CLOMIPRAMINE ENHANCES THE EXCITATORY ACTIONS OF DORSAL RAPHE NUCLEUS STIMULATION IN LATERAL SEPTAL NEURONS IN THE RAT

Clomipramine is a serotonin reuptake blocker which produces an increas ed rate of firing in lateral septal neurons of the rat. However, it is unknown whether the response of dorsal raphe nucleus stimulation on t he firing rate of the lateral septal neurons is modified by clomiprami ne treatment. Two programs of stimulation were employed. In the first, iterative stimulation (0.3 Hz, 1 ms, 0.1 mA) produced a complex patte rn of response in which activation responses predominated, and clomipr amine increased the duration and the firing rate of afterdischarge. In the second program a short train of pulses (300 Hz, 500 ms, 0.1 ms) w as applied to the dorsal raphe nucleus. Clomipramine increased both th e duration and the frequency of firing with respect to the saline-trea ted group. The present data show that dorsal raphe nucleus stimulation produces a long-lasting increase in the firing rate of lateral septal neurons which is enhanced by clomipramine. Since clomipramine applied to the septal area produces a decrease in firing, it is concluded tha t actions taken by clomipramine on raphe nuclei produce a disinhibitor y process in the lateral septal neurons.