Relation of Endogenous Opiates to Secretion of Gonadotropins
In recent years considerable evidence has been reported indicating that the endogenous opioid peptides (EOP) have an important role in regulating secretion of pituitary hormones. B-endorphin, the enkephalins, and dynorphin appear to be the major EOPs and all may participate in control of pituitary hormone secretion. Each of these opiates has different receptors, but can be displaced from their receptors to variable degrees by morphine (MOR) or by the specific opiate antagonists, naloxone (NAL) or naltrexone (NALT). The EOP in the hypothalamus have been shown to be strongly localized in areas that contain GnRH neurons and neurons that secrete neurotransmitters which modulate GnRH release. Their inhibitory effects on gonadotropin release appear to be exerted via hypothalamic neurotransmitters and GnRH, and not directly on the pituitary. Evidence will be presented showing that the EOP are involved in regulating both basal and altered gonadotropin secretion during different endocrine states.
KeywordsLuteinizing Hormone Gonadal Steroid GnRH Neuron Luteinizing Hormone Secretion Endogenous Opioid Peptide
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