BEHAVIOR MAINTAINED UNDER A 2ND ORDER SCHEDULE BY INTRAMUSCULAR INJECTION OF MORPHINE OR COCAINE IN RHESUS-MONKEYS

  • 1 January 1976
    • journal article
    • research article
    • Vol. 199  (1) , 278-286
Abstract
Rhesus monkeys (3) lived in primate cages provided with response keys and enclosed in isolation chambers. During experimental sessions on Monday, Wednesday and Friday, the chamber door was closed and every 10th key-pressing response during a 60 min interval produced a 2 s red light, but had no other programmed consequences (the 10-response fixed-ratio component of the 2nd-order schedule; FR 10). The 1st FR 10 component completed after the 60 min interval had elapsed produced a red light which remained on for 2 min while the chamber door was opened; the monkey then extended his arm and was given an i.m. injection of drug (the 60 s fixed-interval component of the 2nd-order schedule; FI 60 min). Under this 2nd-order schedule of i.m. drug injection, repeated sequences of rapid responding were maintained during each session by 0.75 to 3.0 mg/kg injections of either morphine or cocaine. Patterns of responding characteristic of FR schedules were controlled by the 2 s red lights; a pause in responding after each 2 s red light was followed by a sustained high rate of responding until the light was produced again. Pauses in responding became progressively shorter as time elapsed in the 60 min interval. When saline injections were substituted for drug injections, responding markedly decreased. When responding was maintained by 3.0 mg/kg morphine injections, pretreatment with 0.03 mg/kg of nalorphine increased responding, while pretreatment with 0.1 or 0.3 mg/kg of nalorphine decreased responding.