FURTHER-STUDIES ON THE SITE OF ACTION OF DIAZEPAM - ANTICONVULSANT EFFECT IN THE RABBIT

The site of the anticonvulsant action of diazepam was studied by direct intracerebral chemostimulation in conscious rabbits with chronically implanted cannulae and recording electrodes. To evaluate anticonvulsant effectiveness, 2 procedures were used: elevation in pentylenetetrazole (PTZ) threshold for appearance of spike activity in the EEG record; elevation in the threshold of limbic after-discharges. Diazepam was injected in 1 of 3 regions: anterior amygdaloid nucleus (AA), basal amygdaloid nucleus (AB) and dorsal hippocampus (DH). Application of diazepam in the AA strongly elevated the PTZ threshold in a reversible and dose-related manner; injections in the AB or DH were ineffective. Phenobarbital was ineffective in all regions investigated. The threshold of amygdalo-hippocampal after-discharges was elevated after application of diazepam in the AA, but not after injection in the DH. Hippocampal-amygdaloid after-discharges were not influenced by the drug from either the AA or DH. The amygdaloid nucleus, and particularly its anterior part, may play a crucial role in the anticonvulsant effect of diazepam in the rabbit.