ASSESSMENT OF 8-OH-DPAT INDUCED SPONTANEOUS TAILFLICKS AS AN IN-VIVO MODEL OF 5-HT(1A) FUNCTION IN YOUNG-RATS

Spontaneous tailflicks, measured as elevation of the tail above the body axis in restrained animals, have been studied in both adult and young rats. The selective 5-HT1A agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT), induced dose-related increases in spontaneous tailflicks in adult (> 60 days) male rats. These responses were antagonised by the 5-HT1A antagonists (-)-propranolol and (-)-pindolol. 8-OH-DPAT (1 mg/kg) induced tailflicks could be observed in 30, 25 and 20 day old male rats and were also antagonised by (-)-propranolol and (-)-pindolol although drug-induced rotation of the 20 and 25 day old animals hindered assessment. At 14 and 10 days, 8-OH-DPAT (1 mg/kg) produced Straub tail responses which precluded the observation of tailflicks. Lower doses of 8-OH-DPAT, which did not elicit Straub tail in these younger animals also failed to produce tailflicks. Thus 8-OH-DPAT induced spontaneous tailflicks reflect in vivo activation of 5-HT1A receptors in adult and 30 day old male rats but are inappropriate for the study of 5-HT1A mediated behaviour in younger animals.