Inhibition by gamma-hydroxybutyrate of chlorpromazine-induced increase in homovanillic acid.

1. gamma-Hydroxybutyrate and its lactone precursor, gamma-butyrolactone, when administered in anaesthetic doses block the increase in the cerebral concentration of homovanillic acid normally observed after administration of chlorpromazine or haloperidol.2. Other hypnotics such as glutethimide, urethane, chloralose, chloral hydrate and thiopentone do not have this ability even when administered in anaesthetic doses.3. The ability of gamma-hydroxybutyrate to block the neuroleptic-induced increase in cerebral homovanillic acid is not due to a reduction in body temperature since a similar effect is observed in rats treated under conditions (32 degrees C) in which body temperature remains normal.4. Possible mechanisms for this action of gamma-hydroxybutyrate are discussed.