Different levels of gamma-synuclein mRNA in the cerebral cortex of dominant, neutral and submissive rats selected in the competition test.

Synucleins are small proteins regulating the filamentous network that in turn influences the release of dopamine and glutamate neurotransmitters involved in mood and motivation processes. We have studied the pattern of synuclein expression in animal models for mania and depression. Dominant behavior, as defined in a food competition test with dyads of rats, can serve as a model of mania and submissive behavior as a model of depression. The expression of alpha-, beta- and gamma-synuclein was analyzed in four regions of cortex from dominant, neutral and submissive rats using TaqMan reverse transcription-polymerase chain reaction technology. The expression levels of gamma-synuclein were elevated consistently in all regions of cerebral cortex of dominant rats (P <0.05; 23.5 +/- 1.1, normalized units) in contrast to the submissive rat group (10.3 +/- 1.2). Neutral rats had intermediate cerebral cortex levels of gamma-synuclein expression (15.7 +/- 1.4) that were significantly lower than that in dominant rats (P <0.05). No changes in alpha- or beta-synuclein expression were observed among the groups. These studies indicate that gamma-synuclein levels in the cerebral cortex were differentially associated with dominant and submissive behavior.