Striatal dopaminergic D1 and D2 receptors after intracerebroventricular application of alloxan and streptozocin in rat.

Intracerebroventricular application of low, nondiabetogenic doses (500 micrograms kg-1) of alloxan and streptozocin is followed by alterations of the dopaminergic system in rat striatum. In this brain region the dopamine content significantly increased, while the density of dopaminergic D1 receptors significantly decreased seven days after the intracerebroventricular application of betacytotoxics, as compared with the control group. The density of dopaminergic D2 receptors in striatum remained unchanged. Dopaminergic D1 and D2 receptors operate through signalling mechanism of G proteins, but no changes of Gs and Gi proteins content have been found in rat striatum after the intracerebroventricular application of betacytotoxics. As intracerebroventricular, nondiabetogenic administration of betacytotoxics produces changes of the striatal dopamine content and D1 receptor density similar to that produced by peripheral, diabetogenic administration of these drugs, the effect might be related not solely to pancreatic beta cells damage, but to alterations of the brain insulin system, as well.