The interaction of post-weaning housing conditions and prenatal drug effects on behaviour

Use of Prescribed Psychotropics during Pregnancy: A Systematic Review of Pregnancy, Neonatal, and Childhood Outcomes

This paper reviews the findings from preclinical animal and human clinical research investigating maternal/fetal, neonatal, and child neurodevelopmental outcomes following prenatal exposure to psychotropic drugs. Evidence for the risks associated with prenatal exposure was examined, including teratogenicity, neurodevelopmental effects, neonatal toxicity, and long-term neurobehavioral consequences (i.e., behavioral teratogenicity). We conducted a comprehensive review of the recent results and conclusions of original research and reviews, respectively, which have investigated the short- and long-term impact of drugs commonly prescribed to pregnant women for psychological disorders, including mood, anxiety, and sleep disorders. Because mental illness in the mother is not a benign event, and may itself pose significant risks to both mother and child, simply discontinuing or avoiding medication use during pregnancy may not be possible. Therefore, prenatal exposure to psychotropic drugs is a major public health concern. Decisions regarding drug choice, dose, and duration should be made carefully, by balancing severity, chronicity, and co-morbidity of the mental illness, disorder, or condition against the potential risk for adverse outcomes due to drug exposure. Globally, maternal mental health problems are considered as a major public health challenge, which requires a stronger focus on mental health services that will benefit both mother and child. More preclinical and clinical research is needed in order to make well-informed decisions, understanding the risks associated with the use of psychotropic medications during pregnancy.

Prenatal antidepressant exposure: clinical and preclinical findings

Pharmacological treatment of any maternal illness during pregnancy warrants consideration of the consequences of the illness and/or medication for both the mother and unborn child. In the case of major depressive disorder, which affects up to 10-20% of pregnant women, the deleterious effects of untreated depression on the offspring can be profound and long lasting. Progress has been made in our understanding of the mechanism(s) of action of antidepressants, fetal exposure to these medications, and serotonin's role in development. New technologies and careful study designs have enabled the accurate sampling of maternal serum, breast milk, umbilical cord serum, and infant serum psychotropic medication concentrations to characterize the magnitude of placental transfer and exposure through human breast milk. Despite this progress, the extant clinical literature is largely composed of case series, population-based patient registry data that are reliant on nonobjective means and retrospective recall to determine both medication and maternal depression exposure, and limited inclusion of suitable control groups for maternal depression. Conclusions drawn from such studies often fail to incorporate embryology/neurotransmitter ontogeny, appropriate gestational windows, or a critical discussion of statistically versus clinically significant. Similarly, preclinical studies have predominantly relied on dosing models, leading to exposures that may not be clinically relevant. The elucidation of a defined teratological effect or mechanism, if any, has yet to be conclusively demonstrated. The extant literature indicates that, in many cases, the benefits of antidepressant use during pregnancy for a depressed pregnant woman may outweigh potential risks.

Effects of environmental enrichment on behavior and dopamine transporter function in medial prefrontal cortex in adult rats prenatally treated with cocaine

The present study determined if environmental enrichment modifies the effects of prenatal cocaine on open field activity, social interaction and dopamine transporter (DAT) function in the medial prefrontal cortex (mPFC) in rats. Cocaine (40 mg/kg) or saline was administered (s.c.) to pregnant dams from gestation days 8 to 20 (PCOC and PSAL, respectively). At postnatal day 25 (PND 25), female offspring from PCOC and PSAL groups were assigned to the enriched condition (EC; PCOC/EC and PSAL/EC) or impoverished condition (IC; PCOC/IC and PSAL/IC). On PND 60, 90 and 120, locomotor activity, rearing behavior and social interactions were assessed in the open field. On PND 345, rats were anesthetized, challenged with nicotine (0.4 mg/kg), and DAT function in medial prefrontal cortex (mPFC) was assessed using in vivo voltammetry. EC groups displayed decreased locomotor activity across test days, while activity in IC groups did not habituate across days. Generally, PCOC groups displayed more rearing behavior than PSAL groups. During social interaction assessment, IC groups followed their social partner more frequently than EC groups. Moreover, the PCOC/IC group initiated more play solicitations and was engaged in mutual rearing less frequently than PCOC/EC, PSAL/IC and PSAL/EC groups, indicating that epigenetic environmental factors decreased the divergent social behaviors displayed by the PCOC/IC group. Results from in vivo voltammetry experiments demonstrated differences in baseline DAT function in response to environmental enrichment in the prenatal saline groups; however, no effect of prenatal cocaine was observed under baseline conditions. Nicotine challenge unmasked an effect of prenatal cocaine on DA clearance rate in mPFC in the IC groups, which was attenuated by environmental enrichment. Taken together, PCOC/IC rats displayed divergent social interaction and altered DAT function in mPFC, whereas the PCOC/EC group generally was not different from PSAL groups, suggesting that environmental enrichment attenuates the behavioral and neurochemical effects of prenatal cocaine.

Gestational stage-specific effects of retinoic acid exposure in the rat

Although, or perhaps because, retinoids are among the earliest known behavioral teratogens, there is still little agreement about the behavioral effects of stage-specific exposure to these compounds. In these studies, pregnant albino rats were gavaged once daily with retinoic acid (RA) for 3 consecutive gestational days (GD), GD 8-10), GD 11-13, or GD 14-16. Dose levels were maximal levels compatible with survival (10, 2.5, or 12.5 mg/kg RA, over GD 8-10, 11-13, and 14-16, respectively). Two studies were conducted. The first assessed the effects of RA exposure on GD 8-10 or 14-16 on regional brain weight and on a large behavioral test battery. The second study assessed the effects of RA exposure on GD 11-13 or GD 14-16 on many of the same variables. Taken together with an earlier study of the behavioral effects of GD 11-13 RA exposure, these studies permit the following conclusions. 1) RA exposure at the above doses at any of the three exposure periods produced an apparent reduction in amphetamine-induced open field activity. 2) RA exposure on GD 14-16 but not earlier produced a robust, replicable rotarod deficit in exposed offspring. 3) RA exposure on GD 11-13, but not earlier or later, increased daytime activity in residential running wheels. 4) RA exposure on GD 11-13 or GD 14-16 but not GD 8-10 reduced weight of cerebellum. 5) No RA effect at any exposure period was seen on maze learning, activity in novel open fields, or on auditory startle.

Treatment of anxiety during pregnancy: effects of psychotropic drug treatment on the developing fetus

Pregnancy is a time of great emotional change for a woman, producing increased stress and anxiety. Medication may be required for the treatment of anxiety disorders at this time. Given the fact that psychotropic drugs readily cross the placenta and could have important implications for the developing fetus, it is necessary to balance the possible effects of medication against the potential effects to both the mother and fetus if the anxiety disorder is left untreated. Despite the widespread use of psychotropic drugs such as benzodiazepines and antidepressants during pregnancy, there is a paucity of information regarding the effect of such exposure on the developing fetus. From a review of the literature it is clear that the issue of safety of psychotropic drugs during pregnancy is far from resolved. While some of the findings from animal studies are alarming, these studies cannot be directly extrapolated to humans. In addition, varying sample sizes and multiple drug exposures further complicate interpretation of human studies. Nonpharmacological treatments such as cognitive behavioural therapy should be employed whenever possible for the treatment of anxiety disorders during pregnancy. However, if medication is required pregnant women should be prescribed the lowest dosage for the minimum amount of time.

Gestational retinoic acid exposure: a sensitive period for effects on neonatal mortality and cerebellar development

This is the first in a series of studies investigating the developmental stage-specific neurobehavioral effects of all-trans retinoic acid (RA) exposure. Because high doses of this compound are known to be lethal to the developing organism, we first conducted a dose-response study to identify RA doses that produce low enough levels of gestational/postnatal mortality to make a behavioral analysis possible in survivors. Secondarily, at doses found to produce sufficient survivors on PND 28, effects on body and regional brain weights were examined. Finally, at these doses, effects on somatic malformations were evaluated. Four separate exposure periods were analyzed: gestational days (GD) 8 through 10, 11 through 13, 14 through 16, or postnatal days (PND) 3 through 5. In the postnatal exposure period rat pups were injected (s.c.) with three consecutive daily doses of 0, 5, 10, or 20 mg/kg RA on PND 3 through 5. This postnatal exposure had no detectable effect on survival, body or brain weight. In contrast, there was a marked sensitivity to RA in the GD 11-13 group. Many pups from dams given 10 mg/kg RA PO on GD 11-13 were found dead in the cage on the day of birth, and all surviving pups died within 4 days of birth. Examination of milkbands revealed no evidence of effective suckling in these short-term survivors. The same 10 mg/kg dose at GD 8-10 or GD 14-16 produced much lower mortality and pups appeared to suckle normally. To produce adequate PND 28 survival in the GD 11-13 group, it was necessary to reduce dosage to 2.5 mg/kg daily. Even this lower exposure produced effects on PND 28 body and brain weight, significantly lowering weights of body (84% of control), whole brain (94%), and cerebellum (90%). Cerebellar weight was also depressed as percent of whole brain weight, suggesting an effect focused specifically on this region. RA at 10 or 12.5 mg/kg over GD 14-16 also reduced cerebellar weight (92% and 91% of control, respectively). Thus, exposure on GD 14-16 had effects similar to those seen at GD 11-13, but only at considerably higher doses. In contrast, exposure to RA on GD 8-10 did not affect whole body or brain weight, and of eight brain regions examined, only brain stem weight was reduced (91% of control). The GD 8-10 exposure also differed substantially from later exposures in that it was the only treatment to produce substantial malformations, including exencephaly, eye and skeletal defects. We conclude that gestational exposure to RA produces lethality and regional brain stunting that is dose and developmental stage specific, with a pronounced sensitive period on GD 11-13. In contrast, the GD 8-10 period is most sensitive for production of malformations, albeit at somewhat higher doses.

Behavioral effects of low-dose gestational day 11-13 retinoic acid exposure

In a comparison article we report that maternal PO exposure to 2.5 mg/kg all-trans retinoic acid (RA) daily for 3 consecutive days over gestational days (GD) 11-13 produces a 10% reduction in weight of cerebellum at 4 weeks of age, not accompanied by other malformations. Here we report the results of a preliminary behavioral analysis of offspring exposed gestationally to RA as above. Exposed dams were allowed to deliver normally, and litters were culled to eight pups (4 +/- 1 of each sex) at birth. Both male and female offspring were tested prior to weaning on GD 21. Thereafter females were killed on postnatal day (PND) 28 for verification of RA effects on regional brain weight, and all subsequent behavioral testing was conducted on males. Preweaning tests were restricted to negative geotaxis (PND 8-9) and open field activity (PND 22). Postweaning tests included open field activity (PND 43), auditory startle response (three times, on PNDs 22, 43, and 84), 2-week activity in residential running wheels (PNDs 62-76), complex maze performance for 5 consecutive days (PND 83-87), emergence latency (PND 106), and assessment of the behavioral response to an amphetamine challenge (PND 107). Males were then killed on PND 108 for verification of RA effects on regional brain weights. In this study, RA reduced weight of cerebellum but not striatum. Cerebellar weight was 92% of control values in PND 28 females, and this weight difference had diminished to 95% of control weight by PND 108 in males. There were no treatment effects on negative geotaxis, activity in a small open field, auditory startle amplitude, or latency to enter an illuminated alley from a dark chamber. Maze learning occurred at levels equal to or slightly better than controls. Running wheel activity was enhanced by RA exposure, whereas activity in response to an amphetamine challenge was reduced by such exposure. We conclude that RA doses low enough to produce mild weight reductions in cerebellum, without attendant malformations, can alter behavior. The precise nature of these alterations remains to be elucidated, but the findings reported here suggest that effects may be more pronounced on activity than on learning.

Prenatal exposure to antiadrenergic antihypertensive drugs: effects on neurobehavioral development and the behavioral consequences of enriched rearing

One of the beta blockers propranolol (5 or 20 mg/kg) or atenolol (5 or 20 mg/kg) or the alpha-2 agonist clonidine (20 or 100 micrograms/kg) was administered in the drinking water to pregnant Wistar rats over gestation days 1 to 21. Maternal weight gain, litter size or litter weight were unaffected as were a number of measures of physical and behavioral development. The rats were raised after weaning in either enriched or impoverished housing. At maturity, male but not female rats that had been prenatally exposed to either of the three drugs weighed less than the controls. Testing for cognitive function using an automated version of the Hebb-Williams maze indicated impaired spatial maze problem solving ability for female rats that had been exposed to propranolol (20 mg/kg) and raised in impoverishment. Generally, enriched-reared rats committed fewer errors on the maze problems. Prenatal exposure to the drugs did not alter the beneficial effects of enriched rearing on maze solving. However, clonidine-exposed (100 micrograms/kg) female rats that were raised in enrichment showed a significantly increased mortality rate. Thus, prenatal exposure to all of these drugs exerted effects which were latent, appearing in adulthood, and which were to some extent precipitated by environmental factors. We conclude that these drugs may be physical and behavioral teratogens for the rat.

Methodological proposal in behavioural teratogenicity testing: assessment of propoxyphene, chlorpromazine, and vitamin A as positive controls

Pregnant Sprague-Dawley rats received either 80 mg/kg d-propoxyphene HCl or 20 mg/kg chlorpromazine HCl or 80,000 and 160,000 IU/kg vitamin A palmitate daily between the 6th and 20th days of gestation. Vehicle control groups were similarly treated with saline or corn oil and considered as negative controls. Offspring were examined for physical landmarks, neuromotor development, and behaviour using righting reflex, swimming, negative geotaxis, open field, rotarod, water maze, and nocturnal activity. This test battery included biochemical measurements. No reduction in parental weight and physical offspring development was observed. All these treatments produced long-term changes in more than one test. Vitamin A palmitate (160,000 IU/kg) was judged as the best positive control with this test battery for future investigation of the behavioural teratology of drugs.

The effects of alcohol induced malnutrition in pregnancy on offspring brain and behavioral development

Alcohol is known to have various deleterious effects in all animals including man. The present study was designed to establish whether the effects of moderate EtOH intake during pregnancy on offspring are due to toxic effects of the substance or to nutritional changes; whether effects are long lasting or limited in duration; and whether effects are due to the prenatal action of the substance or effects persisting into the postnatal period. The findings show that the effects obtained in our study are due to malnutrition engendered in the prenatal period and are of limited duration. Since much evidence suggests that early deficits are difficult to compensate for, it is possible that the tests used with mature animals in this study may have been insensitive to residual deficits. Alternatively, rats may truly have compensated for early retardation. This does not necessarily imply that the same compensatory processes would apply in humans, where greater complexity of environmental demands is imposed from an early age.

Prenatal treatment with clomipramine has an anxiolytic profile in the adolescent rat

The tricyclic anti-depressant clomipramine (3, 10 or 30 mg/kg/day) was administered to pregnant rats between days 8 and 21 of gestation. Male pups were cross-fostered at birth and raised in litters of eight. After weaning (postnatal day 21) the offspring were raised in an enriched environment and were then subjected to a variety of behavioral tests, lasting through adolescence (days 35 to 42), and repeated in adulthood (day 70 onwards). As has been found when imipramine was administered prenatally, the offspring showed decreased rearing and less exploration; however, the latter was entirely due to more rapid habituation to the test environment. The treatment produced an anxiolytic profile when the adolescents were tested in the Social Interaction test of anxiety. Effects did not persist into adulthood, although it may be that this was the result of repeated testing.

The effects of different types of neonatal feminization and environmental stimulation on changes in sex-associated activity/spatial learning skills

This research programme commenced in West Africa, where it was found that individuals with kwashiorkor gynaecomastia were feminized. This was also reinforced by the interacting dominant maternal socialization practices (Dawson, 1966). This was confirmed with feminized responses for adult male rats, on the Tolman-Maze (Dawson, 1972), while as well confirmed neonatally, for both feminized male and female rats (Dawson, Cheung and Lau, 1973, 1975). The present experiment tests the interacting effects of various levels of environmental stimulation, high, normal and low (Levitsky and Barnes, 1972), using feminized male rats. Thus castration, oestrogen and castration, and oestrogen feminized males, were contrasted with male and female controls. The results confirmed the physiological growth curves and other anatomical differences. As well, the activity data confirmed the hypothesis, for the combined samples (where high Ns mean more reliability) and also the environmental stimulation (F ratio: d.f. 18 and 57, 11.37, p less than 0.001; low Ns here mean lower reliability). However, for the symmetrical maze, the results for the combined samples, were not as convincing as in Dawson et al. (1973, 1975), although the environmental stimulation produced significant results in many cases, including a significant interaction for the analysis of variance (F ratio: d.f. 18 and 57, 3.12 p less than 0.001).

Experimental methods in behavioral teratology

The possibility that the exposure of the embryo to certain chemical substances can lead to behavioral disturbances is known from human epidemiological studies, e.g., in chronic poisoning with mercury and ethanol. Therefore, efforts are made to develop toxicological techniques with which new behavioral teratogens can be recognized. The review describes the most important experimental methods which are presently explored, and which are based on a rich body of knowledge accumulated by experimental psychologists. Most of the tests were developed with small animals, mostly with rats. They range from a rather straightforward determination of various reflexes to complex behavioral situations involving mechanical devices, operant conditioning techniques and procedures evaluating social behavior. In applying these methods in routine toxicology, it is important to remember, that many behavioral effects determined in newborn and adult animals are subtle. Moreover, they are influenced by a large variety of environmental factors affecting the health and the behavior of the mothers and of the offspring in the early and later phases of development. Therefore, the experiments must be conducted under highly standardized conditions and must be controlled rigorously. It is concluded that the best experimental strategy for the evaluation of potential behavioral teratogens is not yet established. Therefore, it would be premature to decide on a fixed protocol to be included in routine animal safety experiments for drugs and other chemical substances.

Behavioral, biochemical and histological effects of prenatal administration of progesterone in the rat

Pregnant Wistar rats were injected with progesterone (1.5 mg/kg) between Days 8 and 21 of gestation and the behavioral, biochemical and histological effects of this treatment were observed in the offspring. The progesterone offspring weighed less than the control animals during this weaning and were retarded on one measure of exploratory activity in the open field. None of the other 29 tests used showed any significant difference apart from a 9% increase in the amount of brain DNA in the progesterone animals. It was concluded that these differences were fortuitous and that progesterone has no consistent or significant effects on brain development in rodents following prenatal administration.

The interactive effects of prenatal imipramine exposure and postnatal rearing conditions on behaviour and histology

Offspring of rats given oral doses of Saline or Imipramine (5 mg/kg) from 14-21 days prior to mating till parturition were reared, after weaning, in deprived or enriched environments. At 25-27 days and at 80-83 days the home cage behaviour of the Ss reared in the enriched environment was observed. Histological measures of brain development in both the deprived and enriched Ss were taken at the conclusion of behavioural observations. The Imipramine exposed offspring failed to show the characteristic histological changes associated with enriched rearing conditions. In addition they were behaviourally unresponsive and spent significantly less time than the Saline offspring interacting with other animals and the environment. It was argued that the physiological and behavioural unresponsiveness of the Imipramine offspring was due to a subtle teratogenic effect which prevented the Ss from interacting with the environment.