A stimulatory effect of intraaccumbens injections of noradrenaline on the behavior of rats in the forced swim test.

Intraaccumbens injections of catecholamines noradrenaline and dopamine, though not of serotonin, stimulated locomotion by rats in an open field, 10-15 min later. Similar effects were observed 5 min after microinjection of apomorphine whereas clonidine only attenuated locomotor activity. On the other hand, intraaccumbens administration of phenylephrine, isoproterenol and quipazine, in doses similar to an effective dose of noradrenaline, did not alter rat open field behavior. The escape-directed activity of rats in the forced swim test (FST) was stimulated 5 min after local administration of noradrenaline, phenylephrine, isoproterenol or apomorphine only. No effects in the FST were observed 15 min after noradrenaline injection or after intracaudate noradrenaline administration. The stimulatory effects of intraaccumbens noradrenaline injection in the FST were antagonized by the local pretreatment of rats with phentolamine, though not with propranolol. Accordingly, it is possible to conclude that both catecholamines, but not serotonin, play complex and probably distinct roles within the nucleus accumbens in the stimulation of activity by rats in the FST and the open field test.