Clomipramine increases the responsiveness of raphe-cortical neurons in the rat

The cerebral cortex of the rat possesses 5-HT1A receptor subtype; however, whether the activation of this receptor by dorsal raphe nucleus stimulation produces a similar action on neuronal cortical firing as antidepressants acting on serotonin (5-HT) function is unknown. Single-unit extracellular recordings were obtained from parietal cortex in rats 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 stimulation. Clomipramine increased a long-lasting cortical suppression of firing elicited by dorsal raphe nucleus stimulation. Obtained data suggests that the responses of nearby cortical neurons containing different kinds of 5-HT receptors may relate to the involved pathways and that clomipramine seems to act on 5-HT1A receptor subtype.