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Query: UMLS:C0020672 (hypothermia)
 17,327 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Two experiments examined the extent to which retrograde amnesia (RA) is attenuated by prior learning experiences. In Experiment 1, rats initially received either passive avoidance training in a step-through apparatus, exposure to the apparatus, or noncontingent footshock. When training on a second but different passive avoidance task was followed by hypothermia treatment, RA was obtained only in the latter two groups. In Experiment 2, one-way active avoidance training, yoked noncontingent shocks, or apparatus exposure constituted the initial experience. Subsequent step-down passive avoidance training and amnestic treatment resulted in memory loss for the prior apparatus exposure group, but not for either of the preshocked conditions. These experiments demonstrate that certain types of prior aversive experience can substantially modify the magnitude of RA, and, in conjunction with other familiarization studies, emphasize a paradox for interpretations of RA based solely upon CNS disruption. The possibility that hypothermia treatment serves as an important contextual or encoding cue necessary for memory retrieval was considered. It was suggested that prior experience may block RA by enabling rats to differentiate training and treatment conditions.
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PMID:Effects of prior aversive experience upon retrograde amnesia induced by hypothermia. 123 6

The present investigation assessed whether increased congruency between ACTH state present shortly after training and that at testing contributed to memory recovery. If recovery were related to an increased correspondence between internal state present after training and that at testing, then suppressing ACTH release should block memory recovery. This was the hypothesis that was examined in the present investigation. Specifically, animals were trained on a passive avoidance task, administered hypothermia (the amnestic agent) and, shortly prior to testing, given treatments known to be effective in reversing memory loss induced by hypothermia. Before training (Experiment 1) or testing (Experiment 2) animals were injected with either dexamethasone (an agent that suppresses ACTH release) or saline. Results, in general, indicated that when ACTH release was suppressed, a blunted recovery effect was obtained. This reduction in the extent of memory recovery was observed when ACTH was suppressed either at training or at testing. These data are interpreted as providing support for an ACTH-related, state-dependent retention mechanism contributing to recovery from hypothermia-induced retrograde amnesia in rats.
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PMID:Role of ACTH in recovery from retrograde amnesia induced by hypothermia in rats. 255 75

Reminder (Experiment 1) and familiarization (Experiment 2) treatments were found to have similar effects on the 24-hr retention performance of 24- to 26- and 90- to 100-day-old rats that either did or did not undergo an amnesic treatment (hypothermia) immediately after training. Similar degrees of retrograde amnesia and normal forgetting were evident in both trained age groups that were not subjected to familiarization or reminder treatments. These results suggest that memory processes in weanling and adult rats are similar in susceptibility to disruption by an established amnesic treatment (hypothermia) and in the ease of prevention of and recovery from amnesia by recognized preventive (familiarization) and alleviation (reminder) measures. The similarity of the effects of these preventive and alleviation treatments on normal forgetting and induced amnesia suggests that experimentally induced amnesia may be a fruitful approach to studying the ontogeny of memory processes and, more specifically, to studying factors that influence infantile amnesia.
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PMID:Preventing and alleviating hypothermia-induced amnesia in weanling and young adult rats. 261 Sep 12

Young rats (16-30 days), trained on a one-trial passive avoidance task, were subsequently submitted to the amnesic agent hypothermia 0, 5, 10, 20 or 30 min later, and tested for retention 6 h after training. While hypothermia administered 10 min after training was no longer effective in 30-day rats, it still induced a significant retrograde amnesia in younger animals. In 16- and 18-day rats, administration of hypothermia 20 min after training could still produce a slight but statistically non-significant amnesia. Additionally, exposition to a reinstatement treatment was found to alleviate the amnesic effects of hypothermia in 20- and 30-day-old animals, while it seemed ineffective in 16- and 18-day rats. These findings suggest that the more immature the animal, the longer the consolidation period, the more vulnerable the mnemonic trace, and the less effective a reinstatement treatment for alleviation of retrograde amnesia.
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PMID:Passive avoidance memory consolidation and reinstatement in the young rat. 339 38

Although there have been several reports that preweanling rats and mice are relatively resistant to experimentally induced retrograde amnesia, there is virtually no information concerning susceptibility to anterograde amnesia in subjects of this age. Therefore, in the present experiment, 23-day-old rats received hypothermia either prior to, or immediately after, punishment training in an attempt to induce anterograde and retrograde amnesia, respectively. When tested 24 hr later, only those subjects given hypothermia prior to training exhibited any loss of retention. Thus these results confirmed previous evidence of resistance to retrograde amnesia in preweanling rats and further demonstrated that substantial anterograde amnesia could be obtained in these subjects. Performance of subjects tested after a 5-min retention interval revealed that the poor retention performance in subjects cooled prior to training and tested 24 hr later was not due to a learning deficit. These results are also discussed with respect to the issue of the independence of anterograde and retrograde amnesia.
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PMID:Differential susceptibility to anterograde and retrograde amnesia treatments in preweanling rats. 367 43

In contrast with the extensive animal research on retrograde amnesia, relatively little attention has been given to anterograde amnesia. Moreover, previous studies of anterograde amnesia have not always clearly separated the effects of the anterograde treatment on acquisition from those on retention. Thus, hypothermia-induced anterograde amnesia for a one-trial conditioned fear memory was examined in three experiments. Experiment 1A demonstrated an anterograde disruption of performance in subjects receiving training in the hypothermic state (29 degrees C) and tested 24 hr later. Acquisition of the target memory in animals exposed to hypothermia prior to conditioning was demonstrated in Experiment 1B. Subjects conditioned while in a hypothermic state (29 degrees C) performed similarly to noncooled subjects if tested shortly after conditioning (while still in a hypothermic state), but not 24 hr after conditioning (while in a normothermic state). Experiment 2 shows that the anterograde amnesia effect is temperature dependent. That is, of animals trained at 29 or 33 degrees C, only the more hypothermic group demonstrated deficits in retention when tested 24 hr later. This experiment also attempted, unsuccessfully, to demonstrate recovery of the amnestic memory by administration of a noncontingent footshock prior to testing. Implications of the failure to demonstrate recovery of memory are discussed along with possible mechanisms involved in producing anterograde amnesia.
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PMID:Anterograde memory loss induced by hypothermia in rats. 688 43

A nonbarbiturate anesthetic consisting of ketamine HCl (Ketaset) and xlyazine (Rompun) was administered to assess the effects of anesthesia on hypothermia-induced retrograde amnesia in Long Evans hooded and Sprague-Dawley albino rats. Results from Experiment 1a indicate that this anesthetic does not attenuate retrograde amnesia, and the findings from Experiment 1b suggest that awakening from Ketaset/Rompun anesthesia at normal body temperature (following administration of deep body cooling) does not attenuate the resulting hypothermia-induced retrograde amnesia. Experiment 2 demonstrated that various delays between training and hypothermia resulted in a temporal gradient that was the same for animals cooled while either conscious or under anesthesia. The results of Experiment 3 showed that rats made amnesic while under anesthesia did not recover the target memory if given a recooling treatment, but rats that were made amnesic while conscious did recover the memory with the same reminder treatment. These findings indicate that the conscious processing of stimuli associated with hypothermia treatment is not necessary in inducing hypothermia-induced retrograde amnesia, but that conscious processing is an important factor if the amnesia is to be recovered with a recooling treatment.
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PMID:Differential effects of Ketaset/Rompun anesthesia on hypothermia-induced retrograde amnesia and its recovery. 856 78

In studies of experimentally induced retrograde amnesia (RA), as the interval between training and the amnestic treatment is lengthened, amnesia decreases (4). This temporal gradient for RA has been reported with a wide variety of amnestic agents, including RA produced by thermoregulatory disturbances (8). This temporal gradient for RA is not unlike certain characteristics of classical conditioning, where weaker conditioned responding occurs when the interval between the conditioned stimulus (CS) and unconditioned stimulus (US) is lengthened. Furthermore, there is evidence that administration of anesthetics can lengthen the "effective conditioning" interval between the CS and US, as demonstrated in a conditioned taste-aversion (CTA) procedure (10). In that study, little conditioning was observed when a 3-h delay (or more) was incorporated between presentations of the CS (flavor) and the US (toxin). However, if subjects were anesthetized immediately after the CS was delivered and remained anesthetized during the CS-US interval, strong conditioning was observed with CS-US intervals of up to 9 h. The aim of the present experiment was to determine if the temporal gradient for hypothermia-induced RA could also be lengthened. That is, we tested whether the interval between training and hypothermia treatment could be lengthened by anesthetizing subjects with Ketaset-Rompun. The results indicate that the training-to-amnestic agent interval could be lengthened within moderate limits. The implications for hypothermia-induced RA is further discussed.
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PMID:Ketaset-Rompun extends the temporal gradient for hypothermia-induced retrograde amnesia. 1040

Malignant neoplasms rarely extend into the inferior vena cava and up to the right side of the heart. Although massive pulmonary tumor embolism occurs relatively rarely, it can be a catastrophic problem. Intraoperative pulmonary tumor embolism and cardiac arrest occurred in a 68-year-old woman while dissecting the inferior vena cava to resect a pararenal tumor extending into the retrohepatic inferior vena cava. Abrupt arterial hypotension, tachycardia, and increased central venous pressure lead to the diagnosis of massive pulmonary tumor embolism. Emergency cardiopulmonary bypass was commenced under profound hypothermia and cardiac arrest. The tumors in the main pulmonary artery were extracted, and fragments of remnant tumor were retrieved by a vascular endoscope, a Fogarty catheter, and milking of the lung. Following embolectomy, the tumor in the retrohepatic to infrarenal inferior vena cava was removed and the primary tumor together with the infrarenal inferior vena cava was resected under hepatic vascular exclusion and partial cardiopulmonary bypass. The inferior vena cava below the renal veins was not reconstructed. The patient recovered with slight retrograde amnesia. A postoperative pulmonary perfusion scintigram showed no defect in the pulmonary circulation. She is well now 8 months after surgery. Safe prevention measures should be accomplished as a part of the perioperative management of patients with inferior vena cava tumor thrombus that may be fragile, and cardiopulmonary bypass should always be stand-by on surgery.
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PMID:Intraoperative massive pulmonary tumor embolism from clear cell sarcoma in the retroperitoneum: successful treatment using cardiopulmonary bypass. 1523 30

Two experiments were conducted using rats to determine whether extinction is susceptible to a traditional amnestic agent (i.e., hypothermia) and to examine whether amnesia for extinction follows the same characteristics as those that occur with original memories. In Experiment 1, rats received hypothermia immediately, 60 min, or 120 min after extinction. When tested, the subjects cooled shortly after extinction showed little memory of the extinction training. This amnesia for extinction disappeared with longer postextinction delays, demonstrating a temporal gradient. Experiment 2 replicated the basic finding and demonstrated that an amnestic-extinguished memory could be recovered by reexposing the subjects to the amnestic agent and that the recovered extinction memory did not persist. These findings provide more evidence that extinction is a form of new learning and are consistent with retrograde amnesia research for original memories showing a temporal gradient and alleviation of retrograde amnesia by reexposure to the amnestic agent.
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PMID:Retrograde amnesia for extinction: similarities with amnesia for original acquisition memories. 1791 18


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