Site-Specific Microinjection of Baclofen Into the Anterior Ventral Tegmental Area Reduces Binge-Like Ethanol Intake in Male C57BL/6J Mice

The GABA(B) agonist baclofen has been shown to alter ethanol intake in human and animal studies (E. M. Moore et al., 2007). GABA(B) receptors are located within the ventral tegmental area (VTA: A. Imperato & G. DiChiara, 1986) and therefore may be involved in modulating Voluntary ethanol intake. The present study assessed the effects of baclofen in a variation on a new mouse model of binge-like ethanol intake that takes advantage of the nocturnal nature of this species (J. S. Rhodes, K. Best, J. K. Belknap, D. A. Finn, & J. C. Crabbe, 2005; J. S. Rhodes et al., 2007). Baclofen or saline was microinjected into the anterior or posterior VTA of male C57BL/6J mice. Immediately afterward, mice were presented with ethanol, water, or sugar water using the Drinking in the Dark model, a procedure of fluid administration for 2 hr, 3 hr into the dark cycle). Fluid intake was recorded at 30. 60, 90, and 120 min: retro-orbital sinus bloods were sampled upon termination of the 120-min ethanol access period. Baclofen reduced binge-like ethanol intake when microinjected into the anterior VTA, whereas posterior VTA microinjections did not alter ethanol intake. Baclofen had no effect on water or sugar water intake when administered to anterior or posterior VTA. These results add to the growing literature Suggesting that GABA(B) receptor systems are important in the modulation of binge-like ethanol intake and suggest that the GABA(B) receptor system may have different roles in anterior versus posterior VTA.