TETRODOTOXIN-SENSITIVITY OF NICOTINE-EVOKED DOPAMINE RELEASE FROM RATSTRIATUM

Recent observations from synaptosome preparations have questioned the tetrodotoxin (TTX) insensitivity of nicotine-evoked dopamine release i n the striatum, a characteristic previously considered diagnostic of p resynaptically located nicotinic acetylcholine receptors (nAChRs). The refore, we have undertaken a comparison of nicotine-evoked dopamine re lease in the presence of TTX from the rat striatum in vitro, using syn aptosomes and brain slices, and in vivo, using microdialysis. In P2 an d Percoll-purified synaptosome preparations, 1.5 mu M TTX partially in hibited nicotine-evoked [H-3]dopamine release by 54% and 37%, respecti vely, whereas in more intact preparations (brain slices and microdialy sis) TTX completely inhibited mecamylamine-sensitive nicotine-stimulat ed dopamine release. These results suggest that caution should be exer cised in the interpretation of TTX sensitivity of nicotine-evoked resp onses with regard to the location of nAChRs. Copyright (C) 1996 Elsevi er Science Ltd.