Behavioral depression after intraventricular infusion of octopamine in rats.

The behavioral and neurochemical effects of four intraventricular infusions of octopamine (3,200 micrograms), tryptophan (800 micrograms), and octopamine plus tryptophan delivered over 6 hours was studied in rats after performing a portacaval anastomosis or a sham operation. After each infusion, each animal was rated for neurologic depression with a 17 point test battery. Although overt coma was not induced, octopamine infusions severely depressed neurologic function. Concentrations of norepinephrine, dopamine, and serotonin in the brain were significantly decreased after the infusion of octopamine. Levels of norepinephrine in the brain were significantly correlated with neurologic status and greater depletion of norepinephrine was associated with greater neurologic depression. These studies demonstrate that infusing large amounts of the trace amine octopamine depresses behavior in the rat and this depression is most closely associated with depletion of stores of norepinephrine in the brain.