MODULATION OF DOPAMINE EFFLUX IN THE NUCLEUS-ACCUMBENS AFTER CHOLINERGIC STIMULATION OF THE VENTRAL TEGMENTAL AREA IN INTACT, PEDUNCULOPONTINE TEGMENTAL NUCLEUS-LESIONED, AND LATERODORSAL TEGMENTAL NUCLEUS-LESIONED RATS

Microinjections of the cholinergic receptor agonist nicotine and the c holinesterase inhibitor neostigmine were made into the ventral tegment al area (VTA) of urethane-anesthetized rats, and dopamine (DA) efflux in the nucleus accumbens was measured using in vivo chronoamperometry. Dose-dependent increases in the chronoamperometric signals correspond ing to increased DA efflux were observed in the nucleus accumbens of n ormal intact rats after cholinergic stimulation of the VTA. The source of the cholinergic input to the VTA was investigated by making excito toxic lesions in either the laterodorsal tegmental nucleus (LDTg) or t he pedunculopontine tegmental nucleus (PPTg). Compared with sham-opera ted control animals, which showed the same response as intact, nonlesi oned rats, ibotenate lesions of the LDTg attenuated the stimulatory ef fects of intra-VTA neostigmine on DA efflux in the nucleus accumbens. In contrast, rats with ibotenate lesions of the PPTg showed normal nuc leus accumbens DA efflux after intra-VTA injections of neostigmine. Su ch lesions in the PPTg attenuate DA efflux in the caudate-putamen stim ulated by injections of neostigmine into the substantia nigra pars com pacta (SNc). The present data show that cholinergic neurons in the LDT g, but not the PPTg, regulate the activity of DA-containing neurons in the VTA, which complements previous data showing that cholinergic neu rons in the PPTg regulate DA-containing neurons in the SNc.