Assessment of 8-OH-DPAT induced spontaneous tailflicks as an in vivo model of 5-HT1A 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.