Auditory sensitivity of the albino rat.

Determined the auditory sensitivity of the Sprague-Dawley albino rat by the conditioned suppression technique. The 3 Ss tested were found to have a range of hearing from 250 Hz to 80 kHz at 70 db (SPL). They were most sensitive to tones of 8 kHz but were almost as sensitive at 38 kHz. In contrast to previously published data, there was no evidence for a highly specialized tuning of the audiogram to tones in the 30–40 kHz region. In general, the audiogram of this strain of albino rat is quite typical of mammals of the same size and, furthermore, closely approximates the mammalian mean in most essential features. (35 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Disturbances of neophobia and taste-aversion learning after bilateral kainate microlesions in the rat pallidum.

These experiments aimed to elucidate feeding-associated behavioral roles of globus pallidus (GP) neurons in gustatory functions: The effects of bilateral microiontophoretic kainate (KA) lesions of the ventromedial pallidal (vmGP) region on neophobia and conditioned taste aversion (CTA) were studied. Lesioned rats displayed strong and persistent neophobia to a mild citric acid solution. Neuron-specific damage to the vmGP also prevented rats from proper acquisition of CTA. Rats that previously showed normal neophobia and successfully learned CTA demonstrated difficulties in CTA retention after GP lesions. KA-lesioned rats, in addition, exhibited deficits in orientation reactions but did not have aphagia, adipsia, or motor disturbances seen after larger pallidal lesions. These findings suggest that neurons of the GP are significant in acquisition, memory storage, and retrieval mechanisms of feeding-associated taste information. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Social deprivation and stimulus satiation in the albino rat.

Conducted 2 experiments, with a total of 288 male Sprague-Dawley albino rats, to explore the mechanisms whereby social deprivation leads to increased sociability in rats. Exp I housed Ss alone or in pairs with additional nonsocial stimulation, with additional response opportunities, or with no added social surrogates for 3 wks prior to testing for sociability. Social deprivation led to a strong increase in sociability, and this was not ameliorated by stimulus or response enrichment. Exp II exposed alone or pair-housed Ss to handling, human contact, or no stimulation and found that human exposure did serve a social surrogate function. This result suggests that sociability in rats represents to some degree a search for complex and unpredictable stimulation. (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Grooming behavior and competitive dominance in the albino rat.

Compared dominance in 28 male Wistar rats manifested in water competition under 2 levels of deprivation, with grooming activity in a nondeprived state. While competitive dominance was significantly related to motivational level, grooming emerged as a more stable indicator of social ascendance and did not require prior manipulation of a biological state. Implications of this observation for broader aspects of social motivation are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stimulus control of defensive reactions in the albino rat.

Conducted 4 experiments with a total of 132 male Wistar rats to examine the characteristics of stimuli that produce unconditioned defensive reactions. Results show that neither the sound nor the smell of a cat, or the sight of a dead cat, produced freezing, but that either a moving cat or dog, or the abrupt and rapid movement of an inanimate card, resulted in freezing and failure to approach the stimulus object. It is suggested that movement is a major factor in the initiation of defensive responses and that movement of a neutral stimulus may enhance the acquisition of defensive responses to that stimulus. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Persistence in the absence of primary motivation in the albino rat.

Trained 24 male Holtzman rats under either partial reinforcement (PRF) or continuous reinforcement (CRF). Ss were subsequently pre-fed their daily ration in the form of reward pellets and immediately run in the same task under a CRF schedule. Results reveal that PRF-trained Ss persisted in the satiated state relative to CRF controls. These results, termed the satiation effect, present difficulties to theories of persistence which address only extinction tests. An interpretation utilizing a modification of A. Amsel's (1962) frustration hypothesis is advanced. Implications of this proposal for a general theory of persistence and the methodological advantages of the satiation technique are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of ovariectomy on meal pattern in the albino rat.

In a study with 24 female albino Sherman rats, it was found that after ovariectomy most Ss increased food intake while continuing to eat discrete meals. Meal size increased in ovariectomized Ss, whereas meal frequency decreased. It is suggested that ovariectomy impairs the onset of satiety during a meal but not the ability to regulate total intake through modification of intermeal interval. (21 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of paleocerebellar lesions on DRL performance in the albino rat.

18 male albino rats with paleocerebellar lesions and 8 controls were trained to barpress for food on continuous reinforcement (CRF) and differential reinforcement of low response rates (DRL) schedules. Ss with lesions showed normal acquisition of the CRF schedule, but they exhibited a marked deficit on the DRL task. This deficit was related to overresponding that appeared to result from an inability to inhibit the response, rather than from a dysfunction in timing ability or motor capacity. The DRL deficit, however, was overcome by the introduction of a salient stimulus object (wood block) into the operant situation. Although no explicit reinforcement contingencies were placed on interaction with the stimulus object, it appeared that the wood block facilitated the development of "collateral" behaviors that served to mediate the DRL interval. Results are consistent with the suggestion that the cerebellum may contribute to the sequential organization of complex behaviors. (51 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Some behavioral effects of entorhinal cortex lesions in the albino rat.

Performed 7 experiments on groups of adult male albino Sprague-Dawley rats (N = 74). Ss with lesions in the entorhinal cortex (a) were hyperactive in a novel open field and in activity wheels, (b) were less responsive to punishment than controls, and (c) showed complex changes in several avoidance behaviors. Mild hyperphagia was observed only when the lesions extended into the subiculum. Results support the idea that the entorhinal cortex may relay information from the cingulate cortex and olfactory areas to the hippocampus. It is suggested that entorhinal-midbrain connections demonstrated in other species may serve important functions in the rat. (36 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Self-stimulation of preoptic and lateral hypothalamus during behavioral thermoregulation in the albino rat.

Explored self-stimulating behavior in 5 male albino rats under ambient temperatures of 2, 12, 25, and 35.C while radiant-heat reinforcement was concurrently available. Preoptic self-stimulation was accompanied by hypothermia even at neutral temperatures, and in the cold, preoptic self-stimulation behavior was maintained alternating with the use of the heat-lamp lever. Conversely, self-stimulation of the lateral hypothalamus produced hyperthermia at neutral temperatures. In the cold, lateral hypothalamic self-stimulation was suppressed, although maintained sufficiently to preserve normal body temperatures without use of the heat lamp. High-temperature stress suppressed both preoptic and lateral hypothalamic self-stimulation. The interpretation suggests that electrical stimulation of the preoptic area signals a pseudowarmth state which results in activation of heat-loss mechanisms. (15 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cholesterol esterification activities in the intestines and pancreas of the albino rat

Cholesterol esterification activities in intestines and pancreas are much greater with unsaturated fatty acids than with the saturated ones; the maximum activity is with arachidonic acid in intestines and with oleic acid in pancreas. The pancreatic cholesterol esterification activity is higher than the intestinal one.     

Effects of differential rearing on cortical evoked potentials of the albino rat.

3 groups of Sprague-Dawley albino rats were reared in different environments from weaning to the age of 95 days. One group was in a visually enriched environment (n = 8), a 2nd group was in an auditorily enriched environment (n = 8) and a 3rd group, controls, received no enrichment (n = 16). Photic and auditory evoked potentials were recorded in unanesthetized Ss from chronically implanted epidural electrodes over the visual and auditory cortex. Ss whose enrichment included visual stimulation yielded significantly shorter latencies in their photic evoked responses recorded over the visual cortex than latencies recorded from controls or from Ss whose enrichment excluded visual stimulation. (17 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cones survive rods in the light-damaged eye of the albino rat

Exposure to constant light causes extensive rod photoreceptor damage but spares the photopic system in albino rats. The rod branch of the dark-adaptation curve shows considerable elevation in threshold; the cone branch is hardly affected. Longer exposure and chromatic adaptation suggest that there are three cone mechanisms with peaks near wavelengths of 450,520, and 560 nanometers.     

Repeated trials with the albino rat in the open field as a function of age and deprivation.

Each of 3 experiments demonstrated that female Sprague-Dawley albino juvenile rats (n = 24) become increasingly active during 10 consecutive trials in the open field; adults (n = 24) did not show this day-to-day change. Age-related activity change was unaffected by food deprivation and is interpreted to be a consequence of the greater curiosity and ease in familiarization with a novel environment among juveniles. The greater intensity of ambulation among immature Ss may provide an explanation for age-related differences in appetitive learning. (24 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Spontaneous choroid plexus carcinoma in an albino rat

The development of autosomal dominant DOPA-responsive dystonia (AD-DRD) is stipulated by mutation in GTP-cyclohydrolase I gene. GTP-cyclohydrolase I is the first and key enzyme of tetrahydrobiopterin biosynthesis. Its deficiency in nigrostriatal dopaminergic neurons cause a decrease in tyrosine hydroxylase activity and therefore dopamine deficiency. However, administration of low doses of dopamine can control the development of AD-DRD. Determination of GTP-cyclohydrolase I activity in mononuclear blood cells is convenient diagnostic method.     

Conditioned taste aversions and neophobia in rats with hippocampal lesions.

In Exp I extensive hippocampal lesions retarded, but did not prohibit, the conditioning of a strong taste aversion to physiological saline (the CS) in 16 male Holtzman albino rats when illness (the UCS) was induced by apomorphine injection 15 min following ingestion of the saline. In Exp II hippocampal lesions reduced the aversiveness of novelty in a drinking fluid for 21 thirsty Ss. It is suggested that the mild impairment of taste aversion learning in Ss with hippocampal lesions was not the result of destruction of mnemonic mechanisms that serve to span the long CS-UCS interval but rather that the reduced intensity of the aversion resulted from a lesion-altered neophobic disposition that weakened the saliency of the novel flavor CS. (51 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

ACTH and ACTH4–20 modification of neophobia and taste aversion responses in the rat.

A series of 6 experiments assessed the effects of ACTH and the ACTH analog ACTH4–20 on drinking in conditioned taste aversion and neophobic situations using a total of 168 male Sprague-Dawley rats as Ss. Both substances delayed the extinction of a conditioned taste aversion established by a single pairing of lithium chloride with milk (Exp I). However, in this situation, the ACTH parent peptide was more potent behaviorally. ACTH supressed milk consumption in Ss with no toxicosis experience (Exp II). This effect was apparently not due to the conditioning of a taste aversion (Exp III) with ACTH serving as a weak aversive UCS. Exogenous ACTH (Exp IV) or ACTH4–20 (Exp V) did not enhance neophobia; however, repeated injections of ACTH suppressed drinking. This ACTH suppression was related to the familiarity/novelty of the substance being consumed. The neophobic response to milk was not accompanied by pituitary-adrenal activation (Exp VI). Both neophobic and conditioned taste aversion situations appear to be useful for assessing peptide effects on consummatory behavior. (36 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of auditory cortical lesions on pure-tone sound localization by the albino rat.

Used 2-choice and 3-choice tests to evaluate the effects of bilateral auditory cortical lesions on pure-tone sound localization by 10 male albino rats. Both tests required that Ss approach a distant sound source to obtain water reinforcement. Stimuli were single noise and tone bursts, 65 msec in duration including 20-msec rise and fall times. Tone frequencies were 2, 4, 8, 16, and 32 kHz adjusted to 40 dB (sound pressure level) above the S's absolute threshold. Five Ss were tested in the 2-choice situation following bilateral ablation of auditory cortex. Some reduction in performance was observed relative to normals, but impairments were not severe. Similar results were obtained for 2 brain-damaged Ss tested in the 3-choice situation. Thus, the ability to localize sounds in space remained intact after complete destruction of auditory cortex, and there was no indication of a frequency-dependent deficit. Findings are considered in relation to the more severe deficits observed in other mammals after lesions of the auditory cortex. (30 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)