NITROUS-OXIDE - SENSORY, MOTOR, ASSOCIATIVE, AND BEHAVIORAL TOLERANCEEFFECTS IN CLASSICAL-CONDITIONING OF THE RABBIT NICTITATING-MEMBRANE RESPONSE

Experiment 1, of a series of six experiments with the rabbit nictitati ng membrane response (NMR) preparation, revealed that nitrous oxide (0 %, 33%, 67%) impaired acquisition of conditioned responses (CRs). Subs equent experiments indicated that nitrous oxide (N2O) had no reliable effects upon nonassociative processes experiment 2); impaired uncondit ioned response (UR) amplitude (Experiment 3); attenuated tone-conditio ned stimulus (CS) intensity (Experiment 4); decremented tone-induced r eflex modification of the unconditioned NMR (Experiment 5); and demons trated no reliable evidence of behavioral tolerance (Experiment 6). It was concluded that N2O's impairment of CR acquisition was attributabl e to its attenuation of the intensity of tone CSs and shock USs and/or UR amplitude. These findings are consistent with the behavioral laws of conditioning: the attenuation of the intensive sensory properties o f the CS and US and/or UR components of conditioning affect their abil ity to enter into the establishment of CS-CR connections and, therefor e, the development of associative learning.