Dose-dependent antinociceptive action of neurotensin microinjected into the rostroventromedial medulla of the rat

Microinjection of neurotensin into the rat rostroventromedial medulla produces dose-dependent inhibition of the tailflick reflex (ED₅₀ of 2.06 nmol/animal (1.33–3.19)). The peak effect occurs 15–20 min following injection and, at the highest dose used, lasts up to 70 min.