Effect of methadone treatment during pregnancy on the fetal testes and hypothalamus in rats

Prenatal stress and risk for psychopathology: specific effects or induction of general susceptibility?

This review focuses on prenatal stress as a risk factor for psychopathology. Evidence from animal studies is summarized, and the relevance of prenatal stress models in animals for human studies is discussed. In the offspring of prenatally stressed animals, overactivity and impaired negative feedback regulation of the hypothalamic-pituitary-adrenal axis are consistent findings and may reflect a pathophysiological mechanism involved in the development of psychopathology. Reduced activity of the opioid GABA/benzodiazepine, serotonin, and dopamine systems and increased activity of the sympathico-adrenal system have been found as well. These alterations have been linked to a diverse spectrum of psychopathology. Therefore, the evidence supports the view that exposure to prenatal stress may result in a general susceptibility to psychopathology, rather than exerting a direct effect on a specific form of psychopathology.

Does maternal stress induce abnormal descent of the testis in prepubertal rats?

OBJECTIVE

To investigate whether prenatal maternal stress, considered to alter plasma testosterone concentration and induce a lack of testosterone surge in male rat fetuses, has any effect on the growth of the processus vaginalis and testicular descent in male offspring.

MATERIALS AND METHODS

Pregnant rats were divided into two groups. In group 1, the rats were placed three times daily for 60 min each session in Plexiglas rat holders (13x6x8 cm) illuminated by two 150-W flood lights from day 14 to day 18 of gestation during the dark phase of the animals' light (12 h) and dark (12 h) cycle. In group 2, pregnant females were not handled and acted as controls. After birth, the anogenital distance of both the male and female rats was measured, and the length of the processus vaginalis was measured at 7 days of age in some rats. Thereafter, at 21, 24, 27 and 30 days of age, testicular descent was assessed in the remaining male rats.

RESULTS

In group 1, at 21, 24, 27 days of age, testicular descent was delayed in the stressed rats compared with the control rats. At 30 days of age, five of 36 stressed male offspring showed abnormal testicular descent; three testes were in the superficial inguinal position and two were above the scrotum. Both the anogenital distance and the length of the processus vaginalis were significantly less in the stressed male rats than in the controls.

CONCLUSIONS

Maternal stress induced a female-like anogenital distance in male rat fetuses, and caused delayed and abnormal descent of the testis, by inhibiting the growth of the processus vaginalis after birth. Prenatal stress may therefore be involved in the delay of testicular descent in neonatal rats by inducing a mild anti-androgenic effect in the fetus.

Prenatal naltrexone facilitates male sexual behavior in the rat

The involvement of endogenous opiates in the differentiation of sexual behavior was tested by exposing rat fetuses to continuous naltrexone during the last 9 days of gestation. Time-mated female rats received oral naltrexone, 40 mg/kg/day, via their drinking water, from gestational day 13 until parturition. Early motor development, measured by swimming ability in 7-, 9-, and 11-day-old offspring of the treated dams, was unaffected by prenatal naltrexone. Adult male offspring were given three tests of male sexual behavior, then castrated, primed with ovarian hormones, and given two tests of feminine receptivity (lordosis quotient). Prenatal naltrexone facilitated masculine behavior and suppressed feminine receptivity: latencies to first mount and to ejaculation were shorter, mount rate was higher, and lordosis quotient was lower in naltrexone-treated rats, compared with control animals. These findings implicate endogenous opiates in prenatal organization of sex-specific behavioral dispositions.

Prenatal stress alters the hypothalamic levels of methionine-enkephalin in pup rats

We examined hypothalamic Methionine-enkephalin levels in offspring (postnatal day 10) from stressed female rats in different period of gestation: Group 1, restraint stress day 2 through 6; group 2, restraint stress day 7 through 11; group 3, restraint stress day 12 through day 16 and group 4, restraint stress day 2 through day 16. The hypothalamic levels of Methionine-enkephalin (134.37 +/- 6.19 pg/mg) in the offspring of stressed females from day 2 to day 6 of gestation were significantly (p < 0.001) higher than that obtained in the control group (100.66 +/- 10.13 pg/mg). Similar results were obtained in groups 2 and 3. However, in rat pups from females stressed during 15 days of gestation (group 4) the hypothalamic levels of Methionine-enkephalin (96.5 +/- 6.33 pg/mg) were similar to that obtained in the control group (101.5 +/- 5.15 pg/mg). These results suggest that acute prenatal stress alters the endogenous opioid activity in offspring with possible resultant effects on developmental processes.

Perinatal exposure to morphine affects adult sexual behavior of the male golden hamster

Duromorph, a long-acting form of morphine, was administered to pregnant golden hamsters and/or their pups over the last 4 days of pregnancy and/or the first 4 days after birth. As adults, offspring were gonadectomized, primed with estrogen and progesterone, and tested for their ability to display feminine sexual behavior when placed with a stud male. They were then given testosterone over a 4-week period and tested for their ability to display masculine sexual behavior in the presence of a receptive female. Perinatal morphine exposure had little effect on the females' ability to display either feminine or masculine sexual behavior. In contrast, feminine sexual behavior was significantly enhanced in males exposed to morphine over the perinatal period. This suggests that exposure to opiates during the critical period of sexual differentiation may prevent the defeminization process in this species.

Prenatal stress has long-term effects on brain opiate receptors

Prenatal stress has been associated with a number of behavioral consequences including altered sensitivity to exogenous opiates. In the present study, mu opiate receptors were compared in the 42-day-old offspring from females stressed on days 15-22 of gestation and from females who were unstressed controls. Membrane homogenates from the prenatal stress group showed less binding of the mu opiate receptor ligand, [3H]DAGO in striatum but not in several other brain regions. Saturation studies suggest this difference is due to fewer striatal mu opiate receptors in offspring of prenatally stressed females. Using in vitro receptor autoradiography, the decreased binding in striatum was found mostly in the rostral striatum, extending into the nucleus accumbens with conservation of the normal anatomic distribution of receptor rich patches.

Naltrexone blocks the effects of prenatal stress on sexual behavior differentiation in male rats

The male offspring of rats stressed three times daily during days 14-21 of pregnancy were more likely to show lordotic behavior when tested in adulthood than were control males. This feminization of sexual behavior was not observed if the mothers were injected with the opioid antagonist naltrexone before being stressed. These data suggest that endogenous opioids released under conditions of stress can alter the normal process of sexual behavior differentiation in the fetal male rat.

Opiates, endorphins and the developing organism: a comprehensive bibliography

A comprehensive bibliography of the literature concerned with opiates, endorphins, and the developing organism is presented. A total of 1378 clinical and laboratory references, with citations beginning in 1875, are recorded. A series of indexed accompanies the citations in order to make the literature more accessible. These indexes are divided into clinical and laboratory topics. The clinical section is subdivided into: age of subject examined; maternal aspects; effects on the fetus; pharmacology, physiology, and the withdrawal syndrome; and "other" effects on the offspring. The laboratory section is subdivided into: type of opiate/endorphin studied; species utilized; and major subject areas explored.