Colour changes in cephalopods after neurotransmitter injection into the cephalic aorta

A method by which small quantities (1–10 μg) of neurotransmitters can be injected into the blood supplying the brain of cephalopods has been used to produce conspicuous and instantaneous colour changes in the skin of the arms, head and body. Of the transmitter substances known to be present in the cephalopod brain, dopamine, noradrenalin and octopamine cause darkening when injected, acetylcholine causes paling and 5- hydroxytryptamine elicits a mottled patterning. Other evidence is presented that these substances are acting centrally to produce these effects, and the findings are related to the known organization of the lobes in the c. n. s. controlling the chromatophores.