GLUTAMATERGIC AND CHOLINERGIC INPUTS FROM THE PEDUNCULOPONTINE TEGMENTAL NUCLEUS TO DOPAMINE NEURONS IN THE SUBSTANTIA-NIGRA PARS COMPACTA

Postsynaptic responses of dopamine (DA) neurons in the substantia nigr a pars compacta (SNc) to stimulation of the pedunculopontine tegmental nuclei (PPN) were studied in in vitro slice preparations in the rat. The recorded neurons were intracellularly injected with biocytin and a lso identified as DA neurons by an immunocytochemical technique. PPN s timulation induced in DA neurons monosynaptic excitatory postsynaptic potentials (EPSPs) that consisted of early transient and slow componen ts. An application of anti-glutamatergic agents (1 mM kynurenic acid a nd/or 30 mu M 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX)) in the bath ing media partially suppressed the EPSPs, indicating that PPN inputs t o SNc DA neurons are glutamatergic and non-glutamatergic. Anti-glutama tergic resistant EPSPs were suppressed by applications of anti-choline rgic agents such as atropine, mecamylamine, and pirenzepine. These dat a indicate a convergence of glutamatergic and cholinergic excitatory i nputs from the PPN to SNc DA neurons and that both nicotinic and musca rinic receptors are involved in the cholinergic transmission.