ELICITED PGO WAVES IN RATS - LACK OF 5-HT1A INHIBITION IN PUTATIVE PONTINE GENERATOR REGION

Pontogeniculo-occipital (PGO) waves and an elicited analogue (PGO(E)) may be recorded in the pens of rats. Cholinergic cells in the peduncul opontine tegmental (PPT) and laterodorsal tegmental (LDT) nuclei are i mplicated in the generation of PGO waves. Serotonin (5-HT) may inhibit the generation of PGO waves, and possibly PGO(E). We examined the rol e of 5-HT1A receptor mechanisms in the generation of auditory-elicited PGO(E) in rats. Administration of 8-OH-DPAT [8-hydroxy-2-(n-dipropyla mino)tetralin] into PPT did not significantly affect PGO(E) amplitude or response frequency. Binding of [H-3]CN-IMI ([H-3]cyanoimipramine) t o 5-HT uptake sites located presynaptically was used as a measure of 5 -HT innervation. Quantitative autoradiographic analysis of [H-3]CN-IMI binding indicated a moderate to low degree of 5-HT innervation of PPT and a moderately high innervation of LDT compared to the dorsal raphe nucleus (DRN). Binding of [H-3]8-OH-DPAT to 5-HT1A receptors revealed few receptor sites in PPT, and a low to moderate number of receptors in LDT compared to binding in DRN. The results suggest that inhibitory serotonergic modulation of PGO(E) is probably not mediated through a 5-HT1A receptor mechanism in PPT.