Effects of cerebral lesions on binding sites for calcitonin and calcitonin gene-related peptide in the rat nucleus accumbens and ventral tegmental area.

Binding site densities of 125I]-labelled salmon calcitonin and human calcitonin gene-related peptide were investigated in the rat nucleus accumbens and ventral tegmental area by means of quantitative autoradiography following selective brain lesions. 125I]salmon calcitonin and 125I]human calcitonin gene-related peptide binding sites were highly concentrated in the accumbens, whereas the ventral tegmental area only contained 125I]salmon calcitonin binding sites. Unilateral injection of 6-hydroxydopamine into the ventral tegmental area did not alter 125I]salmon calcitonin and 125I]human calcitonin gene-related peptide binding site densities in the ipsilateral accumbens, while it produced a significant decrease in 125I]salmon calcitonin binding sites in the lesioned ventral tegmental area (-50%). In contrast, following unilateral injection of quinolinic acid into the accumbens, the densities of 125I]salmon calcitonin and 125I]human calcitonin gene-related peptide binding sites were significantly decreased in the lesioned accumbens (-57% and -56%, respectively), while 125I]salmon calcitonin binding site densities were not modified in the ipsilateral ventral tegmental area. The present study clearly suggests that 125I]salmon calcitonin and 125I]human calcitonin gene-related peptide binding sites are located on intrinsic neurons but not on the dopaminergic nerve terminals in the accumbens. Moreover, a certain proportion of 125I]salmon calcitonin binding sites could be present on dopaminergic cell bodies in the ventral tegmental area.