Differential presynaptic effects of hexachlorocyclohexane isomers on noradrenaline release in cerebral cortex

To investigate presynaptic effects of hexachlorocyclohexane (HCH) isomers, the release of noradrenaline (NA) in brain tissue was analyzed using rat cerebral cortical slices preloaded with [3H]-NA. γ-HCH (lindane) 50 μM significantly enhanced the [3H]-NA release evoked by 15-25 mM K+. α- and β-HCH did not produce any significant effect on K+-evoked [3H]-NA release. δ-HCH induced a significant decrease of the 25 mM K+-evoked release of [3H]-NA. The effect of the γ- and δ-HCH isomers on the presynaptic action of the α2-agonist clonidine and the α2-antagonist yohimbine was also studied. The presynaptic inhibitory effect of clonidine and the stimulatory effect of yohimbine on [3H]-NA release was attenuated by lindane and δ-HCH, respectively. These results are consistent with a presynaptic action of the HCH isomers on noradrenergic release processes