الفهرس 
Physiologic actions
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Abstract
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SUMMARY AND CONCLUSIONS
The aim of our study was to investigate the role of both endogenous and exogenous opiate peptides on the release of pituitary gonadotropic hormones, follicular stimulating hormone (FSH) and Lutineizing hormone (LH) and prolactin. The study was done on postmenopausal women (with last menstrual period less than 5 years), to avoid
the feedback control of ovarian steroids on the secretion of pituitary gonadotropic hormones as well as,the effects of oestrogens on the release of prolactin.
Two main steps were involved in the study :
1)The effects of blockage of opioid receptors by intra-venous administration of naloxone (opioid antagonist) on FSH, LH and PRL levels.
2)The effects of stimulation of opioid receptors by exogenous administration of opiates (morphine) on serum FSH, LH and PRL levels.
In each step, two doses of the drugs were used . Naloxone was administered intravenously in 4 and 8 mg bolus doses, while morphine was administered intramuscularly in 5 and 10 mg doses.
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A) The results showed that, intravenous administration of naloxone resulted in :
-A significant increase in LH level, and this increase was not dose related.
-A significant increase in serum FSH level, and this increase was potentiated by increasing the dose of naloxone.
- The increase in serum FSH level was less than the increase in LH level.
These results mean that endogenous opiate peptides exert a tonic inhibitory effect on the basal release of both gonadotropic hormones, FSH and LH.
-Contrary to these effects of naloxone on LH and FSH serum levelsnaloxone injection was found to decrease serum PRL level. The decrease in serum PRL was potentiated by increasing the dose of naloxone.
B) Stimulation of opioid receptors by exogenous opiates (morphine) resulted in:
-A significant decrease in serum LH level and this decrease was augmented by increasing the dose of morphine.
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- A decrease in serum FSH level that was significant only after administration of the large morphine dose (10 mg). The decrease in serum FSH level after morphine was more after the second hour, probably due to the longer half life of FSH.
These results confirm the inhibitory effects of opiate peptides on the release of gonadotropic hormones.
- A significant increases in serum PRL was noticed after i.m. morphine. This increase was both time and dose related.
Endogenous opioid peptides appear to affect the release of gonadotrophic hormones and prolactin on the hypothalamic, level, rather than on the pituitary itself i.e., affect the secretion of gonadotropin release hormone (GnRH) and prolactin release factor (PRL). These effects of opiate peptides appear to be mediated via neurotrans-mitters which regulate the hypophysiotropic hormones secretion from the hypothalamus. The neurotransmitters involved are biogenic amines, mainly dopamine. Evidence to date suggest that dopamine inhibits PRL release and exerts a controlling effect on LH and FSH secretion . Noradrenaline, as well as, serotonine may be also impli-cated. Opiate peptides may also act on the peptidergic
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neurones containing the hypothalamic hypophysiotropic hormones to alter their release.
Although most previous reports by several investi-gators suggest that the level of action of the opiate peptides is at the hypothalamus, yet it is proposed that such an effect should be confirmed by investigating the effects of blockade, as well as, stimulation of the opioid receptors before and after injection of GnRH.
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