EFFECTS OF CLOMIPRAMINE AND DESIPRAMINE ON A C-FIBER REFLEX IN RATS

A C-fiber nociceptive reflex evoked by electrical stimulation within t he territory of the sural nerve, was recorded from the ipsilateral bic eps femoris muscle in urethane anesthetized rats. Intravenously admini stered clomipramine and desipramine produced a dose-dependent depressi on of the C-fiber reflex. High doses of intrathecal desipramine also i nhibited the C-fiber reflex, while similar intrathecal doses of clomip ramine produced only a modest inhibition of the response. Intracerebro ventricular administration of clomipramine decreased dose-dependently the C-fiber reflex whereas intracerebroventricular desipramine increas ed this reflex. These findings suggest that tricyclic antidepressants with noradrenergic selectivity, as desipramine, inhibit the spinal pro cessing of C inputs by acting directly at the spinal cord level, while those with serotonergic spectra, as clomipramine, depress the C-fiber -evoked spinal reflex by acting at a supraspinal modulatory site. (C) 1997 Elsevier Science B.V.