Nicotine releases stereoselectively and Ca-dependently endogenous 3,4-dihydroxyphenylalanine from rat striatal slices

In superfused slices of rat striatum, nicotine-evoked release of endogenous 3,4-dihydroxyphenylalanine (DOPA) was studied in comparison with that of dopamine (DA). (if(±)-Nicotine (0.1–10 μM) constantly and repetitively released DOPA and DA over a similar time course in a concentration-dependent manner. The ratio of DOPA and DA evoked was approximately 1:2–3. The turnover rate of DOPA was about 300 times higher compared to DA. (±)-Nicotine (10 μM)-induced DOPA release was mecamylamine (20 μM)-sensitive, Ca²⁺-dependent and tetrodotoxin (0.3 μM)-insensitive. The (+)-isomer induced no DOPA release. These characteristics of DOPA release were almost the same as those of DA. Nicotine evokes endogenous DOPA via nicotinic cholinergic receptors in a manner similar to the transmitter DA. These findings further support a probable role of DOPA as a neuroactive substance in the rat central nervous system.