Voluntary ethanol intake increases extracellular acetylcholine levels in the ventral tegmental area in the rat.
OBJECTIVE
Concurrent use of ethanol and nicotine (tobacco) is often seen in human beings. In previous animal experiments, we have demonstrated that nicotinic acetylcholine receptors, especially alpha-conotoxin MII and mecamylamine sensitive receptors located in the ventral tegmental area may be involved in the stimulatory, dopamine enhancing, and rewarding effects of ethanol in rodents. Ethanol may exert these effects via direct interaction with nicotinic acetylcholine receptors and/or indirectly via enhancement of extracellular acetylcholine levels in the ventral tegmental area. The present experiments investigated a possible indirect effect of ethanol in stimulating the mesoaccumbal dopamine system.


METHODS
Neurochemical effects of voluntary ethanol intake on extracellular ventral tegmental acetylcholine and accumbal dopamine levels were measured by means of in vivo microdialysis with a two-probe approach in freely moving rats.


RESULTS
Obtained data indicate that voluntary ethanol intake ( approximately 0.7 g/kg/h) leads to an increase of extracellular acetylcholine levels in the ventral tegmental area, and an almost time-locked increase of dopamine levels in the nucleus accumbens. A positive correlation between the ventral tegmental acetylcholine levels and ethanol intake as well as preference was also observed.


CONCLUSIONS
The present results suggest that voluntary ethanol intake enhances extracellular ventral tegmental acetylcholine that may interact with nicotinic acetylcholine receptors, possibly alpha-conotoxin MII sensitive receptors, localized in the ventral tegmental area that subsequently may stimulate dopamine overflow in the nucleus accumbens.
Larsson
Anna
A
Institute of Physiology and Pharmacology, Department of Pharmacology, The Sahlgrenska Academy, Göteborg University, Box 431, SE-405 30 Göteborg, Sweden.
Edström
Lena
L
Svensson
Lennart
L
Söderpalm
Bo
B
Engel
Jörgen A
JA
D000109:Acetylcholine / Q000378:metabolism*; D000428:Alcohol Drinking / Q000503:physiopathology*; D000818:Animals; D004298:Dopamine / Q000378:metabolism; D045604:Extracellular Fluid / Q000378:metabolism*; D008297:Male; D009714:Nucleus Accumbens / Q000503:physiopathology; D051381:Rats; D017208:Rats, Wistar; D013223:Statistics as Topic; D017557:Ventral Tegmental Area / Q000503:physiopathology*
D000109:Acetylcholine; D004298:Dopamine