Robert H. Bennett

Human aggressive responding during acute tobacco abstinence: effects of nicotine and placebo gum

Aggressive and point maintained operant responding of heavy nicotine dependent male tobacco smokers were measured during five 25-min sessions conducted over an 8-h period. Responding under three tobacco abstinence conditions was compared to responding during a baseline condition of ad libitum smoking of the subjects preferred brand of cigarettes. The three tobacco abstinence conditions were: (1) placebo gum, (2) nicotine gum or (3) no gum. Under placebo and nicotine gum conditions, subjects were given two pieces of placebo or 2 mg nicotine gum to chew for 30 min prior to each session. Expired air carbon monoxide (CO) levels were measured at the end of each session to monitor smoking under baseline conditions and compliance with non-smoking requirements under abstinence conditions. Aggressive responding was increased in no gum and placebo gum conditions, with the highest frequency of aggressive responding occurring under no-gum conditions. Aggressive responding during nicotine gum conditions did not differ from baseline ad libitum tobacco smoking. Point maintained responding was either not affected or decreased under placebo and no-gum conditions. These results provided objective data consistent with clinical reports of increased irritability among dependent tobacco smokers during acute tobacco abstinence.

EFFECTS OF ALCOHOL ON ROTARY PURSUIT PERFORMANCE : A GENDER COMPARISON

For 6 days, 10 male and 10 female social drinkers performed a rotary pursuit task six times across each day under both placebo and alcohol-intoxicated conditions. Following a training period, 0.35g/kg of alcohol or placebo beverages were administered 45 min before the second, third, and fourth sessions each day. In general, alcohol impaired the rotary pursuit performance of women more than that of men despite similar peak BAC levels. Results suggest no evidence of acute tolerance, evidenced by similar performance on the ascending and descending limbs of the BAC curve. However, results suggest that across the two alcohol administration days, men tended to develop some tolerance to the deleterious effect of alcohol on performance, whereas women became more sensitive to the effect of alcohol on performance. These results indicate that there may be gender differences in the effects of repeated alcohol administration on motor performance.

Effects of nicotine on cooperative responding among abstinent male smokers.

The effects of nicotine on human cooperative responding in abstinent male smokers were examined. During episodes occurring at random times through a session, concurrently available cooperative and independent responses were maintained by points exchangeable for money. Cooperative responses simultaneously added points to counters marked “Your Earnings” and “Others Earnings” only if the subjects and another persons responses ostensibly coincided. Independent responses added points only to the counter marked “Your Earnings”. After the first daily session abstinent subjects smoked ad libitum, received either 0, 2 or 4 mg nicotine gum or abstained from smoking. Increases from this first session in time allocated to the cooperative response option, proportion of cooperative responses and cooperative response rate were significantly greater following ad libitum smoking or acute administration of 4 mg nicotine. No effects of nicotine abstinence were observed on independent response rate. These results suggest effects on sociability may maintain nicotine use and increase relapse risk in abstinent smokers.

Benzodiazepine-induced impairment of matching-to-sample performance in humans

The effects of benzodiazepines on a visual pattern matching-to-sample (MTS) task were examined in nine healthy male volunteers. The MTS task employed randomly generated checkerboard-like stimuli presented on a video display. The sample and two comparison stimuli were simultaneously presented. Nonmatching comparison stimuli were randomly generated to be 3.125, 6.25, 12.5, 25.0, 37.5, or 50.0 percent different from the sample. Subjects responded on left or right button manipulanda to identify the matching comparison stimulus. The nonmatching stimulus condition was maintained constant for a 60-sec component and the percentage difference of the nonmatching stimuli was systematically varied across multiple components. The effects of triazolam (2.25-9.0 micrograms/kg) and lorazepam (7.5-45 micrograms/kg) were examined in a within-subjects, double-blind, placebo-controlled study. Under placebo conditions, response rates and accuracy were a positive function of the nonmatching stimulus discriminability. Triazolam produced dose-related decreases in response rate at nonmatching stimulus conditions greater than or equal to 25%. Only the 9.0 micrograms/kg dose of triazolam decreased accuracy and this occurred across all nonmatching stimulus conditions. Lorazepam effects were qualitatively similar but less robust than those of triazolam.

Punished and Nonpunished Responding in A Multiple Schedule in Humans: A Brief Report

Four male subjects responded on a multiple schedule in which responding was maintained by a random interval 20-sec (RI20) schedule of point presentation. Responding was suppressed in alternating components by an added variable ratio 30 (VR30) schedule of point subtractions. Each component was accompanied by distinctive stimulus lights. Subjects were exposed to the multiple schedule from the initial session. Two subjects experienced four 50-min sessions daily (Experiment 1) and the other two subjects participated in one 50-min session daily (Experiment 2). Once responding in the punished components had stabilized, responding in the nonpunished components continued to increase across sessions. Nonpunished responding did not stabilize even after as many as 36 sessions. These results are discussed in the context of previous studies using animals which employed multiple schedules with punished and nonpunished response contingencies.

Effects of spirometric administration of tobacco smoke containing varying amounts of nicotine on physiological measures and subject ratings.

A previously developed spirometric methodology of tobacco smoke administration was evaluated by determining the effects of varying nicotine delivery on various physiological and subjective measures. Eight male tobacco smoking subjects were administered 60 cc volumes of tobacco smoke drawn from University of Kentucky research cigarettes, or air. Subjects were exposed to four bouts of smoke administration conducted over an 8 h day. Each smoking bout was separated by 2 h and involved 20 smoke administrations at the rate of one every 30 sec. Each smoke administration consisted of 60 cc of air or 60 cc drawn from 0.3, 1.2 or 2.7 mg nicotine yield cigarettes, followed by 1 liter of air which forced the smoke or air deep into the lungs. Carbon monoxide (CO), blood pressure, and heart rate were measured before and after each smoking bout, and subject ratings of smoke effects were completed after each smoking bout. In a separate study, blood samples were collected on two occasions before and after administration of the two highest nicotine yield cigarettes to determine changes in nicotine plasma levels. Data indicated that the spirometric method produced: (1) similar CO boosts across nicotine yields, and (2) changes in heart rate, blood pressure, subject ratings and plasma nicotine levels which were directly related to the nicotine yield of cigarettes.

Ethanol-related cues and behavioral tolerance to ethanol in humans

The present study examined the effect of ethanol-related cues in the natural environment of the social drinker (e.g., a bar setting) upon performance on a behavioral task. Fourteen male social drinkers participated in the study. Half were designated low drinkers (3 or fewer drinks per week and little or no experience in bars) and half of the subjects comprised a moderate drinking group (8 to 15 drinks per week and drinking in bars at least 4 times per month). Subjects played a computer-controlled video game prior to and following consumption of a drink containing ethanol and orange juice. Each subject participated for one session in two different environmental settings, a standard experimental room and a room decorated to resemble a bar situation. The results showed significantly more detrimental effect of the ethanol upon performance in the standard experimental room than in the bar setting, that is, more tolerance was exhibited in the bar setting. However, no difference was observed between groups, that is, no effect of drinking experience and bar experience upon the relative amount of tolerance exhibited.