DISCRIMINATIVE STIMULUS PROPERTIES OF NARCOTIC ANALGESIC DRUGS

This paper presents a comprehensive review on the experimental data relevant to the discriminative stimulus properties of narcotic analgesic drugs. The narcotic cue is defined as the discriminative stimulus complex which is exclusively associated with the specific central action(s) of narcotic analgesic drugs. The first part of this review discusses evidence that narcotics can act as a discriminative stimulus, and that this cue is an exclusive, complexly composed, and centrally originating property of narcotics. The pharmacological and biochemical specificity of the narcotic cue is supported by findings indicating (1) that chemically heterogenous narcotics generalize with narcotic agonist training drugs, (2) a close correlation between narcotic cuing and analgesic potency of narcotics, (3) that the requirement of steric specificity applies, and (4) the naloxone-reversibility of this cue. The comparative data so far available are thus consistent with the assumption that the narcotic cue in laboratory animals relates intimately to, and can serve as a preclinical model for opiate-like subjective effects in man. Further discussion is concerned with the involvement of various neurotransmitter substances in the narcotic cue; much as it appears likely that multiple and diffusely organized brain sites rather than discrete brain areas are involved, there is no evidence at this stage that any single transmitter would play a unique role in this cue. The other issues being discussed here are (1) the role of training drug dose, (2) the tolerance problem, (3) the relation between the narcotic cuing and the analgesic activity of narcotics, (4) the involvement of neuropeptides, (5) drug cue conditioning to environmental stimuli; (6) drug cues and drug states, and (7) the internal discriminative stimulus control of behavior by endogenous opioid substances. © 1978.