Prolonged effects of intraventricular galanin on a 5-hydroxytryptamine(1A) receptor mediated function in the rat.

Galanin (3 nmol/rat), 2 h after its intracerebroventricular (i.c.v.) administration to male rats, attenuated the passive avoidance (PA) retention deficit induced by the 5-hydroxytryptamine (HT)(1A) receptor agonist 8-hydroxy-2-(di-N-propylamino)tetraline (8-OH-DPAT) (0.2 mg/kg) The reduction in the postjunctional 5-HT(1A) receptor-mediated response after i.c.v. galanin was not associated with changes in the mRNA levels and agonist binding properties of cortical limbic 5-HT(1A) receptors, believed to be the target receptors mediating the PA deficit caused by 8-OH-DPAT. These results suggest that acute increases of galanin transmission in vivo even after 2 h can counteract limbic 5-HT(1A) receptor-mediated responses of relevance for affective disorders without significantly affecting gene expression and binding characteristics of cortical limbic 5-HT(1A) receptors.