Acute immobilization stress reduces (+/-)DOI-induced 5-HT2A receptor-mediated head shakes in rats.

Acute immobilization stress induced by taping four limbs, applying tail pinch stress and electric foot shock stress immediately reduced the frequency of head shakes induced by 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane ((+/-)DOI), a 5-HT2A/C agonist in rats. Immobilization stress due to the use of cylinder restraint and forced swimming did not affect 5-HT2A-mediated behavior. Acute immobilization stress did not affect [3H]ketanserin binding to the 5HT2A receptor in the prefrontal cortex and hippocampus. Presynaptic serotonergic lesions with 5,7-dihydroxytryptamine(5,7-DHT) did not affect the reduction in 5-HT2A-mediated behavior after acute immobilization stress. The decreases in head shake frequency after acute immobilization stress by taping were attenuated by pretreatment with diazepam (2.5 mg/kg IP): This attenuation was reversed by pretreatment with flumazenil (10 mg/kg IP). The reduction in (+/-)DOI-induced 5-HT2A-mediated behavior caused by stress may be related to a change in agonist affinity to the receptor or changes in other neurotransmitter systems or the effect of PI turnover.