Co-expression of corticotropin-releasing factor and vasopressin immunoreactivity in parvocellular neurosecretory neurons of the adrenalectomized rat.

Abstract

To clarify the anatomical organization that allows for the synergy of vasopressin and oxytocin with corticotropin-releasing factor (CRF) in promoting adrenocorticotropic hormone secretion from the anterior pituitary, immunohistochemical double staining methods were used to compare the distribution of these peptides in the hypothalamic paraventricular nucleus of normal, colchicine-treated, and adrenalectomized male rats. In untreated animals, a few CRFstained cells were found in the parvocellular division of the paraventricular nucleus, while brightly stained oxytocin-and vasopressin-immunoreactive cells were centered in the magnocellular division. In animals treated with colchicine, an inhibitor of axonal transport, large numbers of CRF-stained cells were found in the parvocellular division of the nucleus, and 1-2% of these also stained with antivasopressin. As reported previously, a substantial number of oxytocin-stained cells, centered in a discrete anterior part of the magnocellular division, also expressed CRF immunoreactivity. In contrast, after adrenalectomy, CRF immunostaining of cells in the parvocellular division was enhanced selectively and >70% of these cells also stained positively for vasopressin. The distribution of oxytocin-stained cells was not influenced by adrenalectomy. The unusual localization of vasopressin immunoreactivity in parvocellular neurosecretory neurons in the adrenalectomized rat suggests that a single population of cells can produce CRF and vasopressin, both of which are potent promoters of adrenocorticotropic hormone secretion. These findings indicate that there is a state-dependent plasticity in the expression of biologically active peptides by individual neuroendocrine neurons.The isolation and characterization of a peptide that has potent corticotropin-releasing activity (1) has effectively ended a longstanding controversy as to whether the posterior pituitary hormone vasopressin might serve an additional role as the principal corticotropin-releasing factor (CRF) of the hypothalamus (2). Nevertheless, it is clear that both vasopressin and the related nonapeptide, oxytocin, can potentiate the effects of CRF on the release of adrenocorticotropic hormone (ACTH) from the anterior pituitary (3-5). The anatomical organization of neurons that might allow for this kind of synergy is unclear.Physiological (6) and anatomical (7-10) studies indicate that neurons delivering CRF to hypophysial portal vessels in the median eminence are concentrated in a discrete zone of the parvocellular division of the paraventricular nucleus of the hypothalamus (PVH). In contrast, most oxytocinergic and vasopressinergic neurons in the PVH of the normal rat are concentrated in an anatomically distinct magnocellular division that projects to the posterior pituitary (11,12), though a few cells of each type are scattered throughout the The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 ...

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“…Following ADX, CRH synthesizing parvocellular neurons start to produce AVP (Silverman et al, 1981;Tramu et al, 1983;Kiss et al, 1984;Sawchenko et al, 1984;Davis et al, 1986;Swanson and Simmonds, 1989;Imaki et al, 1991). The change in AVP synthesis was reversible by pretreatment with dexamethasone or corticosterone (Silverman et al, 1981;Davis et al, 1986;Swanson and Simmonds, 1989;Imaki et al, 1991).…”

A Role for Vasopressin in the Stress‐Induced Inhibition of Gonadotrophin Secretion: Studies in the Brattleboro Rat

“…Such pathways may also mediate the effects of AVP. Anatomical studies indicate that CRF-41 neurons, which may also contain AVP (38), lie in close apposition with 8-endorphinergic neurons within the hypothalamus (39). Moreover, AVP, like CRF-41 (11, 12), has been shown to stimulate the release of B-endorphin from hypothalamic tissue in vitro (40) and in vivo (41).…”

Corticotropin-releasing hormone physiology

“…With adrenalectomy, two groups noted that CRHcontaining cells of the PVH, which project to the anterior pituitary via the median eminence, acquired expression of arginine vasopressin (AVP) (9,10). This suggested that CRH and AVP might work together to stimulate the secretion of pituitary ACTH, which was subsequently shown to be correct (11).…”