Release of ATP from adrenergic nerves controlling pigment aggregation in tilapia melanophores

Using split fin preparations of a tilapia, Sarotherodon niloticus, release of ATP from the adrenergic melanosome-aggregating nerve was studied. Associated with the melanosome aggregation, an apparent release of ATP was detected following electrical nervous stimulation. ATP-release increased with increases in stimulus intensity. Spontaneous release of a small amount of ATP was also detected. It was concluded that ATP may be liberated as a co-transmitter along with the true one, norepinephrine, and it may function to help melanophores recover from the effect of the latter, thus enabling fish to change their hue very rapidly.