EFFECTS OF CYANIDE ON THE STRIATAL DOPAMINE-RECEPTOR BINDING IN THE RAT

In previous studies we have shown that sodium cyanide decreases the st riatal dopamine levels within 60s compared with the controls. Treatmen t with sodium cyanide also increases the naturally occuring 3,4-dihydr oxy-L-phenylalanine (L-DOPA) in the striatum, but not in any other reg ion studied. An increase in the in vivo synthesis of dopamine in cyani de-treated rats has also been observed. In order to further elucidate the effects on the central dopaminergic pathways the effects of sodium cyanide on the striatal dopamine D-1 and dopamine D-2 receptor bindin g were studied in vitro and after administration of sodium cyanide. In the rats injected with sodium cyanide (2.0 mg/kg, i.p.) the B-max of the striatal dopamine D-1 receptor binding was significantly decreased 15 min and 1 h after the treatment. The striatal dopamine D-2 recepto r binding was decreased only at 1 h after the cyanide administration. Neither sodium cyanide nor its metabolite sodium thiocyanate did signi ficantly change the striatal dopamine D-1 and D-2 receptor binding in vitro. Accordingly sodium cyanide and sodium thiocyanate do not have d irect effects on the dopamine receptors studied. The effects of cyanid e on dopamine D-1 and D-2 receptors are probably in part due to the ef fect of cyanide on the release of dopamine.