Stimulus control of shuttle avoidance in young and adult rats.

Investigated stimulus generalization of 2-way active avoidance behavior in young and adult rats. In Exp. I with 12 adult and 12 young male Holtzman albino rats, CS frequency gained marked and comparable control over responding in both age groups; variation of background frequency prior to a no-tone CS, however, failed to exert any substantial control over avoidance behavior in either age group. In Exp. II with 12 Ss, Pavlovian frequency discrimination training was interpolated between acquisition of the shuttle response and generalization testing. Relative to their respective single stimulus control groups, the adult Ss showed a reliable peak shift in modal responding and the young Ss revealed a distortion in the gradient at frequency values on the side of CS+, opposite that of CS-. Although the occurrence of a peak shift was somewhat surprising in light of the fact that CS- here served as a "safety" signal, the data are interpreted as consistent with explanations of discrimination learning based upon the summation of excitatory and inhibitory gradients. In general, both experiments suggest that variations of CS frequency in an active avoidance situation tends to result in similar gradients for both young and adult Ss. The disparity between the present and previous findings are discussed in terms of the response requirements of the test situation. (French summary) (23 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of hippocampal microinjections of d-amphetamine and scopolamine on active avoidance behavior in rats.

100 male Sprague-Dawley rats received bilateral injections of 20 or 40 mg of dextroamphetamine or scopolamine into the dorsal or ventral hippocampus prior to each of 8 daily training sessions in a discriminated Y-maze active avoidance task. Scopolamine, but not dextroamphetamine, facilitated avoidance responding in both sites, with the effect being greatest following administration of 20 mg into the dorsal hippocampus. On Days 9 and 10, all Ss received saline injections and were tested for transfer of responding to the nondrug state. A decrement of performance occurred irrespective of whether the drug had facilitated avoidance responding. The performance changes were greater following termination of scopolamine than dextroamphetamine injections, and in no case were so great as those previously reported following peripheral injections of the drugs. (53 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of varying active/passive shock levels in shuttle box avoidance in rats.

Ran 60 male Sprague-Dawley albino rats in a shuttle box with 3 levels of shock intensity-high (H), medium (M), and low (L)-which varied independently on each side. This yielded 6 groups defined by the shock level in the 2 chambers: H-H, M-M, L-L, H-L, H-M, M-L. Results indicate that when active shock level was held constant, avoidance behavior was a function of passive shock level, with lower passive shock level producing higher levels of avoidance. Avoidance was not a function of active shock level when passive shock level was held constant. 10 controls were run using a unidirectional paradigm, and avoidance was not found to be a function of the active shock level. Results are interpreted as emphasizing the role of passive avoidance in bidirectional shuttling. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Posttraining intracranial self-stimulation ameliorates the detrimental effects of parafascicular thalamic lesions on active avoidance in young and aged rats.

To evaluate whether intracranial self-stimulation (SS) ameliorates conditioning deficits induced by parafascicular nucleus (PF) damage in young and aged rats, the authors gave rats a daily session of 2-way active avoidance until a fixed criterion was achieved. Four experimental groups were established in both young and aged rats: SS treatment after every conditioning session (SS groups), pretraining PF lesions (lesion groups), PF lesions and SS treatment (L + SS groups), and controls. SS treatment not only canceled the detrimental effects of PF lesions, but also improved conditioning in lesioned rats (L + SS groups). This effect was more powerful in aged rats. SS treatment compensated for memory deficits generated by hypofunctionality of arousal systems such as that involving the PF. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Taste aversion learning in young and adult rats.

Compared a total of 159 male Long-Evans rat pups and adults on their ability to learn taste aversions with 1- and 2-bottle tests, 2 different illness-inducing agents and flavors, and varying taste–illness delays. Rat pups learned taste aversions with either 1- or 2-bottle tests, but only with short taste–illness delays. Delays of 60 min were sufficient to block taste aversion learning in pups. Pups also failed to demonstrate neophobia to a novel taste. These findings suggest that pups forget taste information more rapidly than adults, perhaps because taste information is not so salient for pups as for adults. (29 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sensory preconditioning effects in young and adult rats.

Compared 64 90- and 64 25-day-old hooded rats on a test of sensory preconditioning (spc). Initially, 2 paired stimuli (s1, s2) were presented, following which s2 was paired with shock. The effects of s1 on 3 measures of lick-rate suppression were taken as indices of spc, these being: standard suppression ratio, lick latency following stimulus onset, and lick latency following stimulus offset. Results are as follows: (a) an spc effect was not demonstrated by the standard suppression ratio, and these data are explained by reference to possible habituation mechanisms or preexposure effects; (b) young ss but not adults showed an spc effect using onset latency; and (c) the reverse held true for the offset latency measure. These latter 2 findings are discussed in terms of differences in associative and discriminative capacities between young and adult ss. (french summary) (19 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Interhemispheric transfer of extinction of the active avoidance reaction in rats.

Employed cortical spreading depression (CSD) in 38 hooded Druckrey rats to study the lateralization of extinction of a jumping avoidance reaction. Under unilateral CSD, 181 nonreinforced trials were needed to extinguish the avoidance reaction acquired in 3 100-trial sessions of intact-brain training. During a 2nd extinction session, either with the same or with the contralateral hemisphere depressed, the mean number of trials to the extinction criterion (9 avoidance reactions in 10 consecutive trials) was 39 or 186, respectively. 5 extinction trials performed with the brain intact 1 hr before extinction with contralateral CSD decreased the number of trials to extinction to 98. Thus, extinction of active avoidance can be lateralized and interhemispherically transferred in the same way as acquisition of this habit. (22 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Transection of direct anterior thalamic afferents from the hippocampus: Effects on activity and active avoidance in rats.

Demonstrated the importance of the direct hippocampo-anterior thalamic component of the postcommissural fornix in the control of general locomotion and active avoidance; 40 adult male Sprague-Dawley rats were Ss in 3 experiments. Transection of anterior thalamic afferents from the hippocampal formation (subicular cortex), at the point where they exit from the fornix posterior to the septum, enhanced bidirectional active avoidance acquisition and increased general activity. This transection may also interrupt fibers to or from other thalamic nuclei and the anterior septum. However, destruction of connections of the anterior septum with the hippocampus, habenula, and thalamus by transection in the coronal plane anterior to the descending fornix columns, without damage to the subiculothalamic fibers, increased general activity levels without affecting active avoidance behavior. The activity increase in this case resembled that seen after septal lesions rather than that seen after hippocampal lesions. Thus, destruction of a single fornix component contributing afferents to the anterior thalamic nuclei reproduces at least part of the hippocampal syndrome. This suggests that these fibers contribute significantly to the control of these behaviors and may mediate active avoidance changes resulting from hippocampal and fornix damage. (40 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of daily administration of methamphetamine on multiple active/passive avoidance performance in rats

The effects of daily methamphetamine (M-Amp) treatment with (2 mg/kg/day, i.p.) were examined on multiple active/passive avoidance performance (MAP) in rats. After avoidance training, the animals were given M-Amp every day; on the days of learning sessions, which were on alternate days, the drug was administered at 15 min before the session. Daily administration of M-Amp produced enhancement of the number of respondings (running) as an excitatory dimension of behavior, disruption of immobilities as an inhibitory dimension, and impairment of successes as a discriminatory dimension, when compared with saline-treated rats. Following M-Amp withdrawal, recovery from these damages of learned behavior was observed, except the deterioration in the discriminative dimension. In conclusion, the MAP paradigm is good for assessing the behavioral effects of M-Amp treatment, making it easy to distinct the behavioral effects of M-Amp into excitatory-inhibitory and discriminative dimensions. It is important to distinguish the behavioral components induced by M-Amp, since the damage of learned avoidance performance consists of different dimensions in the M-Amp-treated rats. Impairment of discriminative behavior appears to demonstrate an attentional deficit, which may explain the behavioral disorderliness in M-Amp abusers who display no disturbance of apparent consciousness. These results are discussed with association of brain monoamine alterations.     

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)     

Preventing and alleviating hypothermia-induced amnesia in weanling and young adult rats.

Reminder (Experiment 1) and familiarization (Experiment 2) treatments were found to have similiar 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. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Deficient passive and one-way active avoidance acquisition following medial forebrain bundle lesions in rats.

In 3 experiments with 93 Long-Evans male hooded rats, cathodal electrolytic lesions of the medial forebrain bundle (MFB) at posterior hypothalamic levels produced a mild, transient hypodipsia and lowered jump thresholds to footshock. Lesions produced marked deficits in passive avoidance performance in a paradigm that paired discrete, linearly incrementing footshock intensities with contact of a water spout following 48 hrs of water deprivation. Injections of levo-dextro-5-hydroxytryptophan (75 mg g, ip), the immediate metabolic precursor of serotonin, had no effect on the passive avoidance performance of either experimental or operated control Ss. Lesions of the MFB also resulted in deficient acquisition in a 1-trial step-through passive avoidance paradigm not using motivation to drink and caused a severe acquisition deficit in a 1-way active avoidance task. Lesions of the septal nuclei produced lowered jump thresholds but did not affect acquisition in the 1st passive avoidance task. Results are interpreted as indicating a lesion-induced deficiency in fear learning, independent of the serotonergic functions of the MFB. (45 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Central catecholamine and peripheral noradrenaline depletion by 6-hydroxydopamine and active avoidance learning in rats.

Reports 3 experiments on the relationship between catecholamine (CA) depletion, plasma corticosterone (11-OHCS) levels, and active aversive learning in 108 male Wistar rats. A baseline study showed no significant relation between resting levels of 11-OHCS and central and/or peripheral CA depletion. On a 2-way avoidance learning task, depletion of brain CAs produced a widespread learning deficit. When both central and peripheral CAs were depleted, only escape learning emerged. Similar effects occurred on a 1-way task, but differences were not so marked. The findings are discussed in terms of a theory of CA-dependent cues. (33 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Localized behavioral effects of vasopressin on maintenance of an active avoidance response in rats.

Four experiments employing a total of 148 male Wistar rats investigated the role of lysine vasopressin (LVP) in maintaining shock-avoidance behavior under extinction conditions; a pole-jump situation was used. In 3 experiments, a single injection of 1 μg LVP was administered to Ss on the 1st acquisition session. The following results were obtained: (a) Resistance to extinction occurred when LVP effects were restricted to a single correct response; (b) similar effects occurred when the injection was delayed until immediately after the trial; and (c) classical conditioning alone was a sufficient behavioral substrate for these effects, but instrumental conditioning was more effective. In Exp IV, 1 μg LVP produced increased resistance to extinction when given in association with behavior which accelerated extinction. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Estrogen-induced changes in place and response learning in young adult female rats.

Many findings suggest that changes in circulating estrogen levels influence cognition, in some cases impairing performance and in others enhancing performance. One interpretation of these mixed effects is that estrogen biases the strategy used to solve a task. To test this idea, young adult female rats, ovariectomized for 21 days, were trained after acute hormone or control treatment in 2 very similar tasks with different cognitive requirements. One task required place learning and the other response learning. Rats given two 10-μg injections of estradiol 48 and 24 hr before training learned the place task significantly faster than did rats without estradiol. Conversely, rats without estradiol performed better on the response task than did rats with replacement. These data suggest that the cognitive actions of estrogen may be task-specific by modulating the relative contribution of different learning and memory systems. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of substantia nigra and caudate nucleus lesions on avoidance learning in rats.

Compared to 21 operated and 14 nonoperated controls, 36 male Sprague-Dawley albino rats with small bilateral lesions in the anteroventral caudate nucleus or the rostral substantia nigra were significantly impaired in the acquisition of 1-way active avoidance, passive avoidance requiring the inhibition of the previously acquired 1-way response, and shuttle-box avoidance. Ss with nigral lesions took significantly more trials to criterion than Ss with caudate lesions on 1-way avoidance. Results are considered in terms of the intimate anatomical and neurochemical relationships between these structures, and a circuit of structures involved in avoidance learning is suggested. (34 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sensory responsiveness and avoidance learning in rats.

Conducted an analysis of sensory responsiveness and avoidance learning in 3 experiments using 5 rat strains: MNR/Har/Lu, MR/Har/Lu, RCA/Lu, RHA/Lu, and RLA/Lu. Ss totaled 470. There were significant differences among the strains in response to electric footshock. Also, the strain-specific shock intensity as the UCS elicited significantly higher rates of avoidance learning as compared with the rates of avoidance learning under an equal but average level of shock intensity as the UCS. In general, discrete auditory and visual sensory modes as the CS produced almost the same rate of avoidance learning. The proportion of variation in avoidance learning attributable to strains was significant under all 6 experimental conditions except the no-discrete CS and strain-specific UCS conditions. (19 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The potassium concentration in cerebrospinal fluid in young and adult rats following complete brain ischemia. Effects of pretreatment with hypoxia

The potassium concentration in the cisternal cerebrospinal fluid (CSF) was measured following brain ischemia in rats of different ages which has been kept at normoxia or pretreated with hypoxia (PIO2 = 70 mmHg) for 24 h. In all age groups the potassium concentration rose following ischemia. The rate of rise was relatively slow in the 4-day rat and faster in 16- and 24-day rats; beyond this age the rate of rise became slower. Pretreatment with hypoxia significantly diminished the rate of rise in CSF potassium in 4- and 8-day rats, while no effect was observed in the older age groups. It is suggested that the rate of rise in CSF potassium is inversely correlated with the capacity of surviving a period of oxygen deprivation.     

Effects of scopolamine on activity and passive avoidance learning in rats of different ages.

A total of 320 albino CFE Sprague-Dawley rats aged 16-17, 20-21, 24-25, 28-29, and 70-85 days old were injected intraperitoneally with either scopolamine hydrobromide (SCOP-HBr) or scopolamine methylnitrate (SCOP-Me-NO-3) at 4 levels (0, .5, 1.9, or 2.0 mg/kg. The SCOP-HBr but not he SCOP-Me-NO-3 disrupted passive avoidance in Ss aged 20-28 days. A subsequent replication at higher doses (4.0, 8.0, and 16.0 mg/kg) with 56 70-84 day old adults and 64 16-day-old pups indicated that SCOP-HBr could disrupt passive avoidance in the adults but not in the pups. Results are consistent with the hypothesis that a cholinergic inhibitory system which mediates passive avoidance develops in the rat 16-20 days postnatally. (29 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)