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Abstract:
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5-HT2A receptor binding parameters were studied in the cerebral cortex and brain stem of
control, diabetic, insulin, insulin + tryptophan and tr3yptophan treated streptozotocin diabetic
rats. Scatchard analysis using selective antagonist, [-H](±)2,3-dimethoxyphenyl-l-[2-(4-piperidine)-
methanol] ([3H]MDL100907) in cerebral cortex of diabetic rats showed a significant
decrease in dissociation constant (Kd) without any change in maximal binding (Bm). Competition
binding studies in cerebral cortex using ketanserin against [3H]MDL100907 showed
the appearance of an additional site in the low affinity region during diabetes. In the brain
stem, Scatchard analysis showed a significant increase in Bmax and Kd. Displacement studies
showed a shift in the receptor affinity towards a low affinity state. All these altered parameters
in diabetes were reversed to control level by insulin, insulin + tryptophan and tryptophan
treatments. Tryptophan treatment is suggested to reverse the altered 5-HT2Abinding and
blood glucose level to control status by increasing the brain 5-HT content. |