Abstract
It is well established that the mammalian caudate nucleus has both dopaminergic and cholinergic innervation (1, 2). The cell bodies of the dopaminergic neurons are found mainly in the pars compacta of the substantia nigra and appear to project mainly to the caudate nucleus and putamen (3). Unlike the dopaminergic neurons, some cholinergic fibers appear to exist as interneurons with both cell bodies and terminals present within this structure (4, 5). Recently it has been suggested that dopaminergic fibers make synapses with cell bodies of the cholinergic interneurons in the caudate nucleus (4, 6, 7). These studies have also suggested that dopamine exerts an inhibitory effect on cholinergic interneurons. For instance, blockade of dopaminergic transmission with neuroleptic drugs increases the turnover of acetylcholine in striatal neurons (6) and decreases striatal acetylcholine levels. This neuroleptic-induced increase of acetylcholine turnover can be prevented or reversed by dopamine receptor stimulating agents such as apomorphine or L-DOPA (6, 7) and these same agonists produce an increase striatal levels of acetylcholine (8).
The present studies were carried out to investigate whether or not exogenously administered dopamine could alter the release of acetylcholine induced by electrical stimulation of superfused slices of rat striatum. It was thought that this would provide information concerning the concept of inhibitory dopaminergic regulation of cholinergic neurotransmission in this structure.
Methods and materials. Rats were killed by decapitation and brains quickly removed and placed in the cold room at 4° where they were sliced with a MacIlwain tissue chopper at a thickness of 1 mm. Individual striatal slices of this thickness and approximately 3 cm in diameter were then separated from other brain regions. They were placed in 1.9 ml of Krebs-Ringer buffer at 37° for 10 min.
Get full access to this article
View all access options for this article.