Effect of quipazine on brain stem monoamine neurons histofluorescence studies

Using two fluorescence histochemical methods, formaldehyde-induced fluorescence and sucrose-potassiumphosphate-glyoxylic acid fluorescence (SPG), we studied the effect of 5-hydroxytryptamine receptor stimulation by quipazine (2-[-piperazinyl]quinoline maleate) on monoamine fluorescence in the brain stem of rats. It was found that quipazine in a dose of 5 mg/kg i.p., after 60 min, decreased noradrenaline fluorescence intensity in noradrenergic neurons of the subcoeruleus area and diminished th density of catecholamine terminals visualized in the central part of the dorsal raphé nucleus. In the principal locus coeruleus, the intensity of fluorescence in nerve cells was not changed using either method, but with the SPG procedure, diffuse fluorescence outside cell bodies was observed after quipazine. In dorsal raphé neurons, a slight increase in 5-hydroxytryptamine fluorescence intensity was observed. The results obtained indicate that quipazine, apart from its effect on 5-hydroxytryptamine neurons, may also affect certain noradrenergic neurons.