Influence of environment on GABA receptors in muricidal rats.

The influence of environment (isolation) on GABA receptor numbers ( [3H]-muscimol binding sites) and affinities was investigated in specific limbic areas known to be involved with the development of muricide. Olfactory bulbs of isolated rats were found to have identical numbers of [3H]-muscimol binding sites whether or not they were muricidal. However, in the olfactory bulbs of the aggregated animals a greater than two-fold increase was found in numbers of [3H]-muscimol binding sites in those rats that were muricidal. In the amygdala muricidal rats had a 32-34% increase in [3H]-muscimol binding sites over non-muricidal rats regardless of environment. In the septum non-muricidal rats had fewer [3H]-muscimol binding sites than muricidal rats and although the trend was evident, statistical vigor was seen only in the aggregated animals. Neither muricide nor isolation significantly influenced [3H]-muscimol binding numbers in the hypothalamus. GABA Ki values were examined in all brain regions and found to be the same in the isolated and aggregated animals whether or not they were muricidal. We concluded that environment appears to influence apparent GABA receptor numbers in the olfactory bulbs and septum whereas muricidal behavior correlates well with an increase in apparent number of GABA receptors in the amygdala. GABA receptors in the hypothalamus were not influenced by either environment or aggression.