Content area
Abstract
5-Hydroxytryptamine^sub 2A^ (5-HT^sub 2A^) receptor kinetics was studied in cerebral cortex and brain stem of streptozotocin (STZ) induced diabetic rats. Scatchard analysis with [^sup 3^H] (±) 2,3dimethoxyphenyl-1-[2-(4-piperidine)-methanol] ([^sup 3^H]MDL100907) in cerebral cortex showed no significant change in maximal binding (B^sub max^) in diabetic rats compared to controls. Dissociation constant (K^sub d^) of diabetic rats showed a significant decrease (p < 0.05) in cerebral cortex, which was reversed to normal by insulin treatment. Competition studies of [^sup 3^H]MDL100907 binding in cerebral cortex with ketanserin showed the appearance of an additional low affinity site for 5-HT^sub 2A^ receptors in diabetic state, which was reversed to control pattern by insulin treatment. In brain stem, scatchard analysis showed a significant increase (p < 0.05) in B^sub max^ accompanied by a significant increase (p < 0.05) in K^sub d^. Competition analysis in brain stem also showed a shift in affinity towards a low affinity State for 5-HT^sub 2A^ receptors. All these parameters were reversed to control level by insulin treatment. These results show that in cerebral cortex there is an increase in affinity of 5-HT^sub 2A^ receptors without any change in its number and in the case of brain stem there is an increase in number of 5HT^sub 2A^ receptors accompanied by a decrease in its affinity during diabetes. Thus, from the results we suggest that the increase in affinity of 5-HT^sub 2A^ receptors in cerebral cortex and upregulation of 5-HT^sub 2A^ receptors in brain stem may lead to altered neuronal function in diabetes.[PUBLICATION ABSTRACT]