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

In previous studies we have shown that sodium cyanide decreases the striatal dopamine levels within 60s compared with the controls. Treatment with sodium cyanide also increases the naturally occuring 3,4-dihydroxy-L-phenylalanine (L-DOPA) in the striatum, but not in any other region studied. An increase in the in vivo synthesis of dopamine in cyanide-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 binding 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 receptor binding was decreased only at 1 h after the cyanide administration. Neither sodium cyanide nor its metabolite sodium thiocyanate did significantly change the striatal dopamine D-1 and D-2 receptor binding in vitro. Accordingly sodium cyanide and sodium thiocyanate do not have direct effects on the dopamine receptors studied. The effects of cyanide on dopamine D-1 and D-2 receptors are probably in part due to the effect of cyanide on the release of dopamine.