ABSTRACT
Effects of GABA-ergic agonists and antagonists were examined on the melanophores of a carp C. mrigala in vitro. GABA and baclofen both induced concentration - related dispersion in fish melanophores. Denervation of the melanophores by reserpine treatment potentiated the sensitivity of the melanophores to GABA. While denervation by cooling treatment inhibited the sensitivity of the melanophores to GABA, atropine, bicuculline and pentylenetetrazole all inhibited the dispersal responses of the melanophores induced by higher concentrations of GABA. 5-aminovaleric acid also significantly inhibited the dispersion of the melanophores induced either by GABA or baclofen. It is concluded that GABA-ergic agonist induced dispersal responses in C mrigala melanophores are mediated through specific GABA receptors. The presence of both GABAA and GABAB receptors in this fish melanophores has been indicated.