Effect of adrenergic receptors in melanophores of teleosts fish: Rasbora elanga

Abstract

In the melanophores on isolated scale preparation of fish Rasbora elanga, adrenaline a non-selective adrenergic agonist produced dose dependent aggregation of melanosomes. The melanosome aggregation response of the amine was completely blocked by Yohimbine (10-5 M), but propranolol (10-5 M) a non-selective β- antagonist failed in blocking such a response of amine, where it produced its normal response. The results presented suggest that the melanosome aggregation in melanophores of the fish can be mediated by α 2 adrenergic receptors. These receptors are known to couple with Gi proteins that utilize the enzyme adenylate cyclase to decrease the intracellular concentration of cAMP resulting in retrograde transport of melanosomes to be accumulated at the cell centre. β-receptors have also been implicated to mediate melanosome dispersion by stimulating Gs protein in various fish species.