The effect of selective MAO inhibitors on the conditioned avoidance response of Wistar rats

Behavioral and biochemical effects of 1-deprenyl and clorgyline were studied in Wistar rats. Behavioral performances was tested in a one-way and in a two-way avoidance system. The two MAO inhibitors were given acutely (1 and 10 mg/kg sc) anc chronically (1 mg/kg sc/daily, for 7 days), and their influences on learning and retention performance was tested 24 hr after the last injection. Behavioral reactions remained unchanged after acute administration of the inhibitors, while they were significantly improved following the chronic treatments, either in the one-way or in the two-way experimental situation. Biochemical analysis indicated dissociation between the influence on striatal dopamine content and the behavioral effects of 1-deprenyl and clorgyline.     

Effects of risperidone on conditioned avoidance responding in male mice

The effects of risperidone (0.1, 0.5 and 1 mg/kg) on active avoidance behaviour of BALB/C mice were explored in three acquisition sessions and in one subsequent performance session. In the acquisition phase, risperidone-treated animals showed a decrease in avoidances and in crossings in the adaptation period and in the intertrial intervals (ITIs), and an increase in non-responses; intermediate and high doses also decreased defecation. In the performance phase, 0.5 and 1 mg/kg risperidone decreased avoidance responses, crossings in the adaptation period and ITI crossing, which also decreased with 0.1 mg/kg. Moreover, 0.5 mg/kg of risperidone increased escape responses and 1 mg/kg increased non-responses and decreased defecation. The results show that risperidone has similar effects to other neuroleptics in the avoidance paradigm.     

Effects of Pavlovian conditioned stimulus-unconditioned stimulus pairings during avoidance response-prevention trials in rats.

Response prevention (blocking) has been shown to hasten extinction of an instrumental avoidance response. One interpretation suggests that the facilitation effect is mediated by Pavlovian fear reduction during conditioned stimulus exposure on blocked trials. To test the fear-reduction hypothesis 30 male Holtzman albino rats received either a typical blocking treatment, blocking with shock, or extinction alone. Results indicate that blocking with the UCS was as effective as regular blocking in facilitating extinction of avoidance. An ancillary part of the experiment to assess the effectiveness of response prevention in 30 immature Ss showed that blocking did not facilitate extinction with the weanlings. Findings suggest that facilitated extinction is not solely attributable to Pavlovian fear reduction. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Acquisition of conditioned avoidance responses by hypophysectomized rats.

Maintained hypophysectomized and sham-operated male Wistar rats on a complete high-carbohydrate dietary supplement in addition to ordinary diet to insure a state of good health. Groups so maintained were compared with respect to their ability to acquire the conditioned 2-way avoidance response 2, 3, and 5 wk. after operation. Sham-operated and hypophysectomized Ss both acquired the response with no significant differences. Almost all groups, however, included Ss which did not acquire the response. Hypophysectomized groups contained fewer of these Ss. Examination of a sample from a normal unoperated Wistar population without dietary supplement showed a proportion of Ss which did not acquire the response similar to that found with the sham-operated Ss. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effects of reserpine on the acquisition of the conditioned avoidance response.

"Six Macacus cynomolgus monkeys were trained in a shock-avoidance situation while under the influence of reserpine. Three sessions of 60 trials were given a week apart. Subsequent acquisition of the habit was retarded." (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of adrenocorticotropic hormone on conditioned avoidance in rats interpreted as state-dependent learning.

140 male Charles River CD rats were given 1 training trial that was followed 2 days later by 1 test trial in a "step-out" passive avoidance task. Each S was injected with either ACTH or placebo before training and before testing. 4 groups of Ss were used, representing the 4 possible training-testing injection combinations: placebo-placebo, placebo-ACTH, ACTH-placebo, and ACTH-ACTH. ACTH given in testing increased avoidance for subjects that had received ACTH in training and decreased avoidance for those that had received placebo in training. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of posttraining damage to the pedunculopontine tegmental nucleus on conditioned stimulus transfer in two-way active avoidance in rats.

The effects of posttraining excitotoxic lesions of the pedunculopontine tegmental nucleus (PPTg) on two-way active avoidance after changing the conditioned stimulus (CS) used during prelesion training were examined. Prelesion training was carried out with either a tone or a light as the CS, and this CS was changed during postlesion training. Replacing the tone with a light reduced the performance of control and lesioned rats, but the degree of reduction was higher in the latter. Replacing the light with a tone had slight detrimental effects in lesioned rats but not in controls. Thus, posttraining PPTg lesions slowed down the reacquisition of shuttle-box avoidance under conditions of CS transfer, an effect that may be attributable to disruption of attention and/or gating of sensory stimuli. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Phenytoin blocks the reversal of a classically conditioned discriminative eyeblink response in rabbits

The aim of the present study was to assess the role of vascular alpha 1D-adrenoceptors in the sympathetic vasopressor response in vivo. Specifically, we evaluated the effect of a selective alpha 1D-adrenoceptor antagonist, BMY 7378 (8-(2-(4-(2-methoxyphenyl)-1-piperazinyl)ethyl)-8-azaspiro(4,5)dec ane-7,9- dione 2HCl), on the vasopressor response induced by preganglionic (T7-T9) sympathetic stimulation in the pithed rat. The vasopressor response was dose-dependently sensitive to inhibition by intravenous BMY 7378 (0.1, 0.31, 1 and 3.1 mg/kg), doses of 1 and 3.1 mg/kg being equally effective. Like BMY 7378, 5-methylurapidil (0.1, 0.31, 1 and 3.1 mg/kg) antagonized the vasopressor response to spinal stimulation; doses of 1 and 3.1 mg/kg were also equally effective. In combination experiments, BMY 7378 (1 mg/kg, i.v.) and the alpha 1A-adrenoceptor antagonist, 5-methylurapidil (1 mg/kg, i.v.), showed an additive effect. The present results demonstrate that the alpha 1D-adrenoceptor subtype plays an important role in the pressor response to sympathetic nerve stimulation in the pithed rat, and confirm the participation of the alpha 1A-adrenoceptor subtype in the same response.     

Effect of tetramethylpyrazine on reserpine-induced gastric lesion in rats

The present study was undertaken to determine the effect of tetramethylpyrazine administered intraperitoneally on gastric lesions, gastric acid secretion, gastric barrier mucus secretion, and gastric contraction in reserpine-treated rats. The results of this study demonstrated that tetramethylpyrazine at doses of 0.5, 1, 10, and 20 mg/kg significantly inhibited the formation of gastric lesions induced by reserpine, with suppressive rates of 57.5%, 64.0%, 94.1%, and 96.0%, respectively. Tetramethylpyrazine (1 and 20 mg/kg) significantly prompted the secretion of gastric barrier mucus but had no effect on the secretion of gastric acid. Our findings also showed that tetramethylpyrazine (1 and 20 mg/kg) significantly suppressed the frequency of gastric contractions, but had no effect on the amplitude of gastric contraction. These results indicate that the protection of tetramethylpyrazine results, in part, from promoting gastric barrier mucus secretion and suppressing the frequency of gastric contraction, but not from suppressing the secretion of gastric acid and the amplitude of gastric contraction.     

Conditioned nausea in rats: Assessment by conditioned disgust reactions, rather than conditioned taste avoidance.

The terms conditioned taste avoidance and conditioned taste aversion are often used interchangeably in the literature; however, considerable evidence indicates that they may represent different processes. Conditioned taste avoidance is measured by the amount that a rat drinks in a consumption test that includes both appetitive phases and consummatory phases of responding. However, conditioned taste aversion is more directly assessed using the taste reactivity (TR) test that includes only the consummatory phase of responding. Rats display a conditioned taste aversion as conditioned disgust reactions (gapes, chin rubs, and paw treads) during an intraoral infusion of a nausea-paired flavored solution. Only treatments that produce nausea produce conditioned disgust reactions, but even rewarding drugs produce conditioned taste avoidance. Furthermore, treatments that alleviate nausea prevent the establishment and the expression of conditioned disgust reactions, but they do not necessarily modify conditioned taste avoidance. Considerable evidence exists indicating that these two measures can be independent of one another. The potential of a compound to produce conditioned disgust reactions is a reflection of its nausea-inducing properties. Taste avoidance may be motivated by conditioned fear rather than conditioned nausea, but conditioned disgust is motivated by conditioned nausea. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Ontogeny of eyeblink conditioned response timing in rats.

Eyeblink conditioned response (CR) timing was assessed in adult and infant rats. In Experiment 1, adult rats were trained with a 150-ms tone conditioned stimulus (CS) paired with a periorbital shock unconditioned stimulus (US; presented at 200- or 500-ms interstimulus intervals [ISIs]). The rats acquired CRs with 2 distinct peaks that occurred just before the US onset times. Experiments 2 and 3 examined developmental changes in CR timing in pups trained on Postnatal Days 24-26 or 32-34. Experiment 3 used a delay conditioning procedure in which the tone CS continued throughout the ISIs. Pups of both ages exhibited robust conditioning. However, there were age-related increases in the percentage of double-peaked CRs and in CR timing precision. Ontogenetic changes in eyeblink CR timing may be related to developmental changes in cerebellar cortical or hippocampal function. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Pavlovian extinction in rats during avoidance response prevention.

Attempted to determine whether extinction of the aversive properties of a CS occurs during avoidance response prevention. 48 naive male albino Sprague-Dawley rats served as Ss. The CS remained somewhat aversive even after 5 5-min unreinforced presentations during response prevention, but it was significantly less aversive for Ss exposed to it without reinforcement than for nonblocked Ss or for blocked Ss given unreinforced exposures to the shock compartment in the absence of a CS. This finding supports analyses which assign a contributory role to Pavlovian extinction of CS aversiveness in facilitating avoidance extinction by response prevention. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Apomorphine-induced hypoattention in rats and reversal of the choice performance impairment by aniracetam

Intense electrical stimulation of meridian points in the rat inhibits the nociceptive tail withdrawal reflex. The objective of the present study was to determine whether spinal opioid receptors mediate this inhibition. Electrical stimulation was applied with 2 ms square pulses, at 4 Hz for 20 min at 20 times the threshold, to previously defined meridian points in the hindlimb. Threshold was the minimum current required to elicit muscle twitch. In lightly anaesthetized intact rats (n = 8) stimulation inhibited tail withdrawal during and for greater than one hour after the end of stimulation. In unanaesthetized spinal rats (n = 12) this inhibition was less and the post-stimulation effect lasted for 15 min. In control anaesthetized intact (n = 28) and unanaesthetized spinal rats (n = 14) placement of electrodes without stimulation had no effect. In spinal rats, preadministration of naloxone (25 mg/kg, i.p.) blocked the evoked inhibition (n = 11). In intact animals both naloxone (n = 8) and the mu-opioid receptor antagonist, beta-funaltrexamine (10 nmol; n = 9), given via a chronic intrathecal catheter, attenuated inhibitions during and after the end of stimulation by 50-60%. The delta-opioid receptor antagonist H-Tyr-tic psi[CH2NH]Phe-Phe-OH (TIPP[psi]; 10 nmol; n = 7) and the kappa-opioid receptor antagonist nor-binaltorphimine (10 nmol; n = 13) given by lumbar puncture attenuated the inhibition during the stimulation by 30% and 56%, respectively; both antagonists blocked the post-stimulation effect and even facilitated the withdrawal. The data suggest that spinal mu-, delta- and kappa-opioid receptors each contribute to the evoked inhibition.     

Counterconditioning versus forced exposure in extinction of avoidance responding and conditioned fear in rats.

Conducted 2 experiments using 64 and 32 male Long-Evans hooded rats, respectively. Exp. I investigated the extinction of the conditioned avoidance response (CAR) by response prevention and counterconditioning methods. Response prevention was most effective in extinguishing both the CAR and associated conditioned fear, although counterconditioning produced greater extinction than the regular extinction procedure. Exp. II equated the counterconditioning and response-prevention conditions for duration of CS exposure and demonstrated the superiority of the latter in extinguishing the CAR; both methods were equally effective in decreasing conditioned fear as compared to the regular extinction procedure. Extinction of the CAR was facilitated to the extent to which different procedures eliminated response-contingent feedback by reducing escape-avoidance responses. Conditioned fear was a function of the amount of nonreinforced exposure to the CS during extinction. (24 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of early postnatal AF64A treatment on passive avoidance response and radial maze learning in rats

In order to investigate how the selectively lesioned cholinergic system at the early postnatal age influences adult learning behavior, the effects of postnatal administration of ethylcholine mustard aziridinium ion (AF64A), a selective cholinergic neurotoxin, on the acquisition of 2 kinds of learning tasks were examined. Rat pups received an intraventricular injection of AF64A (1.0 or 2.0 nmol) or saline on postnatal day 8, and in adulthood (at 3 months of age), they were tested with the acquisition of passive avoidance response (PAR) and 8-arm radial maze learning. In PAR testing, a significant impairment was observed in male AF64A-treated rats. In addition, in the radial maze task, AF64A-treated rats needed significantly more trials to acquire the task as compared with saline-treated animals. Histological examination after behavioral testings revealed a marked reduction of acetylcholinesterase-stained fibers in the hippocampus and dentate gyrus of the AF64A-treated groups, while there were no detectable changes in the striatum or cerebral cortex. The results suggest that early postnatal AF64A administration induced learning deficits in adulthood which were associated with long-lasting cholinergic denervation in hippocampal formation.     

Latent timing in human conditioned avoidance.

Four experiments explored signal timing in human conditioned avoidance. Participants received discrimination training with different duration signals that announced the outcome (S+) or not (S-). Temporal discrimination and superposition of performance to S+ signals of different length (3, 6, or 9 s) was found both in within-subjects (Experiment 1a) and between-subjects (Experiment 1b) designs. S- signals also produced a temporal discrimination and superposition effect during a single test trial conducted after the meaning of the signals was reversed through instructions. Experiments 2a and 2b replicated these results in a situation in which (a) the durations of the S+ and S- signals were different (4.5 or 9 s) to prevent any temporal generalization between them (Experiment 2a), and (b) only S- signals were presented during training, precluding developing of inhibition to S- (Experiment 2b). These results show that participants time both S+ and S- signals in human conditioned avoidance, and they further suggest that the timing of a cue is independent of reinforcement. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Differential effects of dopamine and AMPA receptor antagonists on the expression of conditioned avoidance responding in rats.

AMPA receptor antagonists disrupt avoidance responding, but their day-to-day effect on this behavior has not been elucidated. This study compared the multisession effect of the AMPA/kainate receptor antagonist CNQX with that of the typical antipsychotic haloperidol on the expression of avoidance responding. Rats (N = 199) were trained to move to safety on presentation of a tone in one-way active conditioned avoidance and were tested across 5 sessions. Intracerebroventricular (icv) injection of CNQX (20-min injection-test interval) produced a dose-dependent, immediate block of avoidance responding, compared with the extinction-like decline of avoidance responding produced by haloperidol (intraperitoneal [ip], 60-min injection-test interval; icv, 60 but not 20-min injection-test interval). Previous exposure to CNQX significantly reduced its efficacy, illustrating that its effects may not be specific to the conditioned safety-related stimuli that control responding in conditioned avoidance, as proposed for antidopaminergic compounds. The new multisession profile of disrupted avoidance responding illustrated by CNQX suggests different roles for glutamatergic and dopaminergic neurotransmission in conditioned avoidance responding. Results are consistent with a role for AMPA receptors in maintaining the expression of learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of ventromedial hypothalamic lesions on conditioned sucrose aversions in rats.

Maintained 11 female Wistar rats with lesions of the ventromedial hypothalamus (VMH) at 95% body weight (BW) and gave them an intraperitoneal injection of a 2% BW dose of .15 M lithium chloride following the consumption of sucrose pellets. Control groups (N = 18) maintained at 95 and 80% BW received the same treatment. The VMH and 80% groups showed less aversion to sucrose than the 95% group. Results suggest that appetitive passive-avoidance deficits in VMH-lesioned rats may be produced by increased hunger motivation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)