FACTORS REGULATING DRUG CUE SENSITIVITY - THE EFFECT OF FRUSTRATIVE NONREWARD IN FENTANYL-SALINE DISCRIMINATION

Abstract

Rats were trained to discriminate 0.04 mg/kg of fentanyl from saline in a 2-lever food-reinforced procedure. The effects were studied of a manipulation of reinforcement (i.e., frustrative non-reward; FNR) on several characteristics of fentanyl-saline discrimination and codetermined response bias; symmetrical FNR in both types of sessions had no effect. Asymmetrical FNR in saline sessions steepened the slope of the generalization of fentanyl, but also of morphine and sufentanil; asymmetrical FNR in drug sessions flattened the gradient''s slope. Symmetrical FNR had effects on slope which were similar to those of asymmetrical FNR in saline sessions. Both symmetrical and asymmetrical FNR also appeared to affect the ED50 value of different agonists, and the ED50 value of naloxone in antagonizing 0.04 mg/kg of fentanyl. Apparently, reinforcement plays a major role in the acquisition of fentanyl-saline discrimination and in the quantitative characteristics of the stimulus generalization gradient of fentanyl and other agonists. The training drug itself may interact with the effects of FNR on its own gradient.