx group. These data demonstrate that plasma concentrations of 3α-Adiol increase in response to stress or ACTH but not LH, and that both the ovary and the adrenal contribute to this increase.

Effect of acute ether or restraint stress on plasma corticotropin-releasing hormone, vasopressin and oxytocin levels in the rat.

Ether and restraint stress-induced peripheral plasma corticotropin releasing hormone (CRH), arginine vasopressin (AVP), oxytocin (OXY) and adrenocorticotropin (ACTH) levels were measured by radioimmunoassays. Plasma CRH, AVP, OXY and ACTH rose to approximately twice the level of control rats 2 min after the onset of a 1-min exposure to ether. Plasma CRH rose further 5 min after the onset of ether stress, while plasma AVP and OXY returned to the baseline levels at 5 min. Plasma CRH, OXY and ACTH showed significant elevation 2 min after the onset of restraint stress, while plasma AVP did not show a significant change. Plasma OXY and ACTH rose further 5 min after the onset of restraint stress, whereas plasma CRH returned to baseline levels. CRH and OXY concentrations in the hypothalamic median eminence decreased 5 min after the onset of ether exposure and restraint, while the AVP concentration did not differ from control levels. The results, including the discrepancy between plasma CRH and ACTH 5 min after stress, suggest that CRH in the peripheral plasma is derived from both hypothalamic and extrahypothalamic tissues. The levels of stress-induced CRH in the peripheral plasma were sufficient to stimulate ACTH release. These results suggest that ether and restraint stress elevate plasma CRH shortly after the onset of the stress, and that this elevation in the plasma CRH level is at least partly responsible for stress-induced ACTH secretion.