Changes in brain serotonin turnover, body and head shakes in kainic acid-treated rats

Kainic acid induces seizures and neurotoxicity in rats, produces changes in brain serotonin (5-HT), dopamine and noradrenaline metabolites among other changes in neurotransmitters. In this work, we investigated the changes in 5-HT turnover in brain regions from 84 rats intraperitoneally injected with kainic acid and a specific behavioural change, the body and head shakes, exerted by this neurotoxin in the presence of 5-HT receptor antagonists. Kainic acid produced an increase in 5-hydroxyindoleacetic acid levels in frontal cortex (212%; 180%), striatum (177%; 116%), amygdala (202%; 337%) and hippocampus (43%; 70 %) at 2 and 24 hr as compared with controls, respectively. Serotonin turnover was increased in amygdala (157%) and frontal cortex (169%) at 2 hr; whereas 24 hr after kainic acid administration, increases were observed in amygdala (207%), and frontal cortex (178%). Kainic acid also produced an increase in the frequency of head and body shakes when administered alone or together with pargyline, a monoamine oxidase inhibitor; whereas the administration of 5-HT receptor antagonists such as ketanserin and methiothepin, decreased this behaviour 54% and 50% as compared with kainic acid alone, respectively. These results suggest an active participation of 5-HT neurotransmission on the excitotoxic action of kainic acid in the brain.