α1-adrenoceptor-mediated responses in the lateral geniculate nucleus are enhanced by chronic antidepressant treatment

Abstract

Responses of single dorsal lateral geniculate neurons to iontophoretic noradrenaline, serotonin, and carbachol were studied following acute or chronic administration of tricyclic antidepressants. Long-term (15–20 day) treatment of rats with a variety of clinically effective tricyclics, including the atypical iprindole, significantly enhanced α 1-adrenoceptor mediated activations induced by noradrenaline. This change appears to require chronic treatment, since acute and short term (6–8 day) tricyclic regimens fail to consistently affect noradrenaline's action. Long term antidepressant treatment was also effective in enhancing geniculate neuron sensitivity to serotonin, in accord with previous studies, but failed to modify responses to the cholinergic agonist carbachol. It is suggested that the modulation of noradrenaline and serotonin receptor activity may represent a slowly developing action of tricyclic antidepressants which correlates with their delayed clinical effects.