A clinical study on the relationship between the pineal gland and the opioid system

Abstract

Recent reports point to a link between the pineal gland and the opioid system. In order to investigate this relationship, two separate studies were performed on humans. Beta-endorphin plasma levels were determined after melatonin administration (0.2 mg/kg b.w. i.m. at 2 p.m.). Melatonin serum values were evaluated after administration of FK 33-824, a met-enkephalin analogue (0.3 mg i.v. infusion at 9 a.m.). A significant decrease of beta-endorphin plasma levels was observed 120 minutes after melatonin injection. Melatonin release was stimulated by FK 33-824, with a peak at 30 minutes. The present results provide evidence of the inhibitory effect of melatonin on beta-endorphin secretion and the stimulatory action of the opioid peptides on the pineal gland. However, further studies will be required to clarify the relationship between the opioid system and the pineal gland.

Stimulation of Prolactin Secretion by Melatonin Is Not Mediated by Opioids

“…In the present study, on the other hand, no effect of mela tonin administration on plasma (3-endorphin concentra tions was detected during the test period. The discrepancy between our results and those ofLissoni et al [17] may be due to differences in the doses and mode of melatonin administration. The dose of melatonin employed in the present study, which stimulated prolactin secretion, was about 1/10 that used by Lissoni et al [17], and the serum melatonin concentrations following melatonin adminis tration were probably lower than in the study by Lissoni et al [17], since the latter authors administered melatonin intramuscularly rather than orally.…”

“…The discrepancy between our results and those ofLissoni et al [17] may be due to differences in the doses and mode of melatonin administration. The dose of melatonin employed in the present study, which stimulated prolactin secretion, was about 1/10 that used by Lissoni et al [17], and the serum melatonin concentrations following melatonin adminis tration were probably lower than in the study by Lissoni et al [17], since the latter authors administered melatonin intramuscularly rather than orally. Another possible ex planation for the lack of a significant change in plasma (3-endorphin concentrations following melatonin admin istration in the present study is the interpretation of the blood (3-endorphin concentration.…”

“…As for the effect of exogneous melatonin administra tion on plasma (3-endorphin concentrations, Lissoni et al [17] have observed a significant decrease in plasma 13-endorphin concentrations 60, 120, and 180 min after intramuscular melatonin injection (0.2 mg/kg body weight at 14.00 h). However, they did not measure plasma melatonin concentrations following melatonin injection.…”

Generation of the Melatonin Endocrine Message in Mammals: A Review of the Complex Regulation of Melatonin Synthesis by Norepinephrine, Peptides, and Other Pineal Transmitters

“…Most endorphins and Enk display a stimulatory effect on MEL synthesis in vivo (Lissoni et al, 1986;Esposti et al, 1988;Stankov et al, 1990a) and ex vivo (MEL: Stankov et al, 1990a; AA-NAT: Govitrapong et al, 1992). It has been proposed, however, that this opiateinduced stimulation occurs via NAergic transmission (Fraschini et al, 1989;Stankov et al, 1990a).…”

A role of melatonin in the treatment of low back pain

“…Механизм взаимосвязи между эндогенными опиои-дами и мелатонином подтверждается тем, что введение налоксона существенно уменьшает или полностью устра-няет антиноцицептивное действие мелатонина [14]. Не-известно, как именно осуществляется это взаимодей-ствие, однако установлено, что при введении мелатонина происходит увеличение продукции и высвобождение β-эндорфинов [15], а удаление эпифиза у мышей приво-дит к значительному уменьшению анальгетического дей-ствия морфина [16].…”