Abstract
The existence of ascending 5-hydroxytryptamine (5-HT) containing cell bodies that project from the raphe nuclei to the striatum has been established for a number of years (Dahlstrom and Fuxe, 1964). More recently it has been shown that ascending 5-HT containing neurons exert a negative tonic effect on striatal dopamine (DA) turnover (Dray, Gonye, Oakley and Tanner, 1976). This pathway possibly forms part of a regulatory system for dopaminergic neurotransmission; in accord with this view, it has been reported that unilateral lesions of the dorsal raphe result in a reduction in ipsilateral striatal 5-HT and a concomitant increase in 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) that were observed thirty days after lesioning (Nicolaou, Garcia-Munoz, Arbuthnott and Eccleston, 1979). In addition, pharmacological evidence supports the existence of a reciprocal relationship between striatal DA turnover and p- and m-tyramine (p-TA and m-TA) concentrations; the direction of these changes are such that increases in DA turnover are accompanied by a reduction in p-TA and an increase in m-TA and changes in the opposite direction occur if DA turnover is reduced (see Juorio, 1982, for a review). These data suggest that if an increase in DA turnover occurs in response to raphe lesioning, it should be accompanied by a reduction in p-TA and no change or an increase in m-TA.
Published Version
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