Roy D. Bell

Function of the male sex organs in heroin and methadone users.

The function of the secondary sex organs was found to be markedly impaired in 29 participants in a methadone maintenance program. The ejaculate volume and seminal vesicular and prostatic secretions were reduced by over 50 per cent in methadone clients, as compared to 16 heroin addicts and 43 narcotic-free controls. Serum testosterone levels were also approximately 43 per cent lower in methadone clients than in controls or heroin users. Although the sperm count of methadone clients was more than twice the control levels, reflecting a lack of sperm dilution by secondary-sex-organ secretions, the sperm motility of these subjects was markedly lower than normal. On all measures of secondary-sex-organ and testicular function, heroin addicts appeared to fall between the methadone and control subjects, but, with the exception of sperm motility, the deviation from control values did not reach statisitcal significance.

Characterization and possible opioid modulation of N-methyl-D-aspartic acid induced increases in serum luteinizing hormone levels in the developing male rat

It has been previously reported that the excitatory amino acid, N-methyl-D-aspartic acid (NMDA), elicits prompt increases in serum luteinizing hormone (LH) levels in young male rats. The present studies were carried out to determine whether the effects of NMDA on LH were mediated by the release of LHRH from the hypothalamus. We also examined whether NMDA-sensitive neuronal pathways interacted with the endogenous opioid system regulating LHRH release and the ontogeny of NMDA-evoked increases in serum LH. We found that the age-response curve for NMDA-induced increases in LH was an inverted U; at early ages (10 and 15 days) the amino acid was marginally effective in increasing LH levels, it became maximally effective from post-natal days 20-40 and thereafter rapidly lost its efficacy such that it was virtually inactive in adult animals. Dose-response curves revealed that adult animals were more than 10-fold less sensitive to NMDA than their younger counterparts. Our studies also demonstrated that NMDA increased LH via a direct effect on the hypothalamic release of LHRH since a potent LHRH antagonist competitively inhibited the effects of NMDA. Finally, we observed that morphine competitively inhibited the effects of NMDA on LH release, suggesting a relationship between NMDA-sensitive neuronal pathways and those endogenous opioid-containing systems which are known to regulate LH release.

Effects of ethanol and acetaldehyde on the biosynthesis of testosterone in the rodent testes.

Abstract The effects of ethanol and acetaldehyde on testicular steroidogenesis were examined in enzymatically dispersed cells of the rodent testes. Both drugs significantly inhibited gonadotropin-stimulated steroidogenesis, but acetaldehyde was considerably more potent (>1000 times) than ethanol. To determine the step in testosterones biosynthetic pathway which was inhibited by the two drugs, cells were incubated in the presence of [3H]pregnenolone and [3H]progesterone, and the amount of label incorporated into testosterone and its precursors was determined. Ethanol and acetaldehyde inhibited only the conversion of androstenedione to testosterone; none of the other precursors of testosterone was affected.

Morphine exerts testosterone-like effects in the hypothalamus of the castrated male rat

Previous research has indicated that endogenous opioids participate in the regulation of activity in the hypothalamic-pituitary-luteinizing hormone (LH) axis and mediate the negative feedback control exerted by testosterone. If this assumption is correct, then two predictions can be made. First, the effects of testosterone should be competitively inhibited by narcotic antagonists; and, second, opiates should mimic the acute and chronic effects of testosterone in the castrated male rat. The results of the present investigations support both of these predictions. We found that naloxone competitively antagonized the depressive effects of testosterone on serum LH in the castrated rat and, conversely, that testosterone competitively antagonized the LH-releasing properties of naloxone. In addition, morphine and testosterone both depressed serum LH levels in a dose-dependent fashion in the acutely castrated animal. Moreover, morphine was just as effective as testosterone in reversing the castration-induced fall in hypothalamic-LH-releasing hormone (LH-RH), which occurs in the chronically castrated male rat. On the other hand, morphine failed to reverse the long-term changes in pituitary LH content and increase in serum LH, which is consistent with prior observations that morphine affects only the hypothalamic aspect of the hypothalamic-pituitary-LH axis in the male rat. These results, thus, support the concept that an as yet unidentified opioid-containing neuronal system regulates activity in the hypothalamic-pituitary-LH axis and mediates the effects of testosterone on this axis.

Ethanol inhibits the naloxone-induced release of luteinizing hormone-releasing hormone from the hypothalamus of the male rat

It has been inferred that ethanol suppresses the secretion of luteinizing hormone (LH) in the male by depressing the release of LH-releasing hormone (LH-RH) from the hypothalamus. Direct support for this inference has been difficult to obtain, however, because of significant technical difficulties in measuring LH-RH release under in vivo conditions. To circumvent these problems, we made use of the opiate antagonist naloxone, as a neuroendocrine probe, to elicit the release of LH-RH under in vivo conditions. We found that ethanol was a potent suppressor of the increase in serum LH levels evoked by naloxone at extremely low blood ethanol concentrations ( less than 60 mg/dl). Furthermore, we observed that the antagonism between ethanol and naloxone appeared to be competitive in nature since a fixed dose of ethanol (1 g/kg, blood ethanol concentration 60 mg/dl) shifted the naloxone dose-response curve significantly to the right and high doses of the antagonist overcame ethanols effects. Finally, we found that the interaction between ethanol and naloxone took place at the level of the hypothalamus. Our results, therefore, seem to provide the first in vivo evidence supporting the widely-held hypothesis that ethanol reduces serum LH levels by depressing the hypothalamically-medicated release of LH-RH. The mechanisms underlying ethanols depression of naloxone-induced increases in the release of LH-RH are not fully understood at this time, but one prominent possibility is that ethanol enhances the synthesis or release of endogenous opioids which in turn override naloxones effects.

Ethanol-induced reductions in testicular steroidogenesis: Major differences between in vivo and in vitro approaches

: Although it is well established that ethanol suppresses gonadotropin- and cAMP-stimulated testicular steroidogenesis, there is not good agreement on two issues: which is the step in testosterones biosynthetic pathway affected by ethanol; and the role of alterations in the NAD+/NADH ratio in ethanols effects. In these studies, we have identified major differences between in vivo and in vitro approaches, which have previously been considered as totally equivalent experimental paradigms, which could explain these discrepancies. Under in vitro conditions, we observed that ethanol selectively inhibited the conversion of androstenedione to testosterone, but that it had a much more general effect under in vivo conditions. In addition, in agreement with other studies, NAD+ overcame ethanols effects on testicular steroidogenesis in vitro, but only when labeled or unlabeled pregnenolone was added. In the absence of added pregnenolone, NAD+ was not effective in preventing ethanols effects. Our results, thus, indicate that the differences which currently exist in the literature may be explained by the indiscriminate usage of in vivo and in vitro techniques.Although it is well established that ethanol suppresses gonadotropin- and cAMP-stimulated testicular steroidogenesis, there is not good agreement on two issues: which is the step in testosterones biosynthetic pathway affected by ethanol; and the role of alterations in the NAD+/NADH ratio in ethanols effects. In these studies, we have identified major differences between in vivo and in vitro approaches, which have previously been considered as totally equivalent experimental paradigms, which could explain these discrepancies. Under in vitro conditions, we observed that ethanol selectively inhibited the conversion of androstenedione to testosterone, but that it had a much more general effect under in vivo conditions. In addition, in agreement with other studies, NAD+ overcame ethanols effects on testicular steroidogenesis in vitro, but only when labeled or unlabeled pregnenolone was added. In the absence of added pregnenolone, NAD+ was not effective in preventing ethanols effects. Our results, thus, indicate that the differences which currently exist in the literature may be explained by the indiscriminate usage of in vivo and in vitro techniques.

Effects of phenoxybenzamine on the narcotic withdrawal syndrome in the rat

Abstract The effects of various α- and β-adrenergic blocking agents on the narcotic withdrawal syndrome in rats were determined. α-Adrenergic blockers caused a dose-dependent suppression of two behavioural responses characteristic of precipitated narcotic withdrawal in the rat: diarrhoea and, most notably, wet-dog shakes. The β-adrenergic blocker, propranolol, did not effect the expression of the narcotic withdrawal syndrome. The effects of α-blockers on withdrawal behaviour did not appear to be due to the slight degree of sedation produced by the highest doses of the drugs, because pentobarbital and promethazine, in doses sufficient to induce marked sedation and anaesthesia, did not decrease the severity of withdrawal. In fact, pentobarbital appeared to exacerbate the abstinence syndrome.

Role of nicotinamide adenine dinucleotide in ethanol-induced depressions in testicular steroidogenesis

It is rapidly becoming accepted, without direct evidence, that a change in the NAD+/NADH ratio in the testes produced by the metabolism of ethanol is the principal mechanism involved in its now well-established effects on testicular steroidogenesis. The purposes of the present studies were 2-fold: (1) to examine whether, in fact, in vivo or in vitro ethanol exposure alters the NAD+/NADH ratio in the testes; and (2) to examine the validity of previous reports in which it was found that NAD+ prevented the effects of ethanol on testicular steroidogenesis under in vitro conditions. With regard to the first objective, we found that a large dose of ethanol (2.5 g/kg) markedly reduced gonadotropin-stimulated testicular steroidogenesis in vivo in the male rat, but it did not alter the NAD+ and NADH concentrations in the testes. Similarly, extremely high ethanol concentrations (200 mM) substantially suppressed hMG-stimulated testosterone biosynthesis in in vitro Leydig cell preparations but no change in NAD+ concentration occurred; NADH levels were very low in the Leydig cell preparations (less than 2% of NAD+ levels), but did not appear to change as a function of ethanol exposure. Finally, in contrast to previously published results, we found that NAD+ (1 mM) did not prevent the in vitro effects of ethanol on cAMP-stimulated testicular steroidogenesis. Consequently, our results fail to support the hypothesis that acute in vivo or in vitro ethanol administration inhibits the biosynthesis of testosterone by altering the NAD+/NADH ratio in the testes.

Multiple Effects of Ethanol on the Hypothalamic-Pituitary Gonadal Axis in the Male

There are few physiological or biochemical processes which are not influenced in some way by acute or chronic ethanol administration. Among the more prominent affects of the drug are its effects on the endocrine system. In this paper, we would like to review several experiments we have conducted to examine the effects of ethanol on one endocrine system upon which it has particulary profound effects, the hypothalamic-pituitary-gonadal (H-P-G) axis.

Acetaldehyde Directly Inhibits the Conversion of Androstenedione to Testosterone in the Testes

The effects of ethanol and acetaldehyde on testicular steroidogenesis were examined in enzymatically dispersed cells of the rodent testes. We found that both compounds significantly inhibited the gonadotropin-stimulated biosynthesis of testosterone. Acetaldehyde was approximately 4000 times more potent than its parent compound, however. Moreover, in contrast to the effects of ethanol, acetaldehyde was effective at concentrations compatible with those found under in vivo conditions after acute ethanol administration. These data indicate that acetaldehyde is, at the least, probably an extremely important factor in the well-documented ethanol-induced inhibition of testicular steroidogenesis in vivo and further suggest that ethanol may be converted to acetaldehyde to produce its testicular toxicity. Finally, we have found that acetaldehyde blocks testicular steroidogenesis by selectively and specifically inhibiting the conversion of androstenedione to testosterone.