A behavioral and pharmacological analysis of reinforcement withdrawal

Effects of chlordiazepoxide on pausing during rich-to-lean transitions

Extended pausing during discriminable transitions from rich-to-lean conditions can be viewed as escape (i.e., rich-to-lean transitions function aversively). Thus, an anxiolytic drug would be predicted to mitigate the aversiveness and decrease pausing. In the current experiment, pigeons' key pecking was maintained by a multiple fixed-ratio fixed-ratio schedule of rich (i.e., larger) or lean (i.e., smaller) reinforcers. Intermediate doses (3.0-10.0 mg/kg) of chlordiazepoxide differentially decreased median pauses during rich-to-lean transitions. Relatively small decreases in pauses occurred during lean-to-lean and rich-to-rich transitions. Effects of chlordiazepoxide on pausing occurred without appreciable effects on run rates. These findings suggest that signaled rich-to-lean transitions function aversively.

Effect of anxiolytics and antidepressants on extinction and negative contrast

Anxiolytics, particularly the benzodiazepines and barbiturates tend to retard, but not prevent, extinction, promote recovery from negative contrast, and elevate S- responding in discrimination training. Anxiolytics, administered during acquisition, tend to eliminate the partial reinforcement extinction effect, but this result is substantially influenced by parametric considerations. Behaviors that are energized in extinction may have a different pharmacological profile than behaviors that decline. Conclusions regarding the effects of antidepressants must be more tentative but, in general, acutely administered antidepressants are relatively ineffective in all of these paradigms. However, antidepressants may enhance the efficiency of responding on DRL schedules whereas anxiolytics tend to disrupt such behavior.

Flurazepam hydrochloride and its principal metabolites: behavioural studies in the monkey (Macaca mulatta)

Effects of flurazepam and its two principal metabolites, hydroxyethylflurazepam and desalkylflurazepam (0.5, 1.0, 3.0 and 10.0 mg/kg), were studied on a delayed differentiation task in the monkey. Flurazepam (10.0 mg/kg) and hydroxyethylflurazepam (3.0 and 10.0 mg/kg) decreased the number of correct responses and increased response latency; effects persisted to 4 h with the highest dose. Marked impairment of performance was observed with all doses of desalkylflurazepam and effects of 3.0 and 10.0 mg/kg persisted to 24 h. Evidence of a disinhibitory effect of desalkylflurazepam was demonstrated. The study would point to a consideration of both metabolites in the hypnotic effect and in the impairment of performance observed after acute ingestion of flurazepam in man.

The neurochemistry and pharmacology of extinction behavior

The role of various neurotransmitter systems in the brain in extinction behavior is examined. An attempt is made to suggest psychological mechanisms (such as attention, secondary reinforcement or internal inhibition) by which the neurotransmitter systems or drugs act to produce the observed alteration in extinction behavior. The putative neurotransmitters acetylcholine, noradrenaline, dopamine, serotonin, endorphins and the peptides are reviewed, as are pharmacological agents such as the benzodiazepines, the barbiturates, the psychodelics, the neuroleptics, the psychomotor stimulants and cannabinoids. Other treatments and factors are considered such as peripheral hormones and the adrenal-pituitary axis. It is suggested that the noradrenergic system may be involved in the expression of extinction behavior by a role in selective attention, the dopamine system via an involvement with secondary reinforcement, the cholinergic system by a mechanism of response inhibition and the barbiturates and benzodiazepines by a block of nonreward.

Scopolamine and acquisition of go-no go avoidance: a further analysis of the perseverative antimuscarinic deficit

Rats treated with scopolamine (0.5 mg/kg SC daily) during the acquisition of a discrimination task with symmetrical negative reinforcement (light-go, noise/light-no go) showed a learning impairment, with both active and passive avoidance deficits. In the initial stage of such training, however, fewer passive avoidance errors and more active avoidance errors were made by treated animals if active avoidance pretraining had occurred in the no-drug state. A similar experiment using the same stimulus arrangement with asymmetrical reinforcement (no punishment of intertrial, and no go signal, responses) showed a scopolamine effect consisting mainly of increased responding to extinction signals and during intertrial intervals, with little or no active avoidance deficit. Furthermore, interactions due to changes in treatment conditions in successive stages of training were minimized in the latter task, suggesting that the effects of the shift-no shift factor on distribution of errors in the early stages of active-passive avoidance learning were unlikely to have been due to a genuine drug dissociation. Overall, these results and others obtained previously in the same and related tasks tend to rule out some unidimensional explanations of antimuscarinic effects, e.g., response disinhibition (an exclusively motor deficit) or impairment of stimulus sensitivity (an exclusively sensory deficit). The data rather confirm the notion of a sensorimotor drug bias leading to a shift in response prepotencies depending jointly on stimuli, responses, and response consequences. Prior learning history and behavioural compensation for adverse treatment consequences at the reinforcement level may interact with the sensorimotor bias so as to produce "set perseveration" (perseveration of response tendencies).

Chlordiazepoxide-induced released responding in extinction and punishment-conflict procedures is not altered by neonatal forebrain norepinephrine depletion

The effects of chlordiazepoxide (CDZ) in extinction and punishment-conflict tasks were examined in rats after neonatal systemic administration of 6-hydroxydopamine (6-OHDA) to deplete forebrain norepinephrine (NE). At about 70 days of age the rats were water deprived and trained for three days to drink in a novel apparatus. On the fourth day (test day) drinking was either extinguished by elimination of water from the drinking tube or punished by lick-contingent shock. Just prior to this test session half of the vehicle and half of the 6-OHDA treated rats were given an injection of CDZ (8 mg/kg IP). Both the injection of CDZ and forebrain NE depletion prolonged responding during extinction and reduced the suppressant effects of punishment in male rats, and these effects were of similar magnitude. Furthermore, CDZ was as effective in neonatal 6-OHDA treated male rats as in vehicle treated rats indicating that decreased transmission is ascending NE fibers caused by CDZ is not solely responsible for its behavioral effects in extinction and conflict tasks. Rather, these effects may involve cooperative mediation by both noradrenergic and serotonergic forebrain terminals. Unexpectedly, CDZ's anti-extinction effect was absent in female rats and its anti-conflict effect observed only in NE depleted females.

Chlordiazepoxide and resistance to punishment

Rats were given intermittent electric foot-shock during food-rewarded alley training. In the test phase, food and shock were given on every trial. These animals persisted in running down the alley in the test phase compared to those without prior shock experience. The effects of chlordiazepoxide (CDP) on this learned resistance to punishment were examined using a long and short interval between trials. It was found that CDP abolished the effect at a long inter-trial interval, but left it unaltered if the interval was short. The results match those found previously with an analogous effect using non-reward. It is suggested that the effects of punishment and non-reward may be mediated by a common process, and that the benzodiazepines may act on this process.

Reward-induced stereotypy: modulation by the hippocampus

In animals with hippocampal damage, the signaled administration of reward is sufficient to induce the sort of behavioral sterotypy and locomotion that heretofore has been observed only after drug administration. Haloperidol returns these behaviors to normal. The interaction of the hippocampus with reward helps to explain many well-known characteristics of animals with lesions in the hippocampus and may have relevance for catecholamine-based clinical disorders.

Differential effects of methylphenidate on signalled and non-signalled reinforcement

Rats were trained to press a bar with water reinforcement under a variable interval 15-sec (VI 15), variable interval 15-sec signalled-reinforcement (VI SD), or a differential-reinforcement-of-low-rate 10-sec (DRL 10) schedule. Methylphenidate (MP) had little effect on response rates or reinforcements-earned in the VI 15 group. However, MP increased response rates in a dose-related manner in the VI SD and the DRL 10 groups. These findings and additional results reported in the literature suggest that signalled reinforcement does not necessarily antagonize the rate-increasing effects of the amphetamine-type drugs.

Effects of diazepam on extinction induced aggression in pigs

Pigs were trained to press a panel with their snout to get food in an operant conditioning chamber. Aggressive behaviour which developed between two pigs submitted together to extinction was used as a baseline to study the effects of 1-2 mg/kg diazepam. When access to the response panel and feeding area was permitted, diazepam enhanced resistance to extinction and did not modify aggression. When access to the response panel and feeding area was not permitted, diazepam increased the severity of aggression observed between the animals. In both instances, plasma corticosteroid levels were depressed in diazepam-treated pigs. These results suggest that benzodiazepines do not act on frustation or aggressiveness per se, but rather strengthen the prevailing behavioural attitudes in the animals' repertoire at the time of test.

The effects of scopolamine on extinction and spontaneous recovery

The effects of scopolamine hydrobromide on baseline extinction levels and spontaneous recovery were assessed. Rats were trained on one of four reinforcement schedules (CRF, FR 10, FR 20, FR 40) with either food or water reinforcement. Scopolamine increased response rates in extinction and spontaneous recovery following training on all four schedules when the reinforcer was water, but had no effect on responding previously maintained by food. The results are discussed in terms of the limitations of a general theory of a cholinergic system mediating all suppressed behavior and the effects of anticholinergic drugs on central thirst mechanisms and consummatory behavior.

Effect of chlordiazepoxide on the partial reinforcement extinction effect

Rats were trained to run in a straight alley under conditions of partial or continuous reinforcement. Extinction was slower after partial reinforcement. Chlordiazepoxide, administered during acquisition only, had no effect on acquisition but abolished the partial reinforcement extinction effect. The results support the hypothesis that chlordiazepoxide acts by attenuating the effects of averisive stimuli.

Effects of diazepam on behaviour suppressed by extinction in pigs

Diazepam injected to pigs previously trained to perform an operant response for food according to a continuous reinforcement schedule significantly increased resistance to extinction compared to control pigs. In pigs submitted to a time-out procedure diazepam increased the number of nonreinforced responses at the beginning of the acquisition but was unable to disinhibit suppressed behaviour in the later stages of acquisition when the extinguished behaviour was well acquired. The results are discussed with respect to antiaversive or disinhibitory effects of benzodiazepines and an alternative interpretation, the strengthening of the prevailing behavioural tendency in the animal's repertoire at the time of test, is put forward.

Effects of scopolamine, physostigmine and chlordiazepoxide on punished and extinguished water consumption in rats

It has been postulated that behavioral inhibition due to punishment or extinction may be mediated by brain acetylcholine, and drugs which have disinhibitory action are thought to interact with this system. This notion was tested by comparing the effects of scopolamine, physostigmine and chlordiazepoxide on punished and extinguished water consumption. Scopolamine hydrobromide (0.3, 0.5 mg/kg, i.p.), a centrally and peripherally acting antimuscarinic agent and physostigmine sulfate, (0.3 mg/kg, i.p.), a centrally and peripherally acting acetylcholinesterase inhibitor, lowered both non-punished and punishment suppressed water intake and lick rate, whereas their quaternary analogs which primarily act in the periphery, had no significant effect at comparable dose levels. Scopolamine and physostigmine suppressed punished water consumption at lower dose levels than nonpunished intake. In contrast, chlordiazepoxide (5.0, 10.0, 20.0 mg/kg, i.p.) enhanced punished as well as non-punished water intake. In a further experiment comparing punishment and extinction suppression, scopolamine and physostigmine did not affect punished or extinguished water intake; chlordiazepoxide (5.0, 10.0, 20.0 mg/kg) reliably increased punished, but not extinguished licking on the water nozzle. These results suggest (1) that scopolamine and chlordiazepoxide do not act via a common mechanism, and (2) that punishment and extinction suppression are not a pharmacological entity.

The effects of scopolamine on a two-cue discrimination

Rats were trained with a tone, light or a tone—light combination as the discriminative stimulus. These groups were tested after doses of scopolamine and it was found that groups trained with a single cue were more sensitive to the drug than double-cue groups, although their pre-drug responding was similar. A similar pattern was found among individuals in the double-cue groups in which there was a significant correlation between dependency on a single cue, as shown in transfer tests, and drug sensitivity. These results were interpreted in terms of scopolamine-induced changes in stimulus sensitivity produced by a modification of the neural mechanisms controlling attention.

Studies on the possible role of brain histamine in behaviour

1. The possible role of brain histamine in behavioural performance was studied in rats using thirst-induced water consumption, continuous (Sidman) avoidance, and reinforcement withdrawal test systems.2. Parenteral administration of a variety of antihistamines to rats decreased thirst-induced water consumption; this effect could be antagonized by administration of histamine directly into the brain by a ventricular cannula.3. When intraventricular doses of histamine were administered to rats at weekly intervals, an adaptation was seen in the effects of the amine on continuous avoidance behaviour. With succeeding doses, the initial period of depression of avoidance responding was shortened and the subsequent rebound stimulation disappeared.4. The results support the hypothesis that histamine in the brain is involved in several behavioural phenomena.