The effects of prostaglandins (PGs) on melatonin secretion and norepinephrine (NE) and release in rat pineal gland were examined in vitro. To study melatonin secretion, pineal explants were incubated for 6 h in tissue culture 199 medium with 1-1000 nM PGE1, PGE2, or PGF2 alpha. melatonin concentration in pineal glands and media was determined by RIA, PGE2 increased pineal and medium melatonin at all concentrations tested, with a maximum of 1 nM; PGE1 was effective only at concentrations 100-1000 times greater, whereas 100 nM PGF2 alpha gland. Exposure of pineal explants to 10 microM NE brought about a 20-fold increase in melatonin release to the medium. This effect was impaired significantly, but not blocked, by prior exposure to indomethacin, acetylsalicylic acid, or mefenamic acid at supramaximal concentrations to inhibit PG synthesis (100 microM). To examine the effects of PGs on NE release, endogenous NE stores in pineal nerve endings were labeled in vitro by incubating rat pineals with [3H]NE for 30 min. Fifty minutes later, at the time when spontaneous radioactivity efflux had leveled off, transmitter release was elicited by a 1-min exposure to 80 mM K+ (S1), and the stimulus was repeated 35 min later (S2). PGs (10-100 nM) were added to the medium 20 min before S2. Ratios between fractional release of the two consecutive stimulations (S2/S1) varied between 0.84 and 1.16 in control pineals. Only 100 nM PGE2 impaired significantly transmitter release by 40%. These results suggest that PGE2 can play a role in NE-stimulated melatonin synthesis. At greater concentrations PGE2 inhibits NE release from pineal nerve endings.

Background: The influence of long‐term opioid administration on hormonal levels is not well characterized in the literature. We previously showed that intrathecal opioid therapy significantly influences the homeostasis of immune and endocrine systems. Other authors confirmed that exogenous and endogenous opioids induce this effect. They have a cytokine‐like behavior and may function as neurotransmitters, neuromodulators or hormones, as concerning their synthesis, storage and release. Aims: To assess the effects of morphine long‐term intrathecal administration on serum levels of Gonadal, Thyroidal and Adrenal axis hormones in an elderly population affected by chronic pain; to assess the correlation between hormone levels and morphine dosage. Methods: Patients suffering from chronic non‐cancer pain with or without intrathecal drug delivery system were studied and hormonal levels were monitored, using an immunoradiometric assay kit. Results: The long‐term administration of intrathecal morphine influenced part of the endocrine system, in particular, there was a reduction of FSH and LH and an increment of GH serum levels; this effect was morphine dose dependent. Conclusion: Long‐term intrathecal opioid administration influenced FSH, LH and GH serum levels. Data on this issue are inadequately described in the literature. The finding of endocrine effects of opioid therapy, nonetheless, cannot be ignored, as it may have clinical relevance in both elderly and young population. We believe that during long intrathecal pain treatments with morphine, clinicians should be aware of both immediate and later opioids side effects, and in particular, they should monitor immune and endocrine changes.