Anatomical localization in hippocampus of tetrahydro-beta-carboline-induced alcohol drinking in the rat

Guide cannulae for unilateral or bilateral micro-injection were implanted stereotaxically into the dorsal hippocampus of the male adult Sprague-Dawley rat. Following post-operative recovery, the animal's individual preference for ethyl alcohol in concentrations from 3-30% (v/v) was tested over a 9-day period by a three-bottle, two-choice technique. Following this pre-screen, 3.0 microliter of 1,2,3,4-tetrahydro-beta-carboline (TH beta C) hydrochloride, a benzodiazepine receptor antagonist, was infused in a concentration of 25-200 ng into the hippocampus of each unrestrained rat twice a day for three to six days. After the first two days of infusion, the 9-day preference test for alcohol drinking was begun and continued identically as in the earlier test. A third alcohol preference test during which no injections were given was conducted at an interval of two weeks following the second. The micro-injection of TH beta C into certain sites in the hippocampus enhanced alcohol consumption from 0.5-2.0 g/kg during the 9-day test interval. The magnitude of this elevated intake was dependent on the site of infusion and was more pronounced when intermediate concentrations of 7-12% alcohol were offered to the rat. At sites in coronal planes encompassing AP 3.0 and AP 3.5, the micro-injection of TH beta C enhanced alcohol drinking significantly in 75% of the animals; however, when delivered at sites in coronal planes AP 1.0 through AP 2.5, TH beta C augmented alcohol drinking significantly in 15% of the rats.(ABSTRACT TRUNCATED AT 250 WORDS)