ACUTE IMMOBILIZATION STRESS REDUCES (+ -)DOI-INDUCED 5-HT2A RECEPTOR-MEDIATED HEAD SHAKES IN RATS/

Acute immobilization stress induced by taping four limbs, applying tai l pinch stress and electric foot shock stress immediately reduced the frequency of head shakes induced by 1-(2,5-dimethoxy-4-iodophenyl)-2-a minopropane ((+/-)DOI), a 5-HT2A/C agonist in rats. Immobilization str ess due to the use of cylinder restraint and forced swimming did not a ffect 5-HT2A-mediated behavior, Acute immobilization stress did not af fect [H-3]ketanserin binding to the 5HT(2A) receptor in the prefrontal cortex and hippocampus. Presynaptic serotonergic lesions with 5,7-dih ydroxytryptamine (5,7-DHT) did not affect the reduction in 5-HT2A-medi ated behavior after acute immobilization stress. The decreases in head shake frequency after acute immobilization stress by taping were atte nuated by pretreatment with diazepam (2.5 mg/kg IP): This attenuation was reversed by pretreatment with flumazenil (10 mg/kg IP). The reduct ion 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.