Behavioural effects of phenobarbitone. 1. Effects in the offspring of laboratory mice

A mouse model of early social interactions after prenatal drug exposure: a genetic investigation

The aim of the present study was to (i) characterise the mouse behavioural profile (particularly social interactions) during the preweaning period, (ii) assess the effects of prenatal exposure to an anticonvulsant drug widely used in clinical practice, (iii) examine possible genetic differences both in baseline behavioural profiles and in sensitivity to drug-induced effects. Following a balanced intra-strain fostering procedure, the offspring of C57BL/6J and CBA inbred mouse strains from mothers exposed during pregnancy to either phenobarbitone (PHB, 60 mg/kg) or vehicle (VEH) given intraperitoneally (IP) during days 10-16 of gestation, were observed for early social interactions in the home cage during the last part of the preweaning period (days 20 and 21). The behavioural repertoires of the two strains differed markedly, in that C57 pups were more involved in Play soliciting, Locomotor-rotational play, and in Maintenance activities, while CBA mice spent much more time being inactive or exploring the environment. C57 and CBA mice also differed in the sensitivity to PHB exposure. On the whole, time spent in Investigative/Affiliative behaviours was increased, while the frequency of Play soliciting patterns was reduced in PHB-treated mice. The treatment of the fostering mother had only negligible effects, suggesting that PHB-induced changes in behaviour were largely due to direct effects of the substance on the foetus. These results indicate that specific items of the preweaning behavioural profile, and particularly social interactions, are influenced by early PHB exposure, and that the responses are heavily affected by the genotype.

Chronic administration of the 5-HT3 receptor antagonist BRL 43694; effects on reflex epilepsy and social behaviour of the Mongolian gerbil

The 5-HT3 receptor antagonist BRL 43694 was administered in drinking fluid to Mongolian gerbils, previously selected for their propensity to exhibit seizures on mild stimulation, for 11 days at doses of 1.5 micrograms/kg, 150 micrograms/kg and 1 mg/kg daily, while controls received tap water. Effects upon behaviour during encounters under white light with an untreated resident gerbil were assessed using ethological procedures. Effects upon seizure susceptibility and severity were also examined. All doses of BRL 43694 significantly increased the time spent by gerbils in the social activity "attend", and acts of social investigation involving physical contact between animals were significantly increased only by the highest dose of 1 mg/kg, as was occurrence of the specific element, "groom". The duration of flight was increased in gerbils receiving the drugs at 1.5 micrograms/kg. The treatment had no effect upon seizure susceptibility or severity. It is suggested that BRL 43694 increases the sensitivity of gerbils to their social environment. At the lower dose this was seen as an increase in flight, at all doses it was associated with increase of the social activity "attend" and at the high dose it was manifested as an increase in active social interaction. Further investigations are required to assess the relevance of these findings to the purported anxiolytic activity of 5-HT3 receptor antagonists.

Genetic differences in maternal behaviour patterns in mice administered phenobarbital during pregnancy

In a study designed to examine the role of the genotype on sensitivity to drug-induced behavioural changes, pregnant C57BL/6J and CBA mice were administered 60 mg/kg phenobarbital (PHB) intraperitoneally during days 10-16 of gestation. Following a balanced intrastrain fostering procedure, the behaviour of lactating dams was observed in their home cage at 2, 3, 5, 7 and 14 days postpartum. As the pups became older, maternal behaviour declined in control groups, whereas PHB dams of the CBA strain persisted in nursing their pups. C57 dams were generally affected in an opposite way by PHB exposure. For example, treated dams spent significantly less time in licking behaviour. Nest quality score was especially elevated in PHB dams of the CBA strain, while in C57 dams, nest-building was inhibited and nest quality unaffected by the previous PHB exposure. These results indicate that specific items of maternal behaviour can be differently affected by PHB exposure, and that the responses are affected by the genotype. To summarise, pups raised by treated dams may receive either exaggerated or insufficient maternal attention, as a result of changes in neurotransmitter systems and behavioural regulation following phenobarbital exposure. These results point to the need for a better understanding of mother/pup interactions in studies aimed at characterizing drug and toxicant effects on postnatal development.

Effects of anticonvulsant drugs on brain cultures from chick embryos: a comparison with cultures from embryos treated in ovo

The effects of anticonvulsant drugs phenytoin, phenobarbitone, and sodium valproate on neurons and glia from embryonic chicken brain have been tested. These effects have been compared with those produced in neuronal and glial cultures established from embryos that were injected with the drugs in ovo. Choline acetyl transferase activity and accumulation of gamma-aminobutyric acid were measured in neuronal cultures, and carbonic anhydrase and 2,'3'-cyclic nucleotide 3' phosphohydrolase activities were measured in glial cultures. Similarities have been observed in the morphological and biochemical changes brought about by the in vitro and in vivo treatment with the drugs. The use of in vitro cell culture systems for screening drugs for potential behavioural teratogenic effects is discussed.

Sodium valproate: effects on social behaviour and physical development in the mouse

Sodium valproate given in drinking fluid at 600 mg/l (160-180 mg/kg daily) to breeding mice did not affect fertility, birth weights or physical development of pups. Postnatal and postweaning administration of this dose also had no effects upon development or weight gain. The offspring ingested 103-158 mg/kg valproate daily after weaning. Behaviour was examined in a neutral enclosure by ethological methods. Offspring exposed to valproate in utero and throughout postnatal life showed no behavioural changes at 5 weeks, although at 15 weeks Immobility was reduced in females and Social Investigation increased. At 25 weeks when encountering mice of the opposite sex, treated males showed increase in Social Investigation and treated females increases in Other Non-social Activity. Postnatal and postweaning treatment with valproate caused behavioural changes both in juveniles and adults. After postnatal exposure, reduced Immobility with increased Social Investigation and Explore and Scan occurred at 5 and 15 weeks, at 25 weeks valproate increased Social Investigation in males encountering females and at 30 weeks enhanced Aggression in pair-housed males. Stimulation of Social Investigation was the only significant behavioural effect after postweaning exposure. Overall valproate appears to enhance behaviour stimulated by the test situation; urinary pheromones do not appear to play a part in this behavioural action.

Behavioral effects of phenobarbitone II. Effects in nursing female mice

Phenobarbitone supplied at concentrations of 187.5 mg/l and 500 mg/l (50--60 mg/kg and 120--190 mg/kg daily) in the drinking fluid of mice throughout pregnancy and lactation did not affect gestation period, numbers born or resorbed or pup weights at birth and weaning. The higher dose caused significant retardation in eye-opening, development of forelimb extension, negative geotaxis, in appearance of washing and self-grooming behaviours and in cessation of suckling. The lower dose had no detectable effects. Ethological methods were used to examine spontaneous behaviour of nursing dams within home cages on days 1, 7, 14 and 21 postpartum. Treated dams showed differences in behaviour from controls, the most marked of which were increased levels of Maternal Behaviour and decreases in Non-Social Activity in the high-dose group at day 1, and continuance of pup Nursing in both treated groups and Nest Building in the high-dose group at day 21 when controls were ceasing these behaviours. At 21 days all treated dams also showed less Immobility than controls and high-dose dams a smaller amount of pup Social Investigation. Many behavioural differences at 21 days were related to developmental delay of treated pups. Overall, phenobarbitone did not impair maternal care.