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.