The effect of adrenalectomy on Fos expression in vasopressinergic and oxytocinergic neurons in response to stress in the rat

Abstract

This study evaluated the responses of vasopressin (AVP) and oxytocin (OT) neurons to alterations in hypothalamo-pituitary axis activity by adrenalectomy (ADX) or after restraint stress compared with basal conditions. Wistar male rats were perfuse-fixed by cardiac perfusion under anesthesia 3 h, 1, 3 and 14 days after ADX or Sham surgery. Coronal hypothalamic sections were used for evaluation of Fos, AVP and OT expression by immunohistochemistry. Under basal conditions and after stress, Fos-AVP double labeling showed no difference in the magnocellular subdivisions of the paraventricular nuclei (PVN) or in the supraoptic nuclei (SON), suggesting that the magnocellular AVP system is unlikely to contribute to ACTH secretion after restraint in both Sham and ADX rats. Fos-AVP double labeling in the parvocellular medial paraventricular nucleus (PaMP) in ADX groups was increased after 3 h in basal conditions, and in all periods after restraint stress. There were no differences between Sham and ADX groups in Fos-OT double labeling in any subdivision of the PVN; however, in the SON, the number of Fos-OT double labeled cells was increased at all time-points after stress in the ADX group. Fos expression was increased in the PaMP after 3 h and after restraint stress in the Sham and ADX groups, especially in the ADX group. In conclusion, Fos expression in different cell populations of the PVN can be differentially regulated by short- and long-term absence of glucocorticoid negative feedback and also by stress-related excitatory and/or inhibitory neural inputs. The Fos-AVP double labeling findings in the PaMP also indicate a minor participation of these vasopressinergic neurons in the regulation of the HPA axis after ADX.

Restraint stress activates nesfatin-1-immunoreactive brain nuclei in rats

“…This population of nes-fatin-1-ir neurons is extensively colocalized with oxytocin, AVP and cocaine- and amphetamine related transcript (CART) (Brailoiu et al, 2007; Foo et al, 2008; Kohno et al, 2008). Restraint stress induced Fos in a small proportion of mPVN neurons in agreement with previous reports (Ceccatelli et al, 1989; Dayas et al, 2001b; Laguna-Abreu et al, 2007; Miyata et al, 1995). Of the Fos-positive neurons in the mPVN, 18% in the lmPVN and 27% in the mmPVN also co-labeled for NUCB2/nesfatin-1.…”

Changes in prolactin secretion in the short- and long-term after adrenalectomy

“…Our data de monstrated a triphasic response pattern of ACTH levels induced by ADX: at first, there was a marked increase in ACTH release, leading to depletion of pituitary ACTH storage, which explains the decrease in circulating ACTH levels during the second phase. Finally, com pensatory changes occur, the most important being an increase in ACTH synthesis, as confirmed by increased pituitary ACTH content and proopiomelanocortin mRNA expression (19,24,25). These findings indicate a profound alteration in the HPA axis induced by ADX in the short and longterm.…”

“…In addition, we can not rule out that, in our model, PRL levels had already returned to basal levels. Previously, our group descri bed an increase in OT concentration 3 hours after ADX (19,24,25). It is important to point out that subcuta neous administration of oxytocin induces a reduction in basal, as well as in stressinduced prolactin secretion, in male rats (3335).…”

“…In the rat hypothalamus, prolactin immunoreactivity is detectable in the dorsomedial, ventromedial, supraoptic, and pa raventricular (16,17) nuclei. Vasopressin and oxytocin are synthesized in the magnocellular neurons located mainly in the posterior division of the paraventricular and supraoptic nuclei, and may be involved in the re gulation of prolactin secretion (18,19). Previous stu dies have clearly indicated that disturbance in water and electrolyte regulation alters adenohypophysial prolactin secretion (20).…”

Regulatory mechanism of hypothalamo-pituitary–adrenal (HPA) axis and neuronal changes after adrenalectomy in type 2 diabetes

“…Many reports have studied the effects of short-term ADX in various animal models (Scott Young III et al, 1986;Albeck et al, 1994;Schwartz et al, 1997;Laguna-Abreu et al, 2007). Although periods of corticosterone deficiency varied depending upon experimental conditions, most studies maintained corticosterone deficient periods for less than a week (Scott Young et al, 1986;Albeck et al, 1994;Schwartz et al, 1997;Nigawara et al, 2003;Wu et al, 2004;Glavas et al, 2007).…”