Effects of two isomers of hexachlorocyclohexane (HCH) on cortical beta-adrenoceptors in rat brain.

Two isomers of hexachlorocyclohexane (HCH) have profound effects on the acquisition of kindled seizures. The gamma-isomer (lindane, gamma-HCH) increases the rate of acquisition in a dose-related manner whereas the beta-isomer (beta-HCH) has the opposite effect, retarding the rate in a dose-related manner. There is evidence that adrenergic influences may play a role in seizure generalization and in this study we examined the effect of these two isomers of HCH on the binding of a ligand to beta-adrenoceptors. Tritiated dihydroalprenolol was used as the ligand in an assay using cortical tissue from rats after 10 days of treatment with 10 mg/kg, p.o. of isomers or corn oil. Results showed a statistically significant decrease in the number of beta-adrenoceptors in cortical tissue taken from gamma-HCH-treated rats. In contrast, there was a statistically significant increase in the number of beta-adrenoceptors cortical tissue taken from beta-HCH-treated rats. Neither treatment produced a significant change in KD. We concluded that the beta-adrenoceptor system in rat cortex is differentially affected by the isomers of HCH. Because the kindling model of epilepsy is sensitive to modulations in adrenergic function, this system may be involved in the pro- and anticonvulsant effects of these HCH isomers on kindling acquisition.