Dopamine- and dopa-immunoreactive neurons in the cat forebrain with reference to tyrosine hydroxylase-immunohistochemistry.

The distribution of cell bodies containing immunoreactivities to dopamine (DA), L-3,4-dihydroxyphenylalanine (DOPA) and tyrosine hydroxylase (TH) was studied immunohistochemically in the cat forebrain especially in the hypothalamus with or without intraventricular administration of colchicine. In normal cats, DA-immunoreactive (IR) neurons, whose intensity of immunostainings was variable from one to another, were localized exclusively in the hypothalamus and showed a distribution pattern similar to that of TH-IR ones. They were distributed in the posterior, dorsal and periventricular hypothalamic areas. Arcuate cells showed no or very weak DA-immunoreactivity. Weak to intense DOPA-IR cells were distributed in a similar manner to DA-IR ones but were far smaller in number. In colchicine-treated animals, DA- and DOPA-immunoreactivities were enhanced particularly in arcuate and dorsal hypothalamic cells. A cluster composed of small DA- and DOPA-IR cells was identified in the area ventral to the mamillothalamic tract equivalent to rat A13c TH-IR cell group. Colchicine treatment enabled us to visualize a large number of TH-IR perikarya in the medial and lateral preoptic areas, anterior commissure nucleus, basal forebrain, area closely related to the organum vasculosum laminae terminalis, and some in the bed nucleus of the stria terminalis as has been reported in other species. However, virtually none of these cells contained detectable DA- and DOPA-immunoreactivities.