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Biomedical subjects

S T Higgins

Publications and source records attributed to S T Higgins.

At least 91 records · Page 5Linked to original sources
PubMed1992

Caffeine drug discrimination in humans: acquisition, specificity and correlation with self-reports.

This study evaluated the discriminative stimulus effects of caffeine in humans. Nine normal male and female volunteers (ages 18-28) were trained to discriminate between the methylxanthine central nervous system stimulant caffeine (320 mg/70 kg, p.o.) and placebo. Monetary reinforcers were earned for identifying correctly the letter code associated with each substance. After four training sessions, the ability to discriminate between the two training conditions was tested for 20 sessions (test-of-acquisition). In subjects who met the criterion for discrimination (i.e., greater than or equal to 85% correct responding on greater than or equal to 4 consecutive sessions during the last 10 test-of-acquisition sessions) dose-effect curves for caffeine (0, 56, 100, 180, 240 and 320 mg/70 kg) and for the benzodiazepine triazolam (0, 0.10, 0.32 and 0.56 mg/70 kg) were determined. Seven of the nine subjects learned the caffeine-placebo discrimination and their performance improved across the 20 test-of-acquisition sessions. The training dose of caffeine (320 mg/70 kg) produced stimulant-like self-reports that differed from placebo when the letter codes were identified correctly, but not when the letter codes were identified incorrectly. Novel caffeine doses produced dose-related increases in caffeine-appropriate responding (N = 4), whereas triazolam produced predominantly placebo-appropriate responding (N = 3) and self-reports that differed from both caffeine and placebo. Throughout dose-effect curve determinations, the training dose of caffeine and placebo continued to be identified correctly (range: 84-100% correct responding). These results suggest that a caffeine (320 mg/70 kg)-placebo discrimination 1) can be acquired and maintained, 2) is related to self-reported drug effects if the training conditions are correctly identified and 3) has some pharmacological specificity.

Adult↗
PubMed1991

Caffeine self-administration, withdrawal, and adverse effects among coffee drinkers.

Twenty-two coffee drinkers (three to seven cups per day) underwent repeated double-blind trials to test for caffeine self-administration, withdrawal, and adverse effects. Each trial consisted first of a randomized crossover period of 1 day of decaffeinated coffee and 1 day of caffeinated coffee (100 mg) to assess withdrawal and adverse effects of caffeine. Next, subjects were given 2 days of concurrent access to the two coffees. The relative use of the two coffees was used to assess caffeine self-administration. Reliable caffeine self-administration occurred in three of 10 subjects in study 1 and seven of 12 subjects in study 2. Withdrawal symptoms were headaches, drowsiness, and fatigue. The major adverse effect from self-administration was tremulousness. The occurrence of headaches on substitution of decaffeinated coffee prospectively predicted subsequent self-administration of caffeine. These results indicate that some coffee drinkers exhibit signs of a caffeine dependence, ie, they self-administer coffee for the effects of caffeine, have withdrawal symptoms on cessation, and experience adverse effects.

Adult↗
PubMed1991

Effects of caffeine on tobacco withdrawal.

Smoking cessation increases caffeine blood levels, and this has been hypothesized to cause some of the symptoms of tobacco withdrawal (e.g., anxiety and insomnia). To test this hypothesis, 10 coffee drinkers who smoked cigarettes were entered into a completely within-subjects experimental design in which the effects of caffeine dose (0, 50, and 100 mg/coffee serving) and smoking status (smoking versus abstinence) were examined over a 4-day period. Self-reported and observed measures of tobacco withdrawal, caffeine withdrawal, and intoxication, as well as psychomotor tasks and vital signs, were completed daily; blood was drawn at the end of each period. Temporary abstinence produced typical withdrawal symptoms but did not significantly increase caffeine blood levels. Caffeine did not increase the severity of symptoms but did decrease the severity of withdrawal-induced hunger. These findings suggest that, in the absence of increased blood levels, caffeine does not increase the severity of tobacco withdrawal.

Adult↗
PubMed1991

A behavioral approach to achieving initial cocaine abstinence.

OBJECTIVE: The aim of this study was to assess the efficacy of a behavioral treatment program for achieving initial cocaine abstinence in individuals enrolled in outpatient treatment for cocaine dependence. METHOD: Thirteen consecutively admitted outpatients were offered behavioral treatment consisting of contingency management procedures and the community reinforcement approach. Fifteen consecutively admitted outpatients were offered treatment with 12-step counseling. All 13 of the patients who were offered the behavioral treatment accepted it; 12 of the patients offered 12-step counseling accepted it. RESULTS: Eleven of the 13 patients in the behavioral treatment were retained for 12 weeks of treatment, compared with five of the 12 patients given 12-step counseling. Ten of the patients given behavioral therapy achieved 4 weeks of continuous cocaine abstinence, compared with only three of those given 12-step counseling. Six of the patients in the behavioral treatment group achieved 8 weeks, and three achieved 12 weeks; none of the patients in the 12-step counseling program achieved 8 weeks. CONCLUSIONS: The behavioral treatment described in this paper offers promise as an effective intervention for achieving initial cocaine abstinence. A randomized trial is underway to assess the generality of these findings.

Adult↗
PubMed1991

Contingent reinforcement of abstinence with individuals abusing cocaine and marijuana.

Two males diagnosed with cocaine dependence received a behavioral intervention comprised of contingency management and the community reinforcement approach. During the initial phase of treatment, reinforcement was delivered contingent on submitting cocaine-free urine specimens. The community reinforcement approach involved two behavior therapy sessions each week. Almost complete cocaine abstinence was achieved, but regular marijuana use continued. During a second phase, reinforcement magnitude was reduced, but remained contingent on submitting cocaine-free specimens. Behavior therapy was reduced to once per week. Cocaine abstinence and regular marijuana use continued. Next, reinforcement was delivered contingent on submitting cocaine- and marijuana-free specimens. This modified contingency resulted in an abrupt increase in marijuana abstinence and maintenance of cocaine abstinence. One- and 5-month follow-ups indicated that cocaine abstinence continued, but marijuana smoking resumed. These results indicate that the behavioral intervention was efficacious in achieving abstinence from cocaine and marijuana; maintenance, however, was achieved for cocaine only.

Adult↗
PubMed1991

Behavioral economics of drug self-administration. II. A unit-price analysis of cigarette smoking.

In behavioral economics, the ratio of response requirement to reinforcer magnitude is referred to as unit price. Previous research with nonhuman subjects has demonstrated that (a) comparable amounts of food are consumed at the same unit price even though different response requirements and reinforcer magnitudes comprise that unit price and (b) increases in unit price decrease food consumption in a positively decelerating fashion. The present study assessed the generality of these findings to the cigarette smoking of 5 human volunteers. During approximately 18 3-hr sessions, various combinations of response requirement (fixed-ratio 200, 400, and 1,600) and reinforcer magnitude (1, 2, and 4 puffs per bout) were arranged. Consumption (i.e., the number of puffs) generally was comparable at the same unit price independent of the response requirement and reinforcer magnitude comprising that unit price. In addition, increasing unit price generally decreased consumption in a positively decelerating fashion. These results extend the generality of the unit-price analysis to human cigarette smoking. Moreover, these results further support the position that reinforcer magnitude and response requirement are functionally equivalent and interact to determine consumption. The concept of unit price, by integrating and summarizing the effects of those two operations, provides a more parsimonious explanation of the results than do separate evaluations of the effects of response requirement and reinforcer magnitude.

Adolescent↗
PubMed1991

The effects of schedule history and the opportunity for adjunctive responding on behavior during a fixed-interval schedule of reinforcement.

The effects of schedule history and the availability of an adjunctive response (polydipsia) on fixed-interval schedule performance were investigated. Two rats first pressed levers under a schedule of food reinforcement with an interresponse time greater than 11 s, and 2 others responded under a fixed-ratio 40 schedule. All 4 were then exposed to a fixed-interval 15-s schedule. Water was continuously available under these conditions, but after responding became stable on the fixed-interval schedule, access was experimentally manipulated. With water freely available, subjects did not display characteristic fixed-interval response rates and patterns (i.e., scalloping or break-and-run). Instead, they exhibited predictable, stable patterns of behavior as a function of their schedule histories: Subjects with the interresponse-time history exhibited low response rates, and those with the fixed-ratio history exhibited high rates. Manipulating the amount of water available resulted in marked changes in response rates for rats with the interresponse-time history but not for those with the fixed-ratio history. The results illustrate the multiple causation of behavior by its previous and current schedules of reinforcement and other concurrent factors.

Animals↗
PubMed1991

The effects of diazepam and triazolam on repeated acquisition and performance of response sequences with an observing response.

Drugs often disrupt the acquisition of new response sequences at doses that fail to disrupt the performance of a previously acquired response sequence. This selective drug effect may result from differences in the control exerted by the stimuli presented after each response in the acquisition and performance sequences. To examine the function of these stimuli, an observing procedure was incorporated into a multiple schedule of repeated acquisition and performance of response sequences, in which stimulus presentations were contingent upon an observing response. Three experiments were conducted with humans. Experiment 1 compared responding with and without the observing contingency. No difference was found in the overall percentage of errors across the two conditions. Within the observing condition, observing behaviour was maintained in the acquisition component as long as errors occurred, but was not maintained in the performance component. Experiment 2 examined whether a contingency that increased errors also would increase observing in both the acquisition and performance components. Specifically, reinforcer delivery in each component was contingent upon emitting 10 correct responses and one, two, or four errors. Observing responses increased in the acquisition component as the error requirement increased, whereas observing responses in the performance component increased only when the error requirement was four. Experiment 3 assessed the effects of diazepam (0, 7.5, 15, and 30 mg/70 kg, p.o.) and triazolam (0, 0.375, and 0.75 mg/70 kg, p.o.) on repeated acquisition and performance baselines with the observing contingency. Selective drug effects were obtained in this modified procedure; that is, the percentage of errors in the acquisition component increased at doses that failed to affect the percentage of errors in the performance components. Importantly, drug effects were selective, even though observing responses were not emitted in the performance component and, hence, the stimulus presentations did not occur in that component. These findings suggest that alternative explanations for these differential effects are needed; in that regard, a response-unit account of the selective drug effects is discussed.

Adult↗
PubMed1991

Buprenorphine for pain relief in a patient with drug abuse.

Buprenorphine is a mixed opioid agonist/antagonist which appears to produce less physical dependence and respiratory depression than typical mu-agonist opioids. These effects suggest its use for analgesia for drug abusers. However, buprenorphine may precipitate withdrawal from other opioids. The present case illustrates the utility of buprenorphine and describes a method to transfer a patient from a mu-agonist to buprenorphine without precipitating withdrawal or interrupting analgesia.

Adult↗
PubMed1991

Long-term use of nicotine vs placebo gum.

Medical patients (n = 315) who wished to quit smoking were randomly assigned in a double-blind manner to receive either nicotine or placebo gum. Subjects were advised to stop gum use by 4 months. Among abstinent smokers, 46% of those receiving nicotine gum and 17% of those receiving placebo gum used the gum beyond the recommended 4-month period. By 10 months after cessation 17% of quitters receiving nicotine gum and 6% receiving placebo gum were still using gum. Gradual reduction of nicotine gum did not result in withdrawal and cessation of nicotine gum did not increase the probability of relapse to smoking or weight gain. We conclude that use of nicotine gum is due, in part, to the effects of nicotine; however, long-term use is uncommon.

Adult↗
PubMed1990

Effects of intranasal cocaine on human learning, performance and physiology.

The behavioral and physiological effects of intranasally administered cocaine (placebo, 48, 96 mg/70 kg) were examined in eight recreational cocaine users under controlled laboratory conditions. The 48 and 96 mg doses of cocaine significantly improved subjects' performance on the Digit Symbol Substitution Test above levels observed either prior to drug administration or when placebo was administered. These effects were discernible for up to 120 min after cocaine administration. Cocaine had no statistically significant effects on learning and performance of ten-response sequences. The 48 and 96 mg doses increased heart rate and blood pressure for up to 180 min, and increased subject ratings of drug effects and decreased skin temperature for 60-90 min after drug administration. Cocaine produced no significant effects on the electrocardiogram. To our knowledge, this is the first experimental demonstration that acutely administered cocaine can improve behavioral performance in rested subjects. In addition, the duration of cardiac effects in this study was longer than previously reported with intranasal cocaine, perhaps due to the concurrent behavioral testing.

Administration, Intranasal↗
PubMed1990

Behavioral economics of drug self-administration. I. Functional equivalence of response requirement and drug dose.

Response requirement and dose of drug per administration are two separate factors that have been demonstrated to control drug self-administration. Recent developments in behavioral economics have shown that these two factors are in fact functionally equivalent for nondrug reinforcers, as indicated by a unit-price analysis. In this review, the unit-price notion was tested for drugs as reinforcers via a re-analysis of ten drug self-administration studies. The results of the re-analysis indicated that response requirement and reinforcer magnitude, the constituents of unit price, have functionally equivalent effects on drug consumption and that a positively decelerating demand curve is produced as unit price increases. This suggests that the behavioral-economic notion of unit price is a more parsimonious explanation of the effects of response requirement and dose in drug self-administration studies, in that it integrates and describes what was previously considered to be two distinct operations.

Behavior↗