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Central Administration of Orexin A Suppresses Basal and Domperidone Stimulated Plasma Prolactin
Author(s) -
Russell S. H.,
Kim M. S.,
Small C. J.,
Abbott C. R.,
Morgan D. G. A.,
Taheri S.,
Murphy K. G.,
Todd J. F.,
Ghatei M. A.,
Bloom S. R.
Publication year - 2000
Publication title -
journal of neuroendocrinology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.062
H-Index - 116
eISSN - 1365-2826
pISSN - 0953-8194
DOI - 10.1046/j.1365-2826.2000.00582.x
Subject(s) - endocrinology , medicine , domperidone , orexin , prolactin , hypothalamus , dopaminergic , thyrotropin releasing hormone , neuropeptide , dopamine , chemistry , hormone , receptor
Orexin immunoreactive fibres are abundant in the hypothalamus suggesting a neuroendocrine regulatory role. Intracerebroventricular (ICV) administration of orexin A suppressed plasma prolactin in male rats by 71% at 20 min post‐injection and 83% at 90 min post‐injection (P < 0.005 vs saline at both time points). To investigate whether this effect was through the tuberoinfundibular dopaminergic (TIDA) system, a supra‐maximal dose of domperidone, a dopamine receptor antagonist, was injected intraperitoneally (i.p.) prior to ICV injection of orexin A. ICV orexin A significantly suppressed domperidone (9 mg/kg)‐stimulated plasma prolactin levels, by up to 40% (i.p. domperidone + ICV orexin A 3 nmol 34.5 ± 7.4 ng/ml and i.p. domperidone + ICV orexin A 20 nmol 43.5 ± 4.3 ng/ml, both P < 0.005 vs i.p. domperidone + ICV saline 57.9 ± 2.7 ng/ml). Orexin A, 100 n M , significantly stimulated release of neurotensin, vasoactive intestinal polypeptide, somatostatin, corticotropin releasing factor and luteinizing hormone releasing hormone, but had no effect on release of dopamine, thyrotropin releasing hormone (TRH), vasopressin or melanin‐concentrating hormone from hypothalamic explants in vitro . Orexin A did not alter basal or TRH stimulated prolactin release in dispersed pituitary cells harvested from male rats. The data suggest that ICV administration of orexin A suppresses plasma prolactin in part through a pathway independent of the dopaminergic system.