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Stimulation of beta-endorphin and beta-lipotropin release from the anterior but not the neurointermediate pituitary lobe in the rat after acute administration of serotonin-acting drugs



Stimulation of beta-endorphin and beta-lipotropin release from the anterior but not the neurointermediate pituitary lobe in the rat after acute administration of serotonin-acting drugs



Life Sciences 31(25): 2809-2818



The respective contribution of the anterior (AP) and the neurointermediate (NIL) lobes of the pituitary gland to changes occurring in plasma .beta.-endorphin (.beta.-EP) and .beta.-lipotropin (.beta.-LPH) titers was evaluated in the rat after administration of serotonin(5-HT)-acting drugs. .beta.-EP-like immunoreactivity (.beta.-EP-LI) was concurrently evaluated in the mediobasal hypothalamus (MBH). The administration of 50 mg/kg DL-5-hydroxytryptophan (5-HT) or 12.5 mg/kg fluvoxamine, a 5-HT reuptake blocker, decreased markedly .beta.-EP-LI in the AP and induced a striking rise in plasma .beta.-EP and .beta.-LPH concentrations. Combined administration of fluvoxamine and 5-HTP failed to potentiate the effect of individual treatments. Similarly, administration of 5.0 and 10 mg/kg quipazine, a 5-HT receptor agonist, evoked a marked decrease in .beta.-EP-LI in the AP and a concomitant rise in .beta.-EP and .beta.-LPH concentrations in the plasma, while administration of 1.0 and 5 mg/kg of chlorophenylpiperazine, a weak 5-HT stimulant drug, did not alter the above indices. None of these treatments significantly altered .beta.-EP-LI in the NIL and only the higher dose of quipazine increased it in the MBH. Brain serotonin neurons apparently exert a stimulatory influence on .beta.-EP and .beta.-LPH release from the AP but, likely, not from the NIL and hypothalamic endorphins are not implicated in the secretory events occurring at the AP level after acute activation of 5-HT neurotransmission.

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Accession: 006481130

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PMID: 6298530


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