Serotonin and octopamine produce opposite postures in lobsters.

Serotonin and octopamine, injected into the circulation of freely moving lobsters and crayfish, produce opposite behavioral effects. Octopamine injection produces sustained extension of the limbs and abdomen; serotonin injection produces sustained flexion. Neurophysiological analyses show that these postures can be accounted for by opposing, coordinated effects of these amines on patterns of motoneuron activity recorded from the ventral nerve cord.