Has the raphe dorsalis nucleus an asymmetric function?

Differential pulse voltammetry (DPV) was used to measure 5-hydroxyindoles in the striata of anaesthetized rats. The amplitude of the voltammetry peaks in both striata decreased when 5-hydroxytryptophan (5-HTP) or 5-hydroxytryptamine (5-HT) was injected into the left side of the raphe dorsalis nucleus (RDN), but increased when either substance was injected into the right side. These findings indicate that the 5-hydroxyindole based communication between the striata and the RDN has a lateral asymmetry. The data are discussed with reference to histological observations suggesting a higher density of 5-hydroxyindole containing cell bodies in the lateral region than in the midline of this "unpaired" nucleus.