Effect of gamma-hexachlorocyclohexane and its isomers on proto-oncogene c-fos expression in brain.

By means of in situ hybridization, the induction of proto-oncogene c-fos in rat brain after administration of several convulsants has been studied. The organochlorine insecticide gamma-hexachlorocyclohexane (lindane) has been shown to induce c-fos expression in a dose dependent manner. 30 mg/kg of lindane increased c-fos expression in cortical and hippocampal areas. The two non convulsant isomers of lindane, alpha- and delta-HCH, were not able to induce the expression of the proto-oncogene, but blocked that elicited by lindane. Pentylenetetrazole (PTZ) and picrotoxin (PTX), a known GABAA-receptor antagonist, have also been considered. Both of them were able to induce c-fos, although the pattern of expression was not the same in each case. alpha- and delta-HCH, were administered prior to the mentioned toxicants, affecting the proto-oncogene expression in different ways. We propose here that the distribution of c-fos mRNA after different treatments can be used as a marker of neurotoxic action.