The effects of extrinsic context on nicotine discrimination

Configurations of the interoceptive discriminative stimulus effects of ethanol and nicotine with two different exteroceptive contexts in rats: Extinction & recovery

Interoceptive states interact with exteroceptive contexts in modulating operant behavior, which is maintained by its consequences. Evaluating discriminative stimulus control by overlapping interoceptive and exteroceptive configurations (gestalts) and the contribution of each modality may be clinically important for understanding aspects of relapsing behavior (e.g., drug abuse). With rats, the current investigation used a completely counterbalanced one-manipulandum operant drug discrimination procedure that established discriminative stimulus control between nicotine (0.3mg/kg) in one exteroceptive context and EtOH (1.0g/kg) in a differing exteroceptive context. One combined interoceptive-exteroceptive condition occasioned sessions of food reinforcement (S(D)) and the other counterbalanced condition occasioned sessions of non-reinforcement (S(Δ)). Each stimulus modality contributed to discriminative control, but to lesser extents than the combined intero-exteroceptive compound configurations (Experiments 1 & 2). In Experiment 1, responding was extinguished in the interoceptive stimulus conditions alone in a neutral exteroceptive context, but then renewed by reconfiguring the drugs with the exteroceptive contexts, and reversed in the opposing exteroceptive contexts. In Experiment 2, responding was extinguished in the interoceptive and exteroceptive contexts separately. Reconfiguration of the full intero-exteroceptive compound configurations did not promote recovery. These results suggest that interoceptive and exteroceptive discriminative control can be methodologically configured in modulating operant behavior during acquisition, extinction, and recovery of behavior; however, configuring interoceptive and exteroceptive discriminative stimuli do not appear to function as unique cues that differ from each stimulus modality alone. Clinical implications are discussed.

Discriminative stimulus effects of nicotine in humans

Behavioral discrimination procedures clearly demonstrate that nicotine elicits interoceptive stimulus effects in humans that are malleable by various pharmacological manipulations as well as by some behavioral manipulations. The parameters of nicotine discrimination and both chronic and acute factors that may alter discrimination behavior are addressed in this chapter, which emphasizes research by the author involving nicotine delivered by nasal spray. Human discrimination of nicotine is centrally mediated, as the central and peripheral nicotine antagonist mecamylamine blocks discrimination but the peripheral antagonist trimethaphan does not. The threshold dose for discrimination of nicotine via spray appears to be very low in smokers as well as nonsmokers. Because smoked tobacco delivers nicotine more rapidly than spray, the threshold dose of nicotine via smoking is probably even lower. In terms of individual differences, smokers may become tolerant to the discriminative stimulus effects of higher nicotine doses but not of low doses. Men may be more sensitive than women to nicotine's discriminative stimulus effects, consistent with other research suggesting that nicotine is more reinforcing in men than in women. Other potential individual differences in nicotine discrimination have not been clearly tested, but may include genetics, obesity, and dependence on other drugs. Acute environmental factors that alter nicotine discrimination include the specific training and testing conditions, pointing to the need for careful control over such conditions during research. Other factors, such as concurrent acute use of alcohol or caffeine, do not appear to alter nicotine discrimination, suggesting that changes in nicotine discrimination are not likely explanations for the association of smoking behavior with use of those drugs. Concurrent physical activity also does not appear to alter nicotine discrimination, indicating that results from studies of discrimination in subjects at quiet rest, the standard approach in this research, generalize well to discrimination in subjects engaged in various activities, as often occurs in the natural environment. Future research should more clearly examine the potential role of nicotine's discriminative stimulus effects in nicotine reinforcement and determine the generalizability of these findings to nicotine delivered by other means, particularly tobacco smoking.

Impairment in Cognitive Functions After Multiple Detoxifications in Alcoholic Inpatients

BACKGROUND

Repeated experience of withdrawal from alcohol results in a kindling-like process leading to increased likelihood and severity of convulsions during detoxification. The aim of this study was to determine whether repeated withdrawals affect cognitive function.

METHODS

We investigated alcoholic patients undergoing detoxification in an inpatient setting, using tasks sensitive to dysfunction of prefrontal areas. The tasks applied were two maze tasks from the Wechsler Intelligence Scale for Children, the color Stroop task, and the vigilance task for adults and the delay task from the Gordon Diagnostic System. Forty-two abstinent alcoholic patients who were no longer receiving pharmacotherapy for detoxification participated.

RESULTS

Compared to a group of forty-three social drinkers matched for age, sex, and verbal IQ, the alcoholic patients took more time to complete maze 1 and made more errors in both mazes. Alcoholics made more commission errors and gave fewer correct answers in the vigilance task. No differences were found in the color Stroop task between alcoholic patients and social drinkers. Patients with 2 or more detoxifications were more impaired in the maze 1, in the vigilance task and in the delay task than patients with a single, or no previous detoxification. When patients were reclassified on the basis of the total number of attempts at withdrawing from alcohol (including the medically supervised) only the deficit in the vigilance task was associated with the number of withdrawal attempts. The effects of medically supervised detoxifications on maze 1 and vigilance task were confounded with other factors related to the history of alcoholism, alcohol use, age of starting heavy drinking and years of problem drinking.

CONCLUSIONS

Repeated experience of withdrawal from alcohol is thus associated with impaired cognitive function although it appears that for some of these effects, other factors associated with the history of alcoholism might also be involved.