The hooded allele and selection of wild Norway rats Rattus norvegicus for behavior

Selection of wild gray rats for domestication (tame behavior) resulted in a sharp increase in the frequency of heterozygotes at the h allele of hooded, the main locus of rat depigmentation. The observed effect of the selection on the manifestation of the h allele is compared with similar effects giving rise to piebaldness in other animals subjected to experimental domestication. The results are discussed in terms of genetic specificity of piebaldness and of the selection vector.     

Recovery of function after neonatal ablation of the auditory cortex in rats (Rattus norvegicus)

A number of traditional Chinese medicinal herbs have become extremely interesting in the search for potential BRMs in the international medical community, especially in the United States and Japan. Naturin, a new Chinese medical herb produced by XingYa Pharmaceutical Co., Ltd., has enhanced immune response, inhibited tumor metastases and retroviral infection in animal models as well as in clinical studies. The results demonstrated that the inhibition of Natural Killer (NK) and Lymphokine-activated Killer (LAK) cell activity and lymphocyte proliferation was compromised by tumor metastases and retrovirus infection (Murine AIDS), even immunosuppression induced by surgical amputation can be restored by Naturin. It is also shown that Naturin can protect the mice from lethal total body irradiation. These studies indicated that Naturin possesses immunomodulatory effects in vivo for a broad range of stresses. The results of the clinical studies on Naturin have demonstrated: (a) significantly improved symptoms of patients, including MDS, acute and chronic leukemia, aplastic anemia, lung cancer, and association with the increased number and percentage of CD4 (Helper T-cell) which have been reduced in some patients, (b) Lymphocyte proliferation and NK cell activity which were suppressed in cancer patients can be significantly restored by Naturin treatment, (c) the addition of Naturin treatment to patients receiving radiotherapy and chemotherapy augments immune response and reduces radiation and chemotherapy injury, and (d) no cytotoxic side effects were found in patients given Naturin treatment for up to eight months.     

Photic responses of suprachiasmatic area neurons in diurnal degus (Octodon degus) and nocturnal rats (Rattus norvegicus)

Photic sensitivity of cells in the suprachiasmatic nuclei (SCN), the principal pacemaker of the mammalian circadian system, has been documented in several species. In nocturnal rodents, the majority of photically responsive SCN cells are activated by retinal illumination. One report identified mostly photic suppressions among SCN cells in a diurnal rodent, studied under somewhat different conditions. We examined photic sensitivity of SCN cells in a predominantly diurnal rodent, the degu, studied in vivo under identical conditions to rats, and found that a large majority of photic SCN cells were suppressed by light. In both rats and degus, SCN cells were more responsive to light during the subjective night than during the subjective day. Light-responsive cells did not show a daily rhythm in baseline firing rates in either species, but rat SCN cells that did not respond to light were more active spontaneously during the subjective day. Light-unresponsive SCN cells in degus did not show a similar pattern. There are substantial differences in the neurophysiological activity and photic responsiveness of SCN cells in diurnal degus and nocturnal rats.     

Appetitive motivational states differ in their ability to augment aversive fear conditioning in rats (Rattus norvegicus)

An expression map containing 48 ESTs was constructed to identify a tumor-suppressor gene involved in B-cell chronic lymphocytic leukemia (B-CLL), which was previously assigned to chromosome band 13q14.3 close to genetic markers D13S25 and D13S319. Thirty-nine of these 48 ESTs, together with 11 additional ones listed in databases, were initially assigned to chromosome 13q14 between markers D13S168 and D13S176. Nine others have recently been located in the D13S319 region. Our results indicate that 48 of the 59 ESTs analyzed belong to a YAC contig of chromosome 13 band q14, and 22 are contained on YAC 933e9, which encompasses the B-CLL critical region. Ten of these 22 ESTs were accurately assigned on a PAC, BAC, and cosmid contig encompassing the smallest minimal deletion area described so far in B-CLL, and 20 were tested for their expression on 27 normal or tumor tissues. One EST appears to be a likely candidate for the tumor-suppressor gene involved in B-CLL.     

Isolation of cDNA encoding full-length rat (Rattus norvegicus) poly (ADP-ribose) polymerase

Poly(ADP-ribose) polymerase (EC 2.4.2.30) is a nuclear enzyme which binds to DNA breaks and then catalyzes the covalent modification of acceptor proteins with poly(ADP-ribose). Poly(ADP-ribose) polymerase activity contributes to the recovery of proliferating cells from DNA damage and to the maintenance of genomic stability, which may be mediated by effects on chromatin structure, DNA base-excision repair and cell cycle regulation. We established the complete cDNA sequence of rat poly(ADP-ribose) polymerase by RT-PCR and direct sequencing of amplification products and compared it with that of other mammalian species. The amino acid sequence homology is strikingly high. The best conserved regions are the known functional modules of poly(ADP-ribose) polymerase.     

Isolation and properties of myoglobins from rat (Rattus norvegicus) skeletal muscles

A simple test of critical thermal maximum (CTM) to assess a break-down of heat-escape behavior in rats is described. Experiments were performed on 18 unrestrained adult Wistar rats of both sexes. Hypothalamic and intraperitoneal (i.p.) temperatures as well as motor activity were simultaneously and continuously recorded in the rats exposed to heat. When animals were growing restless, as evidenced by an increase in their motor activity, which was usually recorded at hypothalamic temperatures well above 41 degrees C, we started testing CTM. To assess heat-escape behavior we used a precooled cooling bar (a part of a camp-cooler) which was placed at intervals in a climatic chamber. The hyperthermic rats, given the bar for 30 s, mounted it vigorously until they failed at particular levels of brain and body temperatures which were recognized as respective CTM values. Rapid external cooling of rats prevented lethal effects of the heat exposure. We were able to show effects of timing of heat exposure on heat tolerance. We also managed to detect small but significant differences in heat tolerance of warm-reared (an increase), cold-reared (a decrease), and bacterial-endotoxin-treated (an increase) rats. The heat-escape behavior was less heat-resistant than selective brain cooling response which was still present at CTM point. In conclusion, our CTM test is a safe and reliable way to study heat tolerance in rats.     

Maternal age and male behavior in relation to successful reproduction by female rats ( Rattus norvegicus ).

Results of 3 experiments with 120 rats show that multiple ejaculatory series may be critically important for successful reproduction by multiparous old females near the end of their active reproductive lives. Multiple series were essential for successful pregnancy, apparently because more than one series was necessary to induce functional luteal activity. Thus, (a) females receiving just one series failed to show the cessation of regular estrous cycles which characteristically follows induction of a functional luteal phase; (b) direct measurement of plasma progestins by radioimmunoassay revealed that only those females receiving more than one series had circulating levels significantly higher than unmated, normally cycling controls; and (c) administration of exogenous progesterone increased significantly the incidence of successful pregnancy among females allowed to mate through only one series. In addition to facilitating the occurrence of pregnancy, multiple series also increased both the number of eggs released at ovulation and the number of embryos present and developing 12 days later. It is concluded that multiple series may function as a behavioral mechanism for prolonging the female's active reproductive life. (31 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A comparison of temporal decay in place memory tasks in rats (Rattus norvegicus) with lesions affecting thalamus, frontal cortex, or the hippocampal system

Three experiments compared the effects of lesioning areas of thalamus, cortex, and the hippocampal system on delayed matching (DMTS) and nonmatching (DNMTS) to sample. Temporal decay was measured by comparing performances at different retention intervals (RIs) for rats trained to stability. Lesions of the lateral-internal medullary lamina site in thalamus and the medial wall area in frontal cortex produced impairments that were significantly greater than for lesions of the mediodorsal nucleus in thalamus, the fornix, or the dorsal hippocampus. The effects of lesions on temporal decay differed depending on how RIs were manipulated. When RIs were manipulated within training sessions, the DMTS and DNMTS impairments were delay independent (i.e., none of the lesions increased the rate of temporal decay). When RIs were manipulated between sessions, thalamic lesions were associated with an increase in the rate of temporal decay of DNMTS.     

Preference for novel flavors in adult Norway Rats ( Rattus norvegicus).

The authors fed rats 1 of 2 distinctively flavored, roughly equipalatable diets for 3 days then offered them an ad libitum choice between the 2 diets. For 3 days, subjects exhibited a reduced relative intake of whichever diet they had previously eaten (Experiment 1). Such reduction in relative intake was as effective as a toxicosis-induced conditioned aversion in determining subjects' food choices (Experiment 2). The strength of exposure-induced reduction in relative intake did not depend on similarity of the 2 diets offered for choice either to each other or to subjects' maintenance diet (Experiment 3) but did require continuous exposure to a diet (Experiment 4). These experiments provide the first evidence of a robust, exposure-induced decrease in food preference in rats lasting for days rather than minutes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Unconditioned sexual incentive motivation in the male Norway Rat (Rattus norvegicus).

Sexual incentive motivation was evaluated in a procedure consisting of a large open field where incentive animals were confined behind wire mesh openings. When sexually inexperienced male rats (Rattus norvegicus) were exposed to the receptive female-male incentives, they spent more time close to the female. If the incentives were receptive female-nonreceptive female, the receptive female was preferred. However, when the alternatives were nonreceptive female-male, no preference was obtained. Castration abolished preference for the receptive female, and treatment with testosterone propionate restored it. Estradiol plus oil is as efficient as estradiol plus progesterone for giving the ovariectomized female incentive properties. The living female can be replaced with female odor. Sexual experience did not have any long-term effects on the female's incentive value, but immediately preceding limited sexual activity enhanced it. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Auditory Categorization of Complex Sounds by Rats (Rattus norvegicus).

Little research has explored the auditory categorization abilities of mammals. To better understand these processes, the authors tested the abilities of rats (Rattus norvegicus) to categorize multidimensional acoustic stimuli by using a classic category-learning task developed by R. N. Shepard, C. I. Hovland, and H. M. Jenkins (1961). Rats proved to be able to categorize 8 complex sounds on the basis of either the direction or rate of frequency modulation but not on the basis of the range of frequency modulation. Rats' categorization abilities were limited but improved slowly and incrementally, suggesting that learning was not facilitated by selective attention to acoustic dimensions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Evolution of grass-cutter (Thryonomys swinderianus) inflammation markers: comparison with rabbit (Oryctolagus cuniculus) and rat (Rattus norvegicus)

An inflammatory reaction was induced in grass-cutters (Thryonomys swinderianus) by injecting turpentine. The changes in the plasma haptoglobin, fibrinogen, alpha 2 macroglobulin and immunoglobulin G was followed for 23 days by immunonephelometry. The results were compared to rat and rabbit. They showed that (a) the inflammatory reaction is delayed in the grass-cutter compared to rats and rabbits; (b) the concentration of haptoglobin increases less than in rat and rabbit; (c) the fibrinogen concentration is very low in the grass-cutter, despite hypercoagulability of blood; (d) the changes in the plasma alpha 2-macroglobulin in the grass-cutter seems to be comparable to that of rabbit alpha 1 macroglobulin in amplitude and in its slow return to the initial concentration; and (e) fibrinogen and haptoglobin are suitable markers for grass-cutter inflammation monitoring.     

Fetal and postnatal development of palmar, plantar, and digital pads, and flexion creases of the rat (Rattus norvegicus)

Fetal development of the hands and feet of rats was investigated to determine the feasibility of using rats as an experimental model for studying the factors influencing early development of the hands and feet, and especially the dermatoglyphics in humans. Eighty rats fetuses of 14-21 days gestational age and 80 newborn rats of 0-7 days of age were used to study the morphological features of the palmar, plantar, and digital areas and to determine the timing of appearance and the location of the volar pads and flexion creases. Comparisons between analoguous developmental stages of rat and human fetuses demonstrate striking similarities in overall fetal development. Marked differences, however, were found between rat and human fetuses in the timing of developmental milestones and in some morphological features. The results indicate that rats can serve as a useful experimental model in studies of the utility of the epidermal ridge configurations and flexion creases in medical disorders, provided that the differences in the timing of development are taken into consideration.     

Bi-phasic allometric growth of the small intestine, cecum and the proximal, middle, and distal colon of rats (Rattus norvegicus Berkenhout, 1764) before and after weaning

We studied whether the growth of the intestinal tract changes at weaning. We weighted fresh tissue and measured segment length of the small intestine, cecum and proximal, middle, and distal colon of 45 male and 51 female F344/Yit rats (Rattus norvegicus Berkenhout, 1764) of 0 to 428 days old. We performed correlation analysis among tissue weight, segment length and empty body weight after logarithmic transformation of the data. The growth of the small and large intestine was biphasic. Intestinal growth exceeded body growth during the suckling period and slowed down suddenly after weaning. Sexual differences existed in intestinal growth, although much smaller than the difference before and after weaning. These results appear to suggest that the size of intestinal tract of the rat does not adapt to nutritional changes at weaning, but prepare for weaning beforehand.     

The effects of audiogenic stress on the growth of long bones in the laboratory rat (Rattus norvegicus)

It has been demonstrated that experimentally induced cold stress produces a stunting effect in the limbs of rodents. Such an effect has also been reported for the dentition and limbs in response to other stressors (heat, cold). Recent research into the effects of various stressors on the magnitude of fluctuating dental asymmetry demonstrated that general stress increases the magnitude of fluctuating dental asymmetry in experimental animals. However, no increase in the magnitude of fluctuating asymmetry of limb length was reported as a response of general stress. In the light of such studies the present research investigates the relationship between stress and the mass per unit length of limbs. The stressor chosen for the present study was audiogenic stress as it has been demonstrated to induce the general stress syndrome and also increase the magnitude of fluctuating dental asymmetry. Audiogenic stress is found to produce increases in the magnitude of fluctuating asymmetry of the mass per unit length of long bones in the laboratory rat. Also the absolute values of long bone length and mass per unit length are significantly smaller in stressed animals when compared with controls. The relationship between the stress induced stunting of linear dimensions and the increase in the magnitude of fluctuating asymmetry is discussed.     

Positive Geotaxis in Infant Rats (Rattus norvegicus) : A Natural Behavior and a Historical Correction.

Infant rats (Rattus norvegicus) placed on a shallow incline (2°, 4°, or 8°) oriented and moved downhill within 1 min; that is, they displayed positive geotaxis. Their downhill translocation increased with angle of inclination. A variety of possible behavioral elements (e.g., initial orientation, rotational movements, ambulatory velocities) were eliminated as explanations of the geotaxis. Wall contact was recognized as a determinative event: Pups on the inclines showed no orientation with respect to the geogravitational stimulus before contacting a wall. The event of wall contact, however, evoked reliable downhill orientation and more linear movements. Positive geotaxis was created by pups' orientation against walls and an associated increase in movement velocity. This is a distinct perspective on a behavioral response that replaces a traditionally misinterpreted phenomenon. The authors discuss the ecological validity and historical context of these findings. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Symptom-dependent taste aversion induced by an anticoagulant rodenticide in the brown rat (–Rattus norvegicus–R).

In a series of 3 experiments with different experimental paradigms, feeding patterns of laboratory rats (Rattus norvegicus) were monitored in 2-choice feeding tests after intubation with a sublethal dose of an anticoagulant rodenticide. The authors report for the first time that contrary to accepted wisdom, anticoagulants can induce taste aversions. Furthermore, we report behavioral symptoms within the 1st day after dosing. Our data suggest that the taste aversion is induced through an inhibition of the vitamin K cycle and is transient, attenuating over the same period as the levels of vitamin K-dependent proteins return to normal. Because the taste aversion is expressed most strongly when symptoms are most pronounced and is not expressed after symptoms have disappeared, the authors term this novel form of control symptom-dependent taste aversion. (PsycINFO Database Record (c) 2010 APA, all rights reserved)