Galanin microinjection in the third ventricle increases voluntary ethanol intake.
BACKGROUND
The neuropeptide galanin increases food intake. Chronic ethanol (EtOH) increases the expression of galanin in the hypothalamus. The research presented here examines the effects of microinjection of galanin in the third ventricle on voluntary alcohol intake.


METHODS
Male Sprague Dawley rats with a cannula in the third ventricle were given access to increasing concentrations of EtOH for 12 hr/day until all acquired a preference for 7% EtOH over water in a two-bottle choice. Rats then received a microinjection of galanin (0, 1, and 3 nmol) alone or in combination with the galanin antagonist M40 (1 nmol) and with M40 alone to determine the effects on EtOH and water intake. Tests were conducted during both the light and dark periods of a 12:12-hr light-dark cycle with food available ad libitum. As a control for galanin-induced calorie intake, both EtOH and food were measured in a subset of rats during the dark.


RESULTS
Microinjections of galanin (1.0 and 3.0 nmol) increased EtOH consumption during both periods of the light-dark cycle. Galanin's effect on ethanol intake during the light was large relative to the very low intake of food and water during this period. Rats increased their intake of EtOH but not food. Receptor specificity for galanin (3 nmol) was shown by the galanin antagonist M40, which blocked the increase in EtOH intake. M40 alone decreased EtOH intake slightly.


CONCLUSIONS
These data show that galanin injected in the third ventricle increases EtOH consumption and that the effect can occur during both the light and the dark periods of the diurnal cycle in the presence of food and water. This suggests that galanin may play a role in augmenting voluntary alcohol intake and perhaps the development of alcohol dependence.
Lewis
Michael J
MJ
Department of Psychology, Princeton University, Princeton, NJ 08544, USA. mlewis@princeton.edu
Johnson
Deanne F
DF
Waldman
Daniel
D
Leibowitz
Sarah F
SF
Hoebel
Bartley G
BG
D000428:Alcohol Drinking / Q000378:metabolism; D000818:Animals; D004305:Dose-Response Relationship, Drug; D004326:Drinking / Q000187:drug effects / Q000502:physiology; D004435:Eating / Q000187:drug effects / Q000502:physiology; D000431:Ethanol / Q000008:administration & dosage*; D019004:Galanin / Q000008:administration & dosage*; D007276:Injections, Intraventricular; D008297:Male; D008845:Microinjections / Q000379:methods*; D051381:Rats; D017207:Rats, Sprague-Dawley; D020542:Third Ventricle / Q000187:drug effects* / Q000502:physiology
D000431:Ethanol; D019004:Galanin