CLOMIPRAMINE INCREASES THE RESPONSIVENESS OF RAPHE-CORTICAL NEURONS IN THE RAT

The cerebral cortex of the rat possesses 5-HT1A receptor subtype; howe ver, whether the activation of this receptor by dorsal raphe nucleus s timulation produces a similar action on neuronal cortical firing as an tidepressants acting on serotonin (5-HT) function is unknown. Single-u nit extracellular recordings were obtained from parietal cortex in rat s in which dorsal raphe nucleus or cerebellar peduncle was stimulated. Results compared groups long-term treated with clomipramine (1.25 mg/ kg i.p., twice a day, during 30 days) or saline (0.15 ml i.p., twice a day, during 30 days). Amplitude of traces, firing rate, and response to treatment with clomipramine proved to be different between cortical neurons responding to dorsal raphe nucleus or cerebellar peduncle sti mulation. Clomipramine increased a long-lasting cortical suppression o f firing elicited by dorsal raphe nucleus stimulation. Obtained data s uggests that the responses of nearby cortical neurons containing diffe rent kinds of 5-HT receptors may relate to the involved pathways and t hat clomipramine seems to act on 5-HT1A receptor subtype.