I. Cortese

Effects of morphine and chlordiazepoxide on locomotor activity in two inbred strains of mice

Summary The effects of morphine, given alone and in combination with chlordiazepoxide, have been investigated in the inbred strains of mice DBA/2J (DBA) and C57BL/6J (C57). Morphine increased the spontaneous locomotor activity only in the C57 strain, whereas no effect was found when it was administered to the DBA strain. Chlordiazepoxide, at dose levels which did not influence the locomotion, significantly increased the locomotor activity of DBA mice when given in combination with morphine. Conversely, chlordiazepoxide, at each dose tested in the present study, did not enhance the stimulation of locomotor activity elicited by morphine in the C57 strain.

Effects of morphine and chlordiazepoxide on avoidance behaviour in two inbred strains of mice.

Abstract Morphine and chlordiazepoxide were tested in the inbred strains of mice DBA/2J (DBA) and C57BL/6J (C57), subjected to three daily 50-tria1 avoidance sessions in the shuttle-box. The DBA strain reached higher avoidance levels in comparison to the C57 strain after the administration of saline. Morphine facilitated avoidance responding in the C57 strain but not in DBA mice. An improvement in avoidance behaviour was observed following the administration of chlordiazepoxide in both strains of mice. Some favourable effects were obtained in DBA mice by combining morphine with chlordiazepoxide, whereas no interaction between these drugs was found in the C57 strain.

Behavioural changes in offspring of rats exposed to diazepam during gestation

Primiparous pregnant Sprague-Dawley dams were administered a single daily s.c. injection of diazepam (0.1 and 1 mg/kg) or vehicle over gestation days 14-20. No differences in neonatal mortality and weight gain were found between the control and diazepam-exposed pups. Conversely, male pups prenatally treated with this benzodiazepine exhibited subtle behavioural alterations either during early postnatal life or during adulthood. In particular, a significant decrease in the locomotor activity of the diazepam-treated groups was found at the end of the second postnatal week (14-16 days). Furthermore, the administration of diazepam during gestation produced marked changes in the length of ultrasonic calls of rat pups removed from their nest. Finally, adult male rats (120 days of age) prenatally exposed to diazepam showed a notable impairment in copulatory activity as well as a significant decrease in the duration of ultrasonic (22 kHz) post-ejaculatory calls emitted during sexual behaviour. These findings suggest that late gestational exposure to diazepam induces both short- and long-term behavioural changes in rat offspring, changes characterized by altered activity patterns and emotional-motivational responsiveness to environmental challenges.