The effects of castration and hormone replacement on runway behaviour and GABA concentrations in the septum.

The correlation between changes in the concentration of brain biogenic amines and behaviour was assessed in groups of rats tested in a straight alleyway under food-rewarded conditions. Prior to behavioural assessment male rats were castrated, sham-operated or castrated with testosterone substitution. Behaviourally, animals were tested under continuous reinforcement or extinction schedules prior to killing and neurochemical assessment. Although no overall change in behaviour was found with castration, castrates showed a greater variability in day-to-day performance. Septal concentration of γ-aminobutyric acid (GABA) were decreased in the continuously-reinforced castrated group. Treatment of castrated rats with testosterone reversed this change in the septal concentration of GABA, and also showed a more stable runway performance. The variability in behaviour is considered in relation to the septal function.