Morphine withdrawal alters anterior pituitary hormone secretion, brain endopeptidase activity and brain monoamine metabolism in the rat

The effect of opium addiction on thyroid function tests

Background

A number of abnormalities has been identified among drug addicted users especially heroin addicts. However, there are a few studies to assess the opium effects on thyroid hormones. the aim of the present study is to investigate the effect of opium on the thyroid function tests.

Method

In this case–control, 50 male addicts, aged 20–50 years, with history of addiction to opium lasting more than two years, and 50 male non-addicts as control group were randomly selected. 10 cc blood sample was taken for measurements of TSH, total T4 and T3, free T4 and T3, and T3 resin uptake (T3RU) and 50 cc urine sample for opium testing.

Results

The univariate analysis revealed that there was not a significant association between opium and serum levels of T4 and TSH, but compared with control group, a slight increase in total T3 and a decrease in T3RU were observed among addicts (P < 0.05). In multivariate analysis, opium was also found to exert a lowering effect on serum free T4 level after adjusting of age and cigarette smoking (P < 0.05).

Conclusion

The findings of the present study demonstrated that opium can influence on thyroid function by increasing total T3 and decreasing T3RU and free T4 levels.

Desmopressin accelerates the rate of urinary morphine excretion and attenuates withdrawal symptoms in rats

AIM

The aim of this study was to examine the effects of desmopressin on morphine withdrawal symptoms and vasopressin level in morphine-dependent subjects.

METHODS

Wistar male rats were injected s.c. with morphine once per day for 5 consecutive days to induce morphine dependence. After morphine use ceased on day 5, an equal number of rats were assigned to one of four groups for either saline or desmopressin by either intraperitoneal (i.p.) or intracerebroventricular (i.c.v.) injection. From days 5 to 10, urine was collected daily and tested for the presence of morphine, and withdrawal symptoms were monitored to assess the effects of desmopressin.

RESULTS

Significant weight loss occurred among all morphine-addicted rats during the withdrawal period. With both methods (i.p. and i.c.v.), the period of urinary morphine excretion was shorter for the two groups that were given desmopressin (experimental groups) than the two groups that were not given desmopressin (control groups), and no significant difference in urinary morphine excretion was found between the two experimental groups. During the early stage of withdrawal, the severity of the withdrawal symptoms in the experimental groups was significantly lower than that in the control groups.

CONCLUSION

Desmopressin decreases the extent of morphine withdrawal symptoms, indicating that this agent might be appropriate for treating morphine addiction. Desmopressin appears to reduce withdrawal symptoms not by exerting an anti-diuretic effect but rather by exerting an effect on the central nervous system.

Activities of prolyl endopeptidase and dipeptidyl peptidase IV in brain structures of rats with dopamine deficiency-dependent MPTP-induced depressive syndrome

The development of MPTP-induced depressive syndrome in rats was accompanied by activation of prolyl endopeptidase and dipeptidyl peptidase IV in the brain frontal cortex. Prolyl endopeptidase activity in the striatum also increased under these conditions. Our results indicate that proline-specific peptidases in the target structures of the brain dopaminergic system are involved in the pathogenesis of dopamine deficiency-dependent depressive states.

The antinociceptive activity of kappa- but not delta-opioid receptor agonists is maintained in morphine-tolerant neuropathic rats

The antinociceptive effect of the preferential mu-opioid receptor agonist morphine (1 mg/kg i.v.), the delta-opioid receptor agonists, DTLET ([D-Thr2,Leu5]enkephalin-Thr) (3 and 6 mg/kg i.v.) and BUBUC ([D-Cys(StBu)2,Leu5]enkephalin-Thr(OtBu) (3 mg/kg i.v.), and the kappa-opioid receptor agonist U-69,593 (trans-3,4-dichloro-N-methyl-N-[7-(1-pyrrolidinyl)cyclohexil]benze neacetamide methanesulfonate) (0.25, 0.5 and 0.75 mg/kg i.v.) was evaluated in mononeuropathic (chronic constriction of the common sciatic nerve) rats. The rats were pretreated s.c. with 10 mg/kg of morphine, or saline, twice daily from day 12 to day 16 after the surgery. In morphine-pretreated rats, the antinociceptive effect of morphine on the vocalization threshold to paw pressure was greatly reduced, as compared to the saline-pretreated group. The antinociceptive effect of DTLET and BUBUC had also disappeared in the morphine-pretreated rats. By contrast, the potent antinociceptive effect of U-69,593 was not affected by the morphine pretreatment. Furthermore, the effect of U-69,593 was reversed by the specific kappa-opioid receptor antagonist nor-binaltorphimine (1 and 2 mg/kg i.v.). These results suggest that in mononeuropathic rats, morphine pretreatment results in cross-tolerance to delta- but not to kappa-opioid receptor agonists.

Neuroendocrine effects of dexmedetomidine: evidence of cross-tolerance between a mu-opioid agonist and an alpha 2-adrenoceptor agonist in growth hormone secretion of the male rat

The role of alpha 2-adrenergic receptors (adrenoceptors) in the secretion of growth hormone, prolactin and thyrotropin was studied using highly selective agonists and antagonists of the alpha 2-adrenoceptor. The interplay between opiates and alpha 2-adrenergic drugs in the acute secretion of growth hormone and prolactin, as well as the possible cross-tolerance between morphine (mu-opioid receptor agonist) and dexmedetomidine (alpha 2-adrenoceptor agonist) in growth hormone secretion were also evaluated. Dexmedetomidine dose-dependently increased plasma growth hormone and prolactin levels and decreased thyrotropin levels. The enhanced secretion of both growth hormone and prolactin was antagonized by atipamezole (an alpha 2-adrenoceptor antagonist) but not by prazosin (an alpha 1-adrenoceptor antagonist). Morphine (5 mg/kg)-induced stimulation of growth hormone secretion was antagonized by both naloxone (mu-opioid antagonist) and atipamezole. Naloxone, but not atipamezole, antagonized the morphine-induced increase in prolactin secretion. Dexmedetomidine increased growth hormone secretion in the saline pretreated rats, but did not do so in the morphine-tolerant rats. The stimulation of alpha 2-adrenoceptor enhances secretion of both growth hormone and prolactin. The adrenergic regulation of thyrotropin secretion still remains unclear. Evidently, adrenergic mechanisms are involved in the morphine-induced stimulation of growth hormone secretion, but not in the morphine-induced stimulation of prolactin secretion. In addition, there is a clear cross-tolerance between dexmedetomidine and morphine in growth hormone secretion of the rat.