Study the Effect of Alpha $ Beta Adenergic Agonist and Antagonist on Fish Melanophores

Isolated scale melanophores of Rasbora elanga were examined for the effect of various specific and non-specific agonists and antagonists prepared in physiological Ringer solution. The responses were recorded as Melanophore Index Number. It was observed that adrenaline, nor adrenaline, phenylephrine and clonidine induced melanosome aggregation in a dose-depended manner. Yohimbine strongly inhibited the melanosome aggregatory effect of adrenaline and clonidine. Hence, it may be concluded that pigment aggregating adrenoceptors are both α1 and α2 types but the melanophore membrane in this fish is endowed with α2-adrenoceptors. The pigment dispersion on treatment with salbutamol and isoxsuprine, β2-agonists indicate the presence of β2-adrenoceptors on the melanophores of this species. Atropine, a muscarinic antagonist appears to act directly on the melanophores as its treatment caused rapid melanosome dispersion.