Distribution of dopamine-immunoreactive cell bodies in the guinea-pig brain

The distribution of dopamine (DA)-containing neurons in the guinea-pig brain was investigated immunohistochemically using antibodies raised against glutaraldehyde-conjugated DA. Light microscopical studies revealed the presence of nearly 50,000 DA-immunoreactive cells, localized throughout the hypothalamus and the midbrain. With a few exceptions the dopaminergic cell groups identified by different (immuno)histochemical techniques in the rat were also demonstrated in the guinea-pig brain. These include tyrosine hydroxylase-immunoreactive positive, dopamine-beta-hydroxylase-immunoreactive negative cells in the medial hypothalamus, the ventral tegmental area, the substantia nigra and the dorsal raphe nucleus. A group of dopaminergic cell bodies, not present in the rat, was found to extend from the nucleus retrochiasmaticus into the rostral part of the eminentia mediana. Also at variance with the rat, the guinea-pig lacked DA-immunoreactive cells in a number of homologous areas corresponding to the A15- and A8 cell groups and partly, the A14- and A10 cell groups. However, in general, the localization of dopaminergic cell bodies in the guinea-pig brain appeared similar to that in the rat brain.