Study of the effects of the casein derived bitter tastant on the melanophores in milieu with the melatonin receptors

Abstract

The present study was undertaken to ascertain whether the casein derived bitter tastant Cyclo (Leu-Trp) [CLT] has an affinity or not for the particular receptors of the pineal hormone, melatonin, on the melanophores of a major carp Labeo rohita (Ham.). The bitter tastant CLT, in the dose range of 3.34 × 10⁻¹⁶ M to 3.34 × 10⁻⁴ M, has induced an aggregatory effect but not in a dose dependent manner. Binding of CLT with the receptors may vary at different concentrations. Denervation of the melanophores has shown a complete inhibition of the CLT mediated aggregation. Prazosin has partially inhibited the aggregatory effect of CLT. Moreover, the bitter tastant’s response is mediated through the α₂ adrenoceptors only at particular dose ranges. The MT₁ and MT₂ melatonin receptor antagonist luzindole and the MT₂ specific antagonist K185 have perfectly blocked the aggregatory effects of CLT. We have found that the CLT mediated aggregatory effect is dependent upon the release of neurotransmitters and the two subtypes of melatonin (MT) receptors (MT₁ and MT₂) possess a perfect affinity towards the bitter tastant CLT. Our study demands a need to further make a clinical research on the effects of bitter tastants on the physiology of the biological rhythm maintaining hormone melatonin.

Keywords::

• Denervation
• K185
• luzindole
• melanophores
• melatonin
• prazosin
• yohimbine

Acknowledgement

We are thankful to the Bachem at Bubendorf (Switzerland) for the free gift of the drug cyclo (Leu-Trp).

Declaration of interest

The authors report no declarations of interest.