NMDA but not AMPA receptor antagonists impair the delay-interposed radial maze performance of rats

Long-term treatment of Parkinson's disease (PD) with levodopa is complicated by the development of motor fluctuations and dyskinesias. Posteroventral pallidotomy can improve tremor, bradykinesia, rigidity, and dyskinesias in PD. We performed chronic stimulation of the globus pallidus (CSGP) to duplicate the positive results of pallidotomy with reduced risk of permanent neurologic deficit in patients with advanced PD. The lead for CSGP was stereotactically implanted with the aid of microelectrode recordings in the globus pallidus pars interna. An electrical pulse generator was implanted in the subclavicular region. Stimulation settings were adjusted by computer. Five PD patients (four men, one woman) with disabling symptoms were enrolled. Three of the patients had bilateral implants. At 3 months following the last implant, four patients rated themselves as markedly improved, and one patient was moderately improved. The amount of time in the "on" state increased from 21% at baseline to 65% at 3-month follow-up (p < 0.05). There was a significant improvement in all subscales of the UPDRS (p < 0.05). One patient had an asymptomatic intracranial bleed, one patient had transient hemiparesis during surgery with stimulation, and one patient required surgical repositioning of the lead. Adverse effects caused by stimulation were minimal. CSGP is a safe and effective procedure in PD patients with motor fluctuations and dyskinesias.     

3,4 Methylenedioxymethamphetamine (ecstasy) impairs eight-arm radial maze performance and arm entry pattern in rats.

The recreational use of 3,4 methylenedioxymethamphetamine (ecstasy) in humans has been associated with memory impairment. The present study examined whether ecstasy impairs short- and long-term working memory and the pattern of arm entries in rats tested in the 8-arm radial maze with a 2-hr delay. After completing the training session, the rats were given a single dose of ecstasy (1, 2, or 3 mg/kg ip) 20 min before the test. The highest dose slightly affected short-term working memory. Under conditions of delay, there was a progressive deficit in long-term working memory, starting from I mg/kg. Under both test conditions, 2 and 3 mg/kg flattened the pattern of arm entry. None of the doses caused hyperlocomotion or stereotypy in the radial maze. These findings suggest that acute ecstasy mainly affects the long-term components of working memory and disrupts the pattern of arm entry in a way similar to serotonergic agents. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Partial hippocampal kindling affects retention but not acquisition and place but not cue tasks on the radial arm maze

The performance of rats that were partially kindled in the hippocampus was assessed on an 8-arm radial arm maze with 4 baited arms. In rats first trained and then kindled, deficits were found on a place task in which rats reached the goal arms of the maze using salient extramaze spatial cues, but not on an intramaze cue task in which rats reached the goal arms using salient intramaze cues. Acquisition of a new place task on the maze was not different between kindled and control rats. In conclusion, partial hippocampal kindling disrupted the retention but not the acquisition of a spatial or place task; retention of a nonspatial cue task was not disrupted.     

Liberal grading improves evaluations but not performance.

The effects of examination grades on 250 college students' study behaviors, attendance, and evaluations of instruction were examined in an undergraduate psychology course. A paradigm involving a team-teaching procedure was employed, which enabled the questions to be investigated in the natural setting using an experimental rather than a correlational methodology. Liberal grading was found to result in higher evaluations of course and instructor but had no demonstrable effect on studying or attendance. (10 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Within-subject decline in delayed-non-match-to-sample radial arm maze performance in aging Sprague-Dawley rats.

A within-subject design was used to examine delayed-non-match-to-sample radial arm maze performance in aging (6–18 months) male Sprague-Dawley rats. A decrease in correct choices and an increase in retroactive errors were observed at all retention intervals at 18 months of age compared with performance at 6 or 12 months. No age by retention interval interaction was observed. Neither age nor increasing retention interval influenced proactive errors during the retention test. The observation of an age- and delay-dependent increase in retroactive errors, but not proactive errors, suggests that the deficit relates to a memory dysfunction as opposed to a generalized performance deficit. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Mediodorsal thalamic lesions impair radial maze performance in the rat.

The role of the mediodorsal thalamic nucleus (MD) in spatial memory processes was assessed. Animals were preoperatively trained on an 8-arm maze placed in a visually deprived environment. Following 50 acquisition trials, one group received bilateral electrolytic lesion of the MD thalamus, whereas the other group received sham lesions. On postoperative tests of radial maze performance, MD lesioned animals made significantly more errors, made more errors sooner, and emitted fewer correct responses before making an error than did sham controls. The lesioned subjects also exhibited considerable perseveration immediately postoperation and developed response patterning on postlesion trials. Lesions of the mediodorsal thalamus may fundamentally compromise memory systems and alter ability to respond appropriately in a minimally cued environment. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Subtle but distinct impairments of rats with chemical lesions in the thalamic mediodorsal nucleus, tested in a radial arm maze.

Tested the performance of 18 hybrid BD9?×?BD10 rats trained in a radial arm maze before and after chemical lesions of the thalamic mediodorsal nucleus or the ventral tegmental area. Their behavior was compared with that of 18 sham-operated controls. Lesions were produced with ibotenic acid, a compound that selectively destroys neurons while apparently leaving fibers of passage intact. Results revealed no intergroup differences in the number of errors performed when all 6 trials were given in 1 session without interruption. The group with mediodorsal lesions, however, made significantly more errors than either of the other 2 groups when a delay of 1 hr was interposed between the 1st 4 and the last 2 trials. Furthermore, these Ss differed from Ss of the other groups in the number of sessions necessary to reach criterion, in the time needed to finish a session, and in the directness with which a goal was approached. Ss with lesions of the ventral tegmental area did not differ from Ss of the sham-operated control group in any of the measures taken. It is suggested that the deficits of rats with mediodorsal lesions resemble qualitatively those found in human patients with lesions of the mediodorsal nucleus. (63 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of US devaluation on win–stay and win–shift radial maze performance in rats.

Previous studies have shown double dissociations between win–stay and win–shift radial maze learning in terms of their underlying neural substrates. To examine the content of the associations formed in the two tasks, the authors devalued the food unconditioned stimulus (UCS) by taste aversion to differentiate stimulus–stimulus(CS–UCS) and stimulus–response (CS–CR) learning. UCS devaluation was performed in rats that were over- or undertrained on the win–stay task. Devaluation substantially reduced food consumption on the maze but failed to disrupt choice accuracy, regardless of the amount of training. Devaluation did not affect latency in overtrained rats but did increase latency in undertrained rats. In the win–shift task, devaluation caused rats to reject the reinforcer, yet they continued to accurately win–shift, but with significantly longer latencies (Experiment 3). The results suggest that an S–R association may mediate performance after extended win–stay training. In contrast, a UCS representation appears to be recalled during early win–stay and win–shift performance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Estrogen improves biochemical and neurologic outcome following traumatic brain injury in male rats, but not in females

Previous work has shown that the GABAA-receptor (GABAA-R) could be phosphorylated by cAMP-dependent protein kinase (PKA), protein kinase C (PKC), and a receptor associated kinase. However, no clear picture has yet emerged concerning the particular subunit/subtypes of the GABAA-R that were phosphorylated by PKA and PKC. In the present report we show that an antibody raised against a 23 amino acid polypeptide corresponding to a sequence in the putative intracellular loop of the beta 1 subunit of the receptor blocks the in vitro phosphorylation of the purified receptor by PKA and PKC. Moreover, N-terminal sequence analysis of the principal phosphopeptide fragment obtained after proteolysis of the receptor yielded a sequence that corresponds to the beta 3 subunit of the receptor. Such data provide additional support for our hypothesis (Browning et al., 1990, Proc. Natl. Acad. Sci. USA 87:1315-1317) that both PKA and PKC phosphorylate the beta-subunit of the GABAA-R.     

Pigeons may not use dual coding in the radial maze analog task.

Using a radial maze analog task, T. R. Zentall, J. N. Steirn, and P. Jackson-Smith (1990) found evidence that when a delay was interpolated early in a trial, pigeons coded locations retrospectively, but when the delay was interpolated late in the trial, they coded locations prospectively (support for a dual coding hypothesis). In Experiment 1 of the present study, the authors replicated the original finding of dual coding. In Experiments 2 and 3, they used a 2-alternative test procedure that does not require the assumption that pigeons' choice criterion, which changes over the course of the trial, is the same on delay and control trials. Under these conditions, the pigeons no longer showed evidence for dual coding. Instead, there was some evidence that they showed prospective coding, but a more parsimonious account of the results may be that the delay produced a relatively constant decrement in performance at all points of delay interpolation. The original finding of dual coding by Zentall et al. might have been biased by more impulsive choices early in control trials but not in delay trials and by a more stringent choice criterion late in delay trials. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Differential effects of cholinergic blockade on performance of rats in the water tank navigation task and in a radial water maze.

Tested the disruptive effect of cholinergic blockade under conditions in which either the working memory or the spatial mapping requirements of the behavioral task were emphasized. In Exp I, 13 male hooded rats were trained in an 8-arm radial water maze to asymptotic performance. When delays of 5, 10, 20, and 40 min were inserted between Choice 4 and Choice 5, incidence of errors in Choices 5–8 increased after pretrial (20 min) intraperitoneal scopolamine (0.2 mg/kg) faster than under control conditions and approached chance level with the 40-min delay. Scopolamine after Choice 4 or pretrial methylscopolamine was ineffective. In Exp II, 30 Ss were trained in a Morris water tank. Acquisition was impaired by pretrial injection (20 min) of 0.1 and 0.2 mg/kg scopolamine, but a higher dose (1.0 mg/kg) was required to impair overtrained performance. In a working memory version of the navigation task, scopolamine administered 20 min before the 1st trial deteriorated retention tested 40 min later at a dose of 1.0 but not at 0.4 and 0.2 mg/kg. It is concluded that the disruptive effect of scopolamine is proportional to the demands on the working memory component of the task, whereas the use of an overtrained mapping strategy is relatively resistant to cholinergic blockade. (35 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Spatial disorientation blocks reliable goal location on a plus maze but does not prevent goal location in the Morris maze.

Cue control in spatial learning was investigated in a plus maze and a Morris maze. Rats transported in opaque containers with prior rotation to a plus maze, but not a Morris maze, could not find a goal defined by external cues. Rats transported in clear containers without rotation found the goal in both mazes. In the Morris maze, goal location was readily relearned following cue removal by rats in clear containers but not by rats in the opaque/rotation group. B. L. McNaughton et al's (1996) theory that during spatial learning sensory information is bound to preconfigured internal maps in the hippocampus, whose metric is self-notion and whose orientation depends on input from an inertial based head direction system, may explain this study's findings. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of intrahippocampal administration of colchicine on incentive contrast and on radial maze performance.

Examined the behavior of rats given intradentate injections of colchicine (COL). In Exp 1, COL-treated, artificial cerebrospinal fluid (CSF)-treated, and untreated Ss did not differ in the intake of 32% and 4% sucrose solutions, nor did they differ in degree of successive negative contrast when the 32% solution was changed to 4% sucrose. In Exp 2, the COL-treated and CSF-treated Ss did not differ in degree of suppression in the intake of a 0.15% saccharin solution when it preceded 32% sucrose in once-daily pairings (anticipatory contrast), nor did they differ in reversal performance when saccharin–sucrose and saccharin–saccharin pairings were reversed. In Exp 3, the COL-treated Ss were substantially impaired in radial-arm maze performance compared with CSF-treated controls. Results suggest that a completely functioning hippocampus is not necessary for the memory of reward quality, the comparison of rewards, the suppression of behavior when reward is decreased, the formation of associations between 2 levels of reward, and the reversal of this association, as long as these processes are reflected in consummatory behavior. Data are interpreted in terms of differences between instrumental behavior and sensory memory and/or consummatory behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Foraging experience affects gerbils' (Meriones unguiculatus) radial arm maze performance.

Tested D. S. Olton's (1978) hypothesis that the gerbil's ability to easily learn the radial maze task is due to a natural "win-shift" foraging strategy, a tendency to avoid recently visited food sites. 25 Mongolian gerbils at weaning were put in 1 of 2 environments—one in which the source of food and water was always located in the same place and the other in which the source changed location from day to day—until they were 60 days of age. They then were tested in a 17-arm radial maze. Ss reared in the environment with variable locations of food and water learned the maze task more quickly than Ss reared in the other environment. Results are consistent with Olton's hypothesis. (10 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Acute ventilatory failure in Lambert-Eaton myasthenic syndrome and its response to 3,4-diaminopyridine

Respiratory failure is a common manifestation of myasthenia gravis but is infrequent in Lambert-Eaton myasthenic syndrome (LEMS), where it is often related to the use of paralytic agents or intercurrent pulmonary pathology. Therapies that are effective acutely in myasthenia gravis are usually of minimal benefit in LEMS. We describe a patient with respiratory failure secondary to LEMS who responded to 3,4-diaminopyridine and review the 12 previously reported cases of ventilatory failure in LEMS.     

Spatial memory in pigeons on the radial maze.

A series of 7 experiments with 10 pigeons showed, contrary to recent suggestions that pigeons show little or no spatial memory on the radial maze, highly accurate performance by Ss on an 8-arm radial maze. In Exp I, Ss were trained on successive phases that raised the number of alleys to be remembered from 1 to 4. In Exp II, Ss were allowed to search the maze for food with all 8 arms open. Measures of spatial memory showed that Ss performed at a level equivalent to that found with rats in previous research by A. B. Bond et al (see record 1982-25052-001). In Exp III, testing with massed trials revealed proactive interference. Ss were able to form reference memory for subsets of baited and unbaited alleys in Exp VI. In Exp VII, Ss learned about quantities of food associated with 4 different alleys and ordered their alley choices from the largest to the smallest reward. Contrary to the previous findings with rats, Ss in Exp IV showed forgetting over retention intervals of 0–360 sec between forced and free choices. It is concluded that spatial memory in pigeons generally shows the same properties as that in rats. (49 ref) (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Dextromethorphan potentiates morphine antinociception, but does not reverse tolerance in rats

The N-methyl-D-aspartate (NMDA) and cholecystokinin (CCK)-B receptors may have a role in the development and reversal of tolerance to morphine. In morphine-tolerant rats, addition of the CCK-B receptors antagonist CI 988 or the NMDA receptor blocker dextromethorphan enhanced the antinociceptive effect of morphine on the hot plate test. However, combined administration of CI 988 and dextromethorphan did not further potentiate the antinociceptive effect of morphine in tolerant rats. Dextromethorphan by itself had no effect in tolerant rats. In drug-naive rats, dextromethorphan by itself had no antinociceptive effect, but when combined with morphine or morphine and CI 988, it significantly potentiated the magnitude and duration of the effect of morphine. Thus, unlike the reversal of tolerance with CI 988 at doses that did not potentiate the effect of morphine, the antinociception observed with the NMDA antagonist in the presence of morphine in tolerant rats may not represent the reversal of tolerance, but may instead reflect the potentiation of morphine's analgesic effect by dextromethorphan.     

Early social deprivation disrupts attentional, but not affective, shifts in rats.

This study examined the effects of early social deprivation in rats in 2 dissociable forms of inhibitory control of behavior that operate at 2 different levels of response selection: reversing the assignment of stimulus–reward associations within perceptual dimensions (affective shifts) and switching selective attention from 1 perceptual dimension to another (attentional shifts). Isolated Ss (isolates) and social controls (socials) were individually trained to spatial and nonspatial visual discrimination criteria on a radial arm maze. Whereas isolates and socials differed in neither acquisition nor reversal of both versions of the task, isolates were selectively impaired in shifting from spatial to nonspatial discrimination and vice versa. These findings demonstrate that isolation rearing selectively disrupts inhibitory control in attentional selection but leaves inhibitory control in affective processing intact. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Taste avoidance, but not aversion, learning in rats lacking gustatory cortex.

Control rats rapidly learned to avoid drinking either a sucrose solution (Exp 1) or an NaCl solution (Exp 2) when the taste was paired with illness. These rats also produced aversive reactivity to each of these solutions in a taste reactivity test. Rats that lacked gustatory cortex (GC) learned to avoid drinking sucrose and NaCl, albeit at a slower rate than control rats. GC rats failed to display aversive reactivity to these tastes. The GC rats did show normal aversive reactivity to a strong quinine HCl solution during additional tests. It is suggested that the avoidance developed by GC rats did not entail a palatability shift of the conditional stimulus as it did in control rats. This altered learning strategy may account for the consistent learning deficits found in GC rats trained to avoid tastes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)