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Biomedical subjects

H Anisman

Publications and source records attributed to H Anisman.

At least 127 records · Page 7Linked to original sources
PubMed1985

Stimulus perseveration in a water maze following exposure to controllable and uncontrollable shock.

When placed in a water-filled maze, mice display a pronounced preference for the illuminated over the nonilluminated arm of the maze. Exposure to inescapable shock increased the time spent in the illuminated arm of the maze, and decreased the frequency of entries into the nonilluminated arm. When animals that had received shock entered the nonilluminated arm they exhibited more activity per second than nonstressed animals. Controllability over the stressor enhanced the preference for the illuminated arm; however, the contribution of this variable was dependent on the number of shock trials mice received. Following 180 escapable or inescapable shock presentations the preference for the illuminated arm was enhanced. The propensity to approach the illuminated arm declined following a greater number (360) of escapable shock trials, while the preference for the illuminated arm did not decline in mice that received inescapable shock. Both escapable and inescapable shock were also found to produce a transient disruption of discrimination performance in a task where animals were required to emit a contraprepared response (swim to dark), whereas these treatments were without effect on performance of the highly prepared response of approaching the illuminated arm. It is provisionally suggested that enhancement of the perseveration represents an innate response to stressful stimuli, but as animals learn mastery over the response contingencies, the persistence in adopting such a response strategy wanes. Moreover, despite the differential effects of escapable and inescapable shock on the perseverative tendency, discrimination accuracy may not be differentially affected by these treatments in a task where acquisition progresses quickly and where explicit cues are associated with the correct and incorrect arms of the maze.

Animals↗
PubMed1984

Prevention of stressor-induced disturbances of self-stimulation by desmethylimipramine.

Following exposure to uncontrollable footshock mice displayed a pronounced reduction of responding for electrical brain stimulation from the nucleus accumbens. In mice that received repeated treatment with the tricyclic antidepressant, desmethylimipramine, the shock induced reduction of responding was attenuated. It was suggested that, among other things, uncontrollable stressors result in disturbances of motivational/reward processes, which are antagonized by repeated treatment with desmethylimipramine.

Animals↗
PubMed1984

Effects of inescapable shock and norepinephrine depletion induced by DSP4 on escape performance.

The potential contribution of dorsal bundle norepinephrine (NE) in the induction of escape disturbances engendered by inescapable shock was evaluated following administration of the NE neurotoxin, DSP4. Treatment with DSP4 produced marked NE reductions in the hippocampus and cortex, a moderate reduction of NE in the locus coeruleus, but only small effects on hypothalamic NE. In contrast to the effect of inescapable shock, DSP4 was found not to influence escape behavior among naive mice or mice that had received inescapable shock. Moreover, DSP4 was without effect on escape performance irrespective of whether animals were individually or group housed, a treatment that has been shown to be sensitive to manipulations that influence escape performance. Treatment with DSP4 was found not to influence the escape interference ordinarily provoked by either haloperidol or alpha-MpT. Interestingly, the escape interference ordinarily engendered by the dopamine-beta-hydroxylase inhibitor, FLA-63, was eliminated among mice that had been pretreated with DSP4. The interference effect induced by inescapable shock is probably not attributable to NE alterations in the hippocampus and locus coeruleus. Serial or parallel effects of shock on more than a single transmitter system are likely to be responsible for the behavioral interference.

Amines↗
PubMed1984

Amphetamine-induced perseverative behavior in a radial arm maze following DSP4 or 6-OHDA pretreatment.

Mice permitted to explore an 8-arm radial maze tended to visit those arms least recently entered. Treatment with D-amphetamine engendered a perseverative tendency, wherein mice repeatedly visited two arms of the maze. Administration of the norepinephrine (NE) neurotoxin, N-2-chloroethyl-N-ethyl-2-bromo-benzylamine (DSP4), appreciably reduced NE in the hippocampus and cortex, moderately reduced NE in the locus coeruleus, and had only a small effect on hypothalamic NE. The DSP4 treatment resulted in a decrease of locomotor activity among amphetamine-treated mice, coupled with an increase of stereotyped response patterns. Although the NE depletion did not affect the pattern of exploration that mice ordinarily displayed, DSP4 appreciably increased the perseverative tendency provoked by amphetamine. Reduction of dopamine (DA) and NE by intraventricular administration of the catecholamine neurotoxin, 6-hydroxydopamine (6-OHDA), antagonized the effects of amphetamine, such that the frequency of alternation responses was increased and the proportion of perseverative responses was reduced. The effectiveness of the 6-OHDA treatment in antagonizing the amphetamine-induced perseveration was not reduced among mice that were pretreated with desmethylimipramine, which resulted in partial prevention of the NE reduction by 6-OHDA administration. It is suggested that DA neuronal activity contributes to the amphetamine -provoked perseveration , whereas NE stimulation modifies the perseverative tendency by influencing exploration or habituation.

Amines↗
PubMed1984

Responding for brain stimulation: stress and desmethylimipramine.

Stressors influence the activity of biogenic amines and provoke a variety of behavioral disturbances which have been considered as models of human depression. To evaluate the effects of stressors on reward processes, responding for electrical brain stimulation was assessed after acute or chronic shock, and the modification of performance by desmethylimipramine was determined. While escapable shock did not affect performance, inescapable shock reduced responding from the nucleus accumbens and medial forebrain bundle, but not from the substantia nigra. These deficits were were antagonized by repeated stressor application or by desmethylimipramine. Uncontrollable stressors may influence motivational processes subserved by some brain regions, and may thus influence affective state. Chronic stress or desmethylimipramine may induce adaptive neurochemical changes, thereby preventing the behavioral disturbances otherwise produced by stressors.

Adaptation, Psychological↗
PubMed1984

Acute and chronic stress effects on performance in a forced-swim task.

The effects of uncontrollable stressors on performance in a subsequent forced-swim paradigm were assessed in mice. Uncontrollable shock initially induced behavioral invigoration; however, within 24 h of stressor application, swimming behavior was depressed relative to nonstressed mice. The controllability of the stressor did not influence the initial invigoration, being present among escapably shocked mice as well as among mice that received (yoked) inescapable shock. In contrast, the depression of responding evident 24 h after stressor application was related to the availability of behavioral coping methods. Finally, following repeated exposure to footshock there was no indication of adaptation to the behavioral changes ordinarily induced by acute shock stress. The data were related to the effects of uncontrollable stressors on escape performance, and with respect to the use of this preparation as an animal model of human depression.

Animals↗
PubMed1984

Effects of pimozide on escape and discrimination performance in a water-escape task.

The effects of pimozide (0.2 and 0.4 mg/kg) on discrimination learning were evaluated by a water-escape paradigm in which the degree of motor difficulty was manipulated by varying water temperature. Treatment with the drug marginally affected escape latencies in relatively warm water (25 degrees C) but markedly disrupted escape latencies when the task was more demanding (e.g., 15 degrees C and 20 degrees C water). The escape deficits, however, were not accompanied by disturbances in the acquisition of a position discrimination response or of a cue discrimination response when mice were required to make the highly prepared response of swimming to light or the contraprepared response of swimming to dark. These data were taken to suggest that in tasks involving aversive motivation pimozide influences performance through its effects on response maintenance but does not appear to affect either associative or motivational processes.

Animals↗
PubMed1983

Acute and chronic amphetamine treatment: differential modification of exploratory behavior in a radial maze.

Mice permitted to explore an 8-arm radial maze displayed high levels of spontaneous alternation as measured by the frequency of visiting (a) the 4 least recently entered arms, (b) the 2 least recently visited arms, and (c) sequences of arms which are adjacent to one another. Acute treatment with low doses of amphetamine (1.0 mg/kg) eliminated the alternation tendency. Higher doses (5.0-7.0 mg/kg) also produced marked stimulus perseverance, such that mice tended to revisit the two arms that had been most recently entered. With repeated amphetamine treatment the perseverance tendency was attenuated. The abatement of perseverance in the radial maze did not appear to reflect simply the reduction in the potency of the drug. That is, the reduction of perseverance after chronic exposure to amphetamine was not accompanied by recovery of normal exploratory patterns. In fact, the alternation and adjacent alternation patterns typical of naive animals were absent in mice chronically treated with amphetamine even when tested in the nondrug state. It was suggested that the attenuation of amphetamine induced perseverance after chronic amphetamine administration may reflect a breakdown of normal behavior patterns rather than the development of a genuine tolerance.

Animals↗
PubMed1983

Attenuation of perseverative behavior after repeated amphetamine treatment: tolerance or attentional deficits?

When permitted to explore an 8-arm radial maze, animals exhibited a systematic pattern of exploration characterized by preference for the most novel arms (spontaneous alternation) and entry into immediately adjacent arms (adjacent alternation). Acute treatment with moderate dosages of amphetamine reduced the proportion of both types of alternation responses and induced marked stimulus perseverance, i.e., consecutive entries between pairs of arms. Prior exposure to the apparatus enhanced the degree of perseverance ordinarily observed, and provoked perseverance after low doses of the drug. In contrast to acute drug treatment, perseverance was reduced after chronic amphetamine administration. However, chronic amphetamine treatment did not appear simply to reduce the potency of the drug. In contrast to the effects of apparatus pre-exposure on the degree of perseverance induced by acute amphetamine treatment, the degree of perseverance was not enhanced by pre-exposure to the maze in mice with a history of chronic amphetamine administration. Moreover, the exploratory pattern evident in chronically treated animals differed from that of control animals even when tested in the nondrug state. That is, animals chronically treated with amphetamine and tested with saline exhibited alternation scores which did not deviate from chance. These data suggest that chronic amphetamine treatment alters the way in which organisms attend, or respond, to environmental stimuli.

Amphetamine↗
PubMed1983

Alteration of exploration and the response to food associated cues after treatment with pimozide.

A series of experiments assessed the effects of pimozide on spontaneous alternation in a Y- and 8-arm radial maze, and on approach to food or cues that had previously been associated with food. Mice treated with pimozide (0.2, 0.4 and 0.8 mg/kg) displayed a dose dependent reduction of alternation performance, without engendering a perseverative tendency and apparently without affecting the course of habituation. When food deprived mice entered an arm of the maze that was baited with a food pellet they consumed the food and remained in the vicinity of the food cup. Moreover, upon retesting in the non-drug state mice still exhibited a preference for cues that had been associated with food. It seems that although pimozide at the doses tested produced a haphazard pattern of exploration, the drug did not alter the rewarding value of secondary reinforcers. Contrary to an anhedonic hypothesis, it is suggested that higher doses of pimozide may actually increase, rather than decrease, the saliency of biologically significant stimuli.

Animals↗
PubMed1983

Region-specific reductions of intracranial self-stimulation after uncontrollable stress: possible effects on reward processes.

Rates of responding for intracranial self-stimulation from the medial forebrain bundle, nucleus accumbens and substantia nigra were evaluated in mice that had been exposed to either escapable shock, yoked inescapable shock or no shock treatment. Whereas performance was unaffected by escapable shock, marked reductions of responding from the medial forebrain bundle and nucleus accumbens were evident following the uncontrollable shock treatment. Responding from the substantia nigra was unaffected by the stress treatment. Uncontrollable shock is thought to reduce the rewarding value of responding for electrical brain stimulation from those brain regions in which stressors are known to influence dopamine activity.

Animals↗
PubMed1983

Alterations of exploratory patterns induced by uncontrollable shock.

A series of studies evaluated the effects of footshock on subsequent patterns of exploration in an eight-arm radial maze. When permitted to explore an eight-arm maze freely, mice typically exhibited a characteristic pattern of exploration in which they tended to enter arms of the maze that were least recently visited (spontaneous alternation). Moreover, animals frequently made successive entries into immediately adjacent arms of the maze (adjacent alternation). Following exposure to escapable shock the alternation performance is not appreciably altered; however, an identical amount of uncontrollable shock disrupted the adjacent alternation tendency. The disruption was evident immediately after shock, but was absent if mice were tested 24 hr after the inescapable-shock treatment. Interestingly, when mice were reexposed to a small number of shocks, a treatment which itself has no effect, the disturbance of adjacent alternation was reinstated. It is suggested that the alterations of exploratory patterns may be related to catecholamine alterations provoked by stressors, and that the behavioral disturbance could potentially influence performance in tasks involving associative processes.

Animals↗
PubMed1983

Cross-stressor immunization against the behavioral deficits introduced by uncontrollable shock.

Exposure to inescapable shock disrupted performance in both shock- and water-escape tasks. These deficits were prevented in mice that were previously trained in the same task. However, an asymmetrical immunization effect was seen in a cross-stressor paradigm. Whereas deficits of water-escape performance engendered by inescapable shock were prevented by prior shock-escape training, the deficits of shock-escape performance were not eliminated by prior water-escape training. Evidently, the immunization effect occurs when initial training and subsequent testing are conducted in the same task, or when the initial training and uncontrollable stress session involve the same aversive stimulus. Norepinephrine determinations revealed that reductions of the amine introduced by inescapable shock were unaffected by prior shock-escape training and were enhanced by prior exposure to the stress of water immersion. Thus, although the performance deficit introduced by inescapable shock may be related to variations of norepinephrine, the immunization effect probably was unrelated to alterations of this transmitter. Rather, the data provisionally suggested that the immunization stems from two independent factors: Namely, initially training animals in an active escape task may (a) disrupt subsequent learning that the inescapable stress actually is uncontrollable and (b) limit the influence of the motor deficits introduced by uncontrollable shock on subsequent escape performance.

Animals↗
PubMed1983

Acute exposure to pulsed microwaves affects neither pentylenetetrazol seizures in the rat nor chlordiazepoxide protection against such seizures.

Three experiments failed to provide consistent evidence for an effect of 2.70 GHz pulsed microwave radiation up to 20 mW/cm2 on pentylenetetrazol-induced seizures or on the efficacy of chlordiazepoxide for counteracting such seizures. Microwave radiation counteracted the hypothermic effects of chlordiazepoxide without altering its antiseizure efficacy. This underscores the dissociation between thermal and pharmacological effects of microwaves.

Animals↗
PubMed1982

Stimulus change influences escape performance: deficits induced by uncontrollable stress and by haloperidol.

Exposure to uncontrollable foot-shock or treatment with haloperidol was found to disrupt subsequent escape behavior. Performance among naive mice, as well as mice that had been exposed to inescapable shock or treated with haloperidol could be enhanced by either interrupting the shock train during escape testing or by presentation of a novel stimulus. The effectiveness of these treatments were dependent on the time at which the change in stimulation occurred. That is, shock interruption or cue presentation just prior to escape being possible enhanced performance, but the same manipulation several seconds prior to escape being possible had only a limited effect. In addition, the time of cue termination also influenced escape behavior. When cue offset coincided with or followed successful escape a performance enhancement was evident, but when cue offset occurred several seconds prior to escape, performance was not affected. It was suggested that inescapable shock and haloperidol treatment hinder performance by disrupting response maintenance. Shock interruption and novel cue presentation minimize disturbances of escape performance by altering the course of the decline of shock-elicited activity.

Animals↗
PubMed1982

Avoidance performance, cue and response-choice discrimination after neuroleptic treatment.

The effects of pimozide on discriminated avoidance performance in a Y-maze were evaluated in mice. Relatively low doses of pimozide (0.4 mg/kg) retarded acquisition of an active avoidance response. The avoidance deficit induced by this dosage was largely eliminated among mice that had received either 1 or 2 previous avoidance training sessions, but was still evident in mice treated with a higher drug dosage (0.8 mg/kg). If mice were initially trained in the drug condition, the disruptive effects were still evident in a later test conducted in the absence of the drug treatment. In contrast to the avoidance deficits, pimozide did not disrupt the acquisition or the performance of a cue- or response-choice discrimination. That is, once a running response was initiated (on avoidance trials) pimozide treated animals appeared capable of appropriately directing the response. It is suggested that at the dosages used pimozide did not affect S-S learning or learning response-outcome contingencies, but rather hindered performance owing to deficits in response initiation processes. Moreover, within a task involving aversive motivation pimozide did not appear to reduce the reinforcement derived for correct responding.

Animals↗