Reduction by two benzodiazepines and pentobarbitone of the multiunit activity in substantia nigra, hippocampus, nucleus locus coeruleus and nucleus raphé dorsalis of encéphale isolé rats.

Multiunit activity was recorded simultaneously in the substantia nigra pars compacta, the pyramidal layer of the hippocampus dorsalis CA 1 area, the nucleus locus coeruleus and the nucleus raphé dorsalis of encéphale isolé rats; drugs were injected intravenously in increasing doses. Chlordiazepoxide decreased multiunit activity dose-dependently to a similar extent in substantia nigra, hippocampus and dorsal raphé, but was less effective in the locus coeruleus. Midazolam reduced multiunit activity in all 4 nuclei to a similar degree and was more potent than chlordiazepoxide. Specific benzodiazepine antagonists completely reversed the effects of the two benzodiazepines. Pentobarbitone was a less potent depressant than chlordiazepoxide, and its effect was not reversed by the benzodiazepine antagonist Ro 15-1788.