Proenkephalin, [Met]enkephalin, and oxytocin immunoreactivities are colocalized in bovine hypothalamic magnocellular neurons.

Abstract

The distribution of proenkephalin and [Met] Adsorbed antisera against oxytocin and vasopressin were generous gifts from F. Vandesande. Briefly, anti-vasopressin antiserum was adsorbed by treatment with oxytocin coupled to Sepharose 4B beads. Anti-oxytocin--antiserum was similarly treated with vasopressin-Sepharose 4B. Complete details on the preparation and specificity of these antisera have been reported (19).For the production of the anti-proenkephalin antiserum, a protein composed of the first 77-amino-acid residues of adrenal proenkephalin was purified from the adrenal medulla (16). The purified protein was injected into the popliteal lymph nodes of adult male Bourgogne rabbits. Antiserum obtained 2 wk after the third injection was found to be suitable for this study. Crossreactivity in a radioimmunoassay using this antiserum was less than 0.001% for the following peptides: [Met] 5139The 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 U.S.C. §1734 solely to indicate this fact.

Effect of naloxone on plasma concentrations of prolactin and LH in lactating sows

“…This is supported by the results of previous experiments in which bromocriptine suppressed prolactin concentrations in lactating sows without influencing LH values (Seren et al, 1984;Mattioli & Seren, 1985 (Akil, Richardson, Barchas & Li, 1978;Akil & Watson, 1980), it might be supposed that a stimulus as potent as suckling would increase the production of opiates. Anatomical bases for such an hypothesis have been shown by Martin & Vogit (1981) and Vanderhaeghen, Lostra, Liston & Rossier (1983) Ellendorff, Elsaesser, Parvizi, Schäkel & Smidt (1985) reported that oxytocin administration in sows after weaning maintains the anoestrus. These data, taken together with the finding that oxytocin can directly affect ACTH secretion through an opioid-mediated mechanism (Coirò et al, 1985), indicate that oxytocin secreted in response to suckling may be the factor, acting through an opioid-mediated mechanism, responsible for the endocrine patterns of lactating pigs.…”

Endogenous opioid peptides and hypothalamic neuroendocrine neurones

“…Neurohypophysial opioids and oxytocin secretory terminals Following the description of an enkephalin-containing pathway from the supraoptic and paraventricular nuclei to the neurohypophysis (Rossier, Battenberg, Pittman et al 1979;Micevych & Eide, 1980) it has become clear that the oxytocin and vasopressin neurones themselves contain opioid peptides. Immunocytochemical techniques have demonstrated that oxytocin neurones and secretory terminals contain immunoreactive enkephalins (Martin, Geis, Holl et al 1983;Vanderhaeghen, Lotstra, Liston & Rossier, 1983) whilst vasopressin neurones and terminals con¬ tain immunoreactive dynorphin (Watson, Akil, Fischli et al 1982). These opioid peptides are co-localized with oxytocin and vasopressin in the neurosecretory granules (Martin et al 1983;Whitnall, Gainer, Cox & Molineaux, 1983;Molineaux, Rosenberger & Cox, 1984) and are released upon depolarization of the gland (Anhut & Knepel, 1982;.…”

Central Oxytocin Mediates Inhibition of Sodium Appetite by Naloxone in Hypovolemic Rats

“…A growing body of evidence suggests that at least one aspect of OT regulation is sub served by endogenous opioid pathways [9,10], Opioid peptides are localized within magnocellular OT-synthesizing neurons [11,12], and opiate receptors have been demonstrated both in the neural lobe of the pituitary [13,14] and in the supraoptic and paraventricular nuclei of the hypothalamus [15]. Treatment with opioid antago nists such as naloxone results in a pronounced increase in the spontaneous firing activity of OT neurons and en hanced pituitary release of OT in response to a variety of stimuli, both in vivo and in vitro [16][17][18][19], Such studies have indicated that both the cell bodies and nerve termi nals of OT neurons are potential sites at which endoge nous opioid peptides may inhibit OT release.…”