Reactivity of brain benzodiazepine receptors and individual sensitivity of rats to pentylenetetrazole

The individual sensitivity of the male Wistar rats to acute pentylenetetrazole injection was studied, the density and the affinity of benzodiazepine receptors in the cerebellar cortex for 3H-diazepam was measured. It was demonstrated that the reactivity of benzodiazepine receptors underlies the individual sensitivity to pentylenetetrazole. The animals with higher sensitivity were characterized by more intensive reaction than the control and resistant animals, i.e., by an decrease in the receptors density (the initial receptors density being equal in the sensitive, resistant, and control animals). Daily injections of a subconvulsive dose of pentylenetetrazole during 24 days increase the animal sensitivity to this substance, and this was accompanied by an increase in the reactivity of benzodiasepine receptors. Later on, the produced high sensitivity became somewhat lower but persisted for 6 months. The receptors density in this period reduced almost by half. In sensitive rats, a single low dose of pentylenetetrazole injected 6 months after treatment increased the density of benzodiazepine receptors. The age-matched controls, the same acute dose of pentylenetetrazole decreased both the receptor density and affinity of their binding. It is suggested that the increase in reactivity of benzodiazepine receptors is actualized via the intracellular metabotropic feedback mechanism.