Abnormal c-fos expression in the lateral habenula during dystonic attacks in a hamster model of idiopathic dystonia

The genetically dystonic hamster (dtsz), an animal model of idiopathic dystonia, displays sustained twisting movements and postures either spontaneously or in response to mild stress. In the present study the expression of c-fos immunoreactive neurons (Fos-ir), used as an indicator of neuronal activity, was investigated within various brain regions in dtsz hamsters and non-dystonic control hamsters. Under baseline condition, i.e. in the absence of dystonia, the expression of Fos-ir did not reveal any differences between dtsz hamsters and controls. However, in response to mild stress several brain regions, particularly the lateral habenula (LHb), exhibited differences in c-fos induction in dtsz hamsters and controls. Whereas in the LHb the expression of Fos-ir was markedly enhanced in controls, it showed almost no increase in dystonic hamsters, indicating impaired neuronal activity. Since the lateral habenula receives major input from the basal ganglia via the entopeduncular nucleus, the present data might indicate that basal ganglia are involved in the dystonic syndrome in mutant hamsters.