DISTRIBUTION OF CATECHOLAMINERGIC EFFERENT FIBERS IN THE RAT GLOBUS-PALLIDUS AND THEIR RELATIONS WITH CHOLINERGIC NEURONS

The topographical distribution of catecholaminergic nerve fibres and t heir anatomical relationship to cholinergic elements in the rat globus pallidus were studied. Peroxidase-antiperoxidase and two-colour immun operoxidase staining procedures were used to demonstrate tyrosine hydr oxylase (TH), dopamine beta-hydroxylase (DBH), phenylethanolamine N-me thyltransferase (PNMT) and choline acetyltransferase (ChAT) immunoreac tivities, combined with acetylcholinesterase (AChE) pharmacohistochemi stry. TH immunoreactive nerve fibres were seen to enter the globus pal lidus from the medial forebrain bundle. The greatest density of such f ibres was found in the ventral region of the globus pallidus, which wa s also characterized by the greatest density of ChAT immunoreactive ne urons. TH immunoreactive nerve fibres showed varicose arborizations an d sparse boutons, which were occasionally seen in close opposition to cholinergic structures. In all regions of the globus pallidus, there w ere also larger, smooth TH immunoreactive nerve fibres of passage to t he caudate putamen. A smaller number of DBH immunoreactive nerve fibre s and terminal arborizations were found in the substantia innominata, internal capsule and in the globus pallidus bordering these structures . A few PNMT immunoreactive nerve fibres in the substantia innominata and internal capsule did not enter the globus pallidus. Electron micro scopy revealed TH immunoreactive synaptic profiles in the ventromedial area of the globus pallidus corresponding to the nucleus basalis magn ocellularis of Meynert (nBM). These made mainly symmetrical and only a few asymmetrical synaptic contacts with dendrites containing AChE rea ction product. The results indicate that cholinergic structures in the nBM are innervated by dopaminergic fibres and terminals, with only a very small input from noradrenergic fibres. (C) 1998 Elsevier Science B.V. All rights reserved.