Localization of tyrosine hydroxylase-immunoreactive neurons in the cat hypothalamus, with special reference to fluorescence histochemistry.

The present study examines the distribution and morphological characteristics of neurons containing immunoreactivity of tyrosine hydroxylase in the cat hypothalamus. We used the indirect immunoperoxidase technique on vibratome sections. Tyrosine hydroxylase-immunoreactive cell bodies were widely distributed in discrete regions of the cat hypothalamus. Several principal cell groups were identified. They were seen in the posterior and dorsal hypothalamic areas, zona incerta, dorsomedial and lateral hypothalamic areas, arcuate nucleus, periventricular nucleus, paraventricular nucleus, and an area of the tuber cinereum and preoptic area. These cells presented two different morphological characteristics; small with two to three short processes and medium to large, multipolar with three to five long dendritic trees. The atlas is presented in twelve cross-sectional drawings of the cat hypothalamus from the level A8.5 to A15 of the Horsley-Clarke stereotaxic planes. We also examined the distribution of hypothalamic catecholamine fluorescent neurons by using the aqueous aldehyde method in combination with glyoxylic acid applied to vibratome sectioned tissues, which improves sensitivity. Comments are made on the relative localizations of the tyrosine hydroxylase-immunoreactive and aldehyde-induced histofluorescent cells, as well as on species differences between the cat, rat, and mouse.