Catecholamine-containing nerve terminals in piloarrector muscles of stump-tailed macaques (Macaca arctoides) and the effects of local injection of 6-, and 5-hydroxydopamine.

The fluorescence histochemical method of Falck-Hillarp (62) demonstrates dense plexuses of catecholamine-containing nerves in the piloarrector muscles of adult stump-tailed macaques. When these muscle fibers are viewed under the electron microscope, most of the axon terminal profiles between them contain numerous dense-cored vesicles (adrenergic); the rest of the terminals contain mainly agranular vesicles (cholinergic). Intradermal injections of 6-hydroxydopamine (6-OHDA, 1 and 5 mg) or 5-hydroxydopamine (5-OHDA, 10mg) into the scalp caused the fluorescence from the nerve fibers in the muscles to completely disappear. The 6-OHDA injections induced severe degenerative changes in the adrenergic terminals whereas the 5-OHDA injections caused only the granules in the vesicles to increase in numbers. Thus, the piloarrector muscles of these macaques are innervated with both adrenergic and cholinergic terminals, but the former are more numerous than the latter.