EFFECTS OF DOSE AND INTERDOSE INTERVAL ON LOCOMOTOR SENSITIZATION TO THE DOPAMINE AGONIST QUINPIROLE

To assess whether the interval between injections affects the course o f locomotor sensitization to quinpirole, groups of rats were injected every 2, 4, or 8 days with quinpirole (0, 0.025, 0.25, 0.5, and 2.5 mg /kg; n = 222) and their locomotor activity monitored after each inject ion for a total of 10 tests. Results indicate that the number of drug injections, rather than the interval between them, predominantly contr ols the development of locomotor sensitization to quinpirole. It is su ggested that this may reflect a rapid induction but slow decay time fo r a response-enhancing factor stimulated by each injection of quinpiro le, and that the effects of this putative factor are cumulative but sa turable.