Joan C. Martin

Growth, development and activity in rat offspring following maternal drug exposure

Seventy-nine Sprague-Dawley derived primimparous rats were injected subcutaneously throughout pregnancy and the nursing period with either (1) 30 mg/kg of pure nicotine, (2) 5.0 mg/kg methamphetamine HCL, (3) saline vehicle, or, (4) non-injected. Vital and developmental measures were taken on the offspring throughout the nursing period and for one additional week. Metamphetamine-injected females had a shorter, and nicotine-injected females a longer gestational period, and both gained less weight over the 21-day period than the control groups. The pups of methamphetamine and nicotine dams were significantly underweight at birth and the 28 day postnatal period and exhibited developmental delay. Male offspring were divided into behavioral, aging, and autopsy on Day 28. Male offspring of methamphetamine-injected dams remained significantly lighter in weight for the first 15 months of life (aging groups). Their counterparts in the behavioral groups and the offspring of non-injected dams exhibited significantly greater activity for eight of the first twelve monthly assessments which began at 90 days of age. Additional vital, performance, and sensory measures will continue throughout the lifespan of the animals.

Maternal ethanol consumption and hyperactivity in cross-fostered offspring

Both cross-fostered and natural-mother raised male offspring whose dams had received 8.5 g/kg/day of ethanol by intubation during the entire gestational period exhibited significantly increased locomotor activity at 2 months of age, as compared with equivalent groups whose mothers received saline intubation during that period. Weight differences were excluded as a causal factor. This lends support to the hypothesis that the direct effect of alcohol on the fetus through placental transmission is the cause of increased activity or hyperactivity in offspring. The hypotheses of genetic transmission and maternal interaction effects received no support.

Neonatal neurobehavioral outcome following prenatal exposure to cocaine

This substudy of a longitudinal prospective study was designed to assess neurodevelopmental and neurobehavioral performance in newborn infants who were maternally exposed to cocaine and other drugs of abuse or the other drugs without cocaine. Sample selection procedures were designed to permit statistical control for marijuana, alcohol, and tobacco. Cocaine was assessed with both self-report and radioimmunoassay of hair. One hundred ninety-one newborns with a mean age of 43 h were assessed for 35 to 40 min on tests of reflexes, activity level, head-turning preference, tremors, nonnutritive sucking, habituation, and state. The testers were blinded to the babys drug exposure. Cocaine-exposed newborns were developmentally at risk on the tests administered compared to infants exposed to the other three drugs alone or in some combination. A dose-response effect was found: higher amounts of cocaine were associated with higher neurobehavioral risk scores.

Conditioned Aversion in Spatial Paradigms Following Methamphetamine Injection

Three experiments were performed on Sprague-Dawley derived rats in which 3.0 mg/kg, i.p., injections of methamphetamine were paired with either, (1) a distinctive spatial enclosure, i.e., either a black or gray portion of a shuttle box with discriminably different flooring, (2) the enclosure plus 0.1% saccharin solution availability in the home cage, or (3) the enclosure plus 0.1% saccharin solution availability in that area. Following three drug pairings which alternated with saline injections paired with a different enclosure or enclosure plus H2O availability, a choice of either spatial (1), or spatial plus gustatory stimuli (2,3) which included the original CSs, were presented under non-drug, non-injection conditions. Control groups received saline injections each day under identical conditions. No aversion to the enclosed area, which had been paired with the drug was demonstrated under (1), gustatory (P=0.005) but not spatial aversion was in evidence in the second paradigm, and spatial (P=0.01) and gustatory (P<0.01) aversion was exhibited in the last study. It was concluded that subsequent aversion to distinctive spatial enclosures following methamphetamine injections was not as strong an effect as similar aversions to gustatory stimuli. Furthermore, the effect only obtained to neutral and not to preferred spatial areas at the dose level tested and in the apparatus used in those studies.

Prenatal Effects of Alcohol Abuse in Humans and Laboratory Animals

Alcohol is a teratogenic drug. When ingested during pregnancy, it readily crosses the placenta, enters the fetal circulatory system, and can be associated with a range of adverse offspring effects which span the continuum from death to subtle growth and central nervous system effects, depending on the dose, the total amount of the drug, the pattern of drug use, and the period of cell differentiation at exposure. Although the mechanisms have not been clearly delineated and other risk factors may be involved, alcohol appears to be a necessary and sufficient agent for the effects.

Life span and pathology in offspring following nicotine and methamphetamine exposure.

Seventy-nine primiparous Sprague-Dawley rats received s.c. injections of either 3.0 mg/Kg of pure nicotine, 5.0 mg/Kg of methamphetamine HCL, 5.0 MG/Kg of saline vehicle, or received no injections during the 21 day gestational and 19 day nursing period. Male offspring were divided into 3 groups at weaning. The autopsy animals (n = 80) were sacrificed at selected periods during the life span, the aging animals (n = 60) were weighed monthly until death, and the behavioral rats (n = 48) were monitored on a variety of behavioral tasks throughout their life span. Measures reported here include life span data, organ pathology and tumor formation. Significant differences among the four offspring groups were found for tumor incidence, gross pathology, and age at death in the autopsy group; and weight maintenance in the aging group.

Blood alcohol level and caloric intake in the gravid rat as a function of diurnal period, trimester, and vehicle.

Blood ethanol levels, caloric intake and weight gain were monitored over the 21-day gestational period in the gravid Sprague-Dawley rat as a function of the administration of ethanol in either a liquid diet (Ensure) or an aqueous saccharin solution. The mean daily percentage of ethanol consumed (38% vs 31%), and g/Kg of ethanol consumed (11.9 vs 9.7 g/Kg) were higher for the liquid diet group than the aqueous solution group. Ethanol consumption varied by the trimester in the Ensure but not in the saccharin solution rats. Proportional maternal weight gain, live litter size, and live litter weight did not vary as a function of the method of ethanol administration. Both groups exhibited significant diurnal periodicity in ethanol consumption, and the greatest caloric intake during the second trimester. The implications of these results for ethanol administration in gravid rats is discussed.

Maternal barbiturate administration and offspring response to shock.

Gravid Sprague-Dawley-derived rats were injected SC twice daily with either 20 or 40 mg/kg pentobarbital sodium (PT), sodium phenobarbital (PH), or the same volume of the saline vehicle on days 9–21 of pregnancy. Pair-feeding was employed. Vital, developmental, and activity measures were obtained on the neonates and locomotor activity was measured from 3–10 months of age. Avoidance was measured sequentially in a shuttle box, and in an operant chamber beginning at 3 months of age. The PH-80 dams gained less weight over the gestational period, and PH-80 and PH-40 offspring had more neonatal deaths. These male offspring were hyperactive at maturity, and PH-80 rats were initially slower to escape experimenter-initiated shock. PT exposure caused transient neonatal and juvenile hyperactivity. PT rats performed more poorly on both the conditioned avoidance and Sidman shock schedules, and had significantly lower brain: body weight ratios at 1 year of age. All four drug groups outperformed the saline offspring on subject-initiated shock schedules (punishment). Sex of offspring was determined on postnatal day 4 and the sex ratio was shifted towards male births with both drugs relative to controls.

Saccharin preferences in food deprived aging rats are altered as a function of perinatal drug exposure.

Abstract The purpose of this long-term experiment was to determine if perinatal exposure to CNS activating drugs resulted in early and/or altered onset of aging, as measured by changes in preference for preferred concentrations of saccharin solutions. Seventy-nine primiparous Sprague-Dawley rats received twice daily subcutaneous injections of either 3.0 mg/kg or pure nicotine, 5.0 mg/kg of methamphetamine HCL, 5.0 mg/kg of saline vehicle, or no injections during the 21 day gestational period and during days 3–21 of the nursing period. Twelve male offspring were randomly selected from each treatment condition, and at six months of age, they were presented with a choice of 0.20, 0.10, 0.05, 0.025, 0.01, and 0.005% of saccharin in a tap water solution and plain tap water at three month intervals. Each concentration was paired with water and presented for a 48 hr period. Eight sessions were analyzed, which spanned the ages of 15 36 months. Multivariate analyses revealed that: (1) The preference for individual saccharin concentrations across time differed as a result of maternal treatment. Differences were primarily due to the drug treatments and not to injection, (2) The pattern of saccharin preference changed over time as a function of maternal treatment but the overall level of saccharin consumption was not affected. These shifts were due to the drug treatments, not injection per se, (3) The total amount of saccharin solution consumed over time did not differ significantly among treatments, (4) The total amount of fluid consumed over the mature lifespan (saccharin solution plus water) decreased for all rats irrespective of maternal treatment. Other differences over time in total fluid consumption paralleled the saccharin index measures described above. Thus, perinatal treatment had a lasting effect upon preference for nonnutritive sweet solutions. The significance of this for aging organisms is discussed.

Growth and activity but not maturation are affected by perinatal diet

Growth, maturation and activity in Sprague-Dawley rat offspring were studied as a function of two diets which were offered both pre- and postnatally. Day 1 gravid rats were placed ad lib on either Purina chow or Ensure, a total liquid diet. Half of each group was switched to the other diet on day 21 of gestation and maintained on it through weaning. Offspring remained on the same diet until sacrificed on postnatal day 60. Seven developmental measures were assessed daily until all of the animals reached criterion. The type of diet significantly affected maternal weight gain during the second third of gestation, and neonatal weight gain as measured on days 7, 14, 21, 28 and 45. Females were affected more than were male littermates. Males were significantly heavier than female littermates at all postnatal weighings. Diet had little or no effect on the developmental measures. Male/female differences were found for voluntary activity in the wheel which was measured on day 45. The use of liquid diets in behavioral teratology studies and the wisdom of using pellet diets as a control are discussed. The possibility of substituting careful measures of growth as an alternative to developmental testing is discussed.