The effects of neurotensin on GABA and acetylcholine release in the dorsal striatum of the rat: an in vivo microdialysis study.

The effects of local perfusion with the tridecapeptide neurotensin (NT) on endogenous gamma-aminobutyric acid (GABA), acetylcholine (ACh) and choline release in the dorsal neostriatum were monitored using in vivo microdialysis in the halothane anaesthetized rat. The results show that NT (10 and 1000 nM) differentially regulates striatal GABA release without significantly influencing the release of either striatal ACh or choline. NT increased striatal GABA release both in the absence and presence of the ACh esterase inhibitor neostigmine (neo; 10 microM) in the perfusion medium. However, both basal GABA levels and responsitivity to NT were elevated in the presence of neo. The NT induced increase in striatal GABA release was reversed by the addition of tetrodotoxin (TTX; 1 micron) to the perfusion medium. These data suggest that (1) NT may play a role in modulating GABAergic neurotransmission in the dorsal neostriatum and (2) that the increase in GABA release may occur independently of an increase in the cholinergic component in the dorsal neostriatum, possibly via high affinity NT receptors located on striatal GABAergic neurons.