SYMMETRICAL GENERALIZATION BETWEEN THE DISCRIMINATIVE STIMULUS EFFECTS OF GAMMA-HYDROXYBUTYRIC ACID AND ETHANOL - OCCURRENCE WITHIN NARROW DOSE RANGES

Gamma-hydroxybutyric acid (GHB) has been shown to reduce ethanol consu mption and suppress ethanol withdrawal syndrome both in laboratory ani mals and humans. The present study was designed to assess the similari ty between the discriminative stimulus effects, or subjective feelings , of GHB and ethanol using a T-maze, food-reinforced drug discriminati on procedure. Three groups of rats were trained to discriminate ethano l (1.0 or 2.0 g/kg; p.o.) or GHB (300 mg/kg; p.o.) from water. In the 1.0 g/kg ethanol-trained rats, substitution for ethanol was an inverte d U-shape function of GHB dose, with only 300 mg/kg GHB resulting in c omplete substitution for ethanol. No dose of GHB elicited selection of ethanol-appropriate arm higher than 10% in the 2.0 g/kg ethanol-train ed group. In the 300 mg/kg GHB-trained rats, complete substitution for GHB occurred only at the dose of 1.0 g/kg ethanol. Doses of ethanol l ower or higher than 1.0 g/kg did not substitute for GHB. The results o f the present study indicate that symmetrical generalization between e thanol and GHB occurred within narrow dose ranges. They are discussed in terms of common neurotransmitter systems involved in the mediation of GHB and ethanol effects.