The involvement of noradrenergic ascending pathways in the stress-induced activation of ACTH and corticosterone secretions is dependent on the nature of stressors

Abstract

The aim of the present study was to explore in male rats the role of the catecholaminergic innervation of the hypothalamus in corticotropic and adrenal responses to different kinds of stress conditions. For this purpose, 6-hydroxydopamine (3 micrograms in 0.2 microliter saline) was stereotaxically and bilaterally infused at two levels of the main noradrenergic ascending brain stem bundle (NAB-X). The efficiency of catecholaminergic denervation of the hypothalamus was checked by measuring noradrenaline concentrations in paraventricular nuclei punches by HPLC and was confirmed by a 86% fall in noradrenaline levels of NAB-X rats killed after the stress experiments. Seven days after lesioning the NAB, sham operated controls and NAB-X lesioned animals were divided into 4 groups and submitted to 4 different stressors, i.e.: 2 min ether vapors (n = 5), 1 h immobilization (n = 7), i.v. histamine (2 mg/kg; n = 7) or i.v. insuline (10 I.U./kg; n = 8) injections. ACTH and corticosterone were measured in blood samples sequentially taken from a chronic carotid cannula, before stress and at short intervals over the 2 following hours. In comparison to the respective control groups, NAB-X dramatically reduced the ACTH response to ether (-78%) and to restraint (-53%) stress whereas the corticosterone response was affected to a lesser extent. In contrast, NAB-X slightly altered these responses in the histamine-treated group, although, surprisingly, the ACTH response tended to decrease and that of corticosterone to increase. Finally, NAB-X provoked a biphasic response to insuline-induced hypoglycemia, with a very early (5 min) rise in ACTH and corticosterone in comparison to the control group, followed by a trend to low hormonal levels up to 120 min. These results strongly suggest a differential involvement of the hypothalamic noradrenergic innervation upon the hypothalamic-pituitary-adrenal axis according to the nature of stress conditions.

Effects of 900MHz radiofrequency on corticosterone, emotional memory and neuroinflammation in middle-aged rats

“…However, previous studies showed middle-aged related differences in plasmatic CORT or corticotropin-releasing factor responses to different types of stress when compared to young animals (Nolan et al, 1991;Pisarska et al, 2000). Reports of increased CORT levels for 3 days post-stress exist (Gaillet et al, 1991;Ottenweller et al, 1994), however, in most cases, the plasmatic CORT response corresponds to a transitory peak occurring within the first 30 min post (stress) stimulus (Xu et al, 1997). Our experiments showed that the CORT release was significantly increased 30 min but not 5 or 24 hours following fear conditioning, while acute GSM exposure alone did not affect CORT in young adults.…”

Influence of juvenile housing conditions on the ventilatory, thermoregulatory, and endocrine responses to hypoxia of adult male rats

“…This result is difficult to explain at this stage because, to the best of our knowledge, this study is the first to report any effect of hypoxia on circulating estradiol levels. Functional analysis of neuroanatomical pathways linking the brain stem nuclei that receive synaptic inputs from the peripheral chemoreceptors to hypothalamic regions regulating hormone release (17,33) would likely help explain how housing had such dramatic effects on this response. That the hypoxic response pattern for testosterone was similar suggests that similar mechanisms may be involved.…”

Regulation of the adrenocorticotrophin response to stress by the central nucleus of the amygdala in rats depends upon the nature of the stressor

“…Blood was immediately centrifuged and the resulting plasma was kept at -20°C until ACTH assay. Restraint stress was performed for 2 h by wrapping the body of the rat in Elastoplast as previously described (Gaillet, Lachuer, Malaval, Assenmacher & Szafarczyk, 1991). LPS (Escherichia coli Serotype 055:B5, Sigma; 1 /tg (kg body weight)-1 diluted in 150 #u1 normal saline) was injected via the arterial cannula for 15-20 s. At the end of the experiment animals were decapitated and brains were removed and frozen.…”