Vasopressin has general rate-decreasing effects on schedules maintaining either high or low response rates

Male and female Wistar rats were treated with different doses of vasopressin (0.05, 0.25, 1.25, 3.75 and 6.25 micrograms/kg) after responding had stabilized on either a differential reinforcement of low rate 15 s (DRL 15 s) or a differential reinforcement of high rate 0.75 s (DRH 0.75 s) schedule of reinforcement. Low to moderate doses of vasopressin did not affect response rates, response efficiency or the number of reinforcers obtained during vasopressin sessions on both the DRL and DRH schedules. Administration of 6.25 micrograms/kg vasopressin reduced low response rates and the number of reinforcers obtained during vasopressin sessions, but increased response efficiency. High response rates and response efficiency were reduced after administration of 3.75 and 6.25 micrograms/kg vasopressin, while the number of reinforcers obtained during vasopressin sessions was reduced at 6.25 micrograms/kg. Sex differences in the effects of vasopressin were not observed on either schedule.