Behavioral comparison of pentylenetetrazol, clonidine, chlordiazepoxide and diazepam in infant rats.

The effects of various doses of pentylenetetrazol, clonidine, chlordiazepoxide and diazepam on limb and head movement and behavioral seizure signs were examined in 4-, 8- and 16-day old rats tested at ambient temperatures of either 25 or 35 degrees C. All 4 drugs produced intense behavioral activation at the 2 younger ages but there were marked differences among them in the effects of test temperature on this activation and in the relationship between age and their activating effect. A "paradoxical" and intense behavioral energization was observed after the administration of either of the 2 benzodiazepines at 4, 8 but not 16 days, particularly at the lower test temperature. Clonidine and pentylenetetrazol were activating at all 3 ages but while clonidine had greater effect at the low test temperature, the opposite was the case after pentylenetetrazol. The effects of the benzodiazepines and clonidine were clearly distinct from those of pentylenetetrazol and this was the only drug to substantially elicit seizure signs. It is uncertain whether or not the benzodiazepines cause brain seizures in young animals. If so, then their behavioral manifestation is clearly different from that observed after pentylenetetrazol.