Subcutaneous injections of naloxone, an opiate antagonist, lead to an increase in serum luteinizing hormone concentrations in female but not in male rats before they reach puberty. In addition, estradiol benzoate specifically blocks the luteinizing hormone response to naloxone in prepubertal female rats, suggesting that the opioid peptides have a physiological role in the endocrine events leading to sexual maturation.
The fertility and urological status of 30 male paraplegics between 20 and 47 years old with lesions between the T2 and L3 levels were examined by studying serum hormone levels (estradiol-17 beta, testosterone, prolactin, and follicle-stimulating and luteinizing hormones), sperm and semen characteristics via testicular biopsy and rectal probe electrostimulation, and urodynamic evaluation. Of the patients 13 had reflexic, 4 hyperreflexic and 13 areflexic bladders. Nine of the 13 patients with reflexic and all 4 with hyperreflexic bladders had a positive external sphincter electromyogram with detrusor-sphincter dyssynergia. When catheters were not used to collect semen during rectal probe electrostimulation, retrograde semen flow into the bladder was the rule. A total of 22 patients could tolerate rectal probe electrostimulation, while 6 who could not were injured at the T12 level or lower. Seminal emissions were obtained from 35 to 42 studies in these 22 patients. Total sperm count was variable; in 22 studies it was greater than 20 million. Progressive motility usually was low; 77 per cent of the patients had less than 20 per cent motility. Of 13 biopsy specimens obtained 6 suggested normal testicular morphology, with tubule atrophy and spermatogenic activity only mildly reduced in 6 of the remaining 7. Serum testosterone and luteinizing hormone values were significantly higher (p less than 0.05) among the paraplegic patients than among intact male volunteers of the same age range. Other serum hormone levels were unchanged. Outcome of rectal probe electrostimulation and biopsy did not relate to the number of years of patient injury. Thus, the principal deterrent to the use of semen collected by rectal probe electrostimulation from paraplegics for artificial insemination resides in a predominantly low sperm motility. Suggestions for improvement of motility include 1) great care to minimize or prevent urinary tract infections, 2) selection of medications for urinary tract care that do not compromise sperm survival and 3) prevention of sperm stagnation in lower tract storage sites, perhaps by use of periodical rectal probe electrostimulation.
Morphine sulfate was found to have a direct inhibitory effect on both basal and GnRH-stimulated LH release by cultured rat pituitary cells. The inhibitory effect of morphine on LH release was prevented by the opiate antagonist naltrexone, and treatment of cells with naltrexone or beta-endorphin antiserum significantly increased basal LH release. Also, incubation of pituitary cells with CRF caused a significant decrease in basal LH release, an effect that was reversed by naltrexone. Saturable opiate-binding sites were demonstrated in enriched gonadotrophs by [3H]etorphine binding studies. The ability of morphine to inhibit gonadotropin secretion through a direct action on pituitary opiate receptors suggests that long term exposure to exogenous opiates may suppress reproductive function at the hypophyseal level. In addition, the converse effects of CRF and naltrexone or beta-endorphin antiserum on LH release indicate that intrapituitary opioid peptides could exert a paracrine inhibitory action on the gonadotroph.
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