Response of the rat tail artery to prolonged exposure to noradrenaline

1. The contractions of the rat tail artery in response to noradrenaline applied for 30 min periods were recorded under conditions that potentiate the vascular escape phenomenon (spontaneous partial relaxation in the continued presence of a vasoconstrictor) in smaller arteries. 2. The conditions were elevated temperature (from 32-37 degrees C), 500 nM forskolin and 10 microM 3-isobutyl-1-methyl xanthine. 3. None of these conditions caused any change in the time-course of constriction in response to noradrenaline, or produced any evidence of vascular escape in this large artery.