Male Rats Of Sprague-Dawley Strain Research Articles

Lack of evidence for an impairment of tuberoinfundibolar dopaminergic neurons in aged male rats of the Sprague-Dawley strain.

Circulating prolactin (PRL) levels, dopamine (DA) content, in vitro basal and stimulus-evoked endogenous DA release from arcuate-periventricular nuclei median-eminence fragments were studied in young (4 months) and old (24-25 months) male rats of Sprague-Dawley strain. Serum PRL levels did not differ in young and aged animals. In addition DA tissue content, basal and K+- or d-amphetamine evoked endogenous DA release did not show age-related differences. These results suggest that in male rats of the Sprague-Dawley strain the activity of tuberoinfundibular dopaminergic (TIDA) neurons does not change during senescence, unlike what happens in other strains of rats.

Negative report on trichloroethylene-induced pneumatosis cystoides intestinalis in rats

In recent years it has been suggested in Japan that occupational trichloroethylene exposure will induce primary pneumatosis cystoides intestinalis coli. A series of two experiments were conducted to ascertain the cause-effect relationship between trichloroethylene and pneumatosis as follows: In the first experiment, 12 male rats of Fischer strain were exposed to trichloroethylene at a nearly lethal concentration for 12 wk. Five out of 12 rats died during the experiment, and body weight gain was extremely depressed. However, neither pneumatosis nor histological changes were observed. No changes were observed in 4 control rats as well. In the second experiment, 38 male rats of Sprague-Dawley strain were exposed to 800, 200 or 50 ppm trichloroethylene over a period of 12 wk. Two out of 13 rats of the 800 ppm group died, and body weight gain was suppressed. Mild suppression in body weight gain was also observed in the 200 ppm group. However, pneumatosis was not observed in any rats of trichloroethylene groups. No pathological changes were observed in 13 rats of the control group. The foregoing results suggest that trichloroethylene cannot induce pneumatosis cystoides intestinalis in rats of these two strains. Inasmuch as rats are not prone to develop pneumatosis, the possibility for trichloroethylene to induce this disease in man cannot be denied.

Antagonism of the behavioral effects of L-phenylisopropyladenosine (L-PIA) by caffeine and its metabolites

Three male Sprague-Dawley strain rats were trained to respond under a multi-component time out 5 min variable ratio 15 (VR15) schedule of food reinforcement. Cumulative, within session dose-effect curves were determined for L-PIA alone and after methylxanthine pretreatment. L-PIA alone produced dose related decreases on VR15 responding at doses between 0.032 and 0.178 mg/kg. Significant antagonism of L-PIA was demonstrated from pretreatment with caffeine, theophylline, theobromine, paraxanthine, 3-methylxanthine, and 7-methylxanthine. No antagonism of L-PIA was observed following pretreatment with 1-methylxanthine. Consistent with the adenosine receptor blockade hypothesis, caffeine also antagonized the effects of 5'-N-ethylcarboxamide adenosine (NECA) on VR15 responding.

Cross-sectional Properties of the Rat Femur as Influenced by Forced Running Exercise

Flattening of limb bones is not infrequent in prehistoric population as well as in modern hunter-gatherers. Platycnemia is well-documented in materials from Japanese prehistoric 'Jomon' period. Interpretation for the reason of this bony feature, however, is still controversial with respect to the mechanical stress due to a hard physical exercise or nutritional elements. This study aims at identifying the factors mainly responsible for the flattening by using experimental animals.Effects of exercise and diet programs on the cross-sectional properties of the femur were studied in 40 male rats of Sprague-Dawley strain. They were divided into 6 experimental groups, (I) Ordinary Feeding a Non-Exercise Group, (II) Ordinary Feeding a Exercise Group, (III) Restricted Feeding a Non-Exercise Group, (IV) Restricted Feeding a Exercise Group, (V) Free Feeding a Non-Exercise Group, (VI) Ordinary Feeding a Hard Exercise Group (8 rats for groups I-IV and 4 rats for groups V and VI). Each group was raised from 21 days through 110 days age. Restricted feeding groups (III and IV) were fed 60% weight of diet which was ate by ordinary feeding groups (I or II) on the previous day. Free feeding group was fed freely all day long. From 30 days age, the exercise groups were trained to run 20 minutes in a day at a maximum speed of about 40m/min on a newly devised treadmill ('Labotrainer', Clea Japan Inc.) which seemed to elicit least exercise stress in animals. Hard exercise group was trained twice in a day according to the same program. Feeding, running, and light and darkness cycle schedule was arranged so as to minimize the individual difference in food intake and spontaneous activities. It has been reported elsewhere (MATSUMURA, 1982) that the body dimensional development in general suggested an undisturbed physical growth in the present animals. After the training period, the right femur was removed and femoral cross sectional properties as taken at the middle of the femur shaft were examined. While forced running exercise had no significant effect upon the magnitude of the cross sectional area of the femur, it had an unequivocal effect upon the other cross sectional properties; the femur of exercise groups had a smaller cross sectional index, or was significantly flattened, with its major principal axis oriented more antero-posteriorly. This trend was less pronounced in limited-diet groups. Restriction of food intake scarcely had effects upon cross sectional index nor upon major principal axis of the femur, although it exerted a marked negative influence on the cross sectional area.

Effect of pimozide on neural systems driven by brain rewarding stimulation: A [14C] 2-deoxyglucose analysis.

Present study was to examine the effect of pimozide on neural systems driven by brain rewarding stimulation of medial fore-brain bundle (MFB) by means of [14C] 2-deoxyglucose (2-DG) autoradiography. The subjects were male rats of Sprague-Dawley strain. They were implanted with a monopolar electrode in or near MFB at hypothalamus. The rats were set to self-stimulating in Skinner box, each lever press yielding a train of 66 cathodal pulses, 0.1 msec wide, at 100 Hz (200-400 μA). The rats self-stimulated by pressing a lever in a box during 45 min period following the i.p. injection of 30 pCi of [14C] 2-DG. Rat brains were sectioned on cryostat. The autoradiographic images were analyzed by Image Computer. Pimozide produced an extinction-like decline in the performance of rats rewarded with brain stimulation. Analysis by means of [14C] 2-DG autoradiography of neural systems driven by brain stimulation revealed effects in diagonal band of Broca, in MFB, and/or fornix and in anterior ventral tegmentum. Same systems were still activated by automatic stimulation in rats treated with pimozide. The clear effect of pimozide showed greatly elevated activity in lateral habenula. The results suggest that pimozide’s effect is mediated by the interconnecting lateral habenula with diagonal band of Broca and/or anterior ventral tegmentum.

Studies on the difference of salivary response to catecholamines in developing rat submandibular gland

The response of submandibular salivary secretion in rats of several age groups was examined with the administrations of α and β-adrenergic agonists.Submandibular saliva was collected intraorally from male Sprague-Dawley strain rats of 2 to 8 weeks of age as immature, and 12-15 weeks of age as mature. Noradrenaline (2mg/kg) or phenylephrine (6mg/kg) as α-adrenergic agonists, and isoproterenol (30mg/kg) as β-adrenergic agonist were administered i. p. for collecting saliva.Results obtained were as follows: The response of salivary secretion, such as salivary volumes, flow rate and protein concentration, in the rats of 7-8 weeks did not significantry differ from that of mature rats. In the response to β-adrenergic agonist by disc electrophoresis, types of secreted proteins in 6-week rats resembled that in mature rats. In the response to a-adrenergic agonists by disc electrophoresis, types of secreted proteins in 7-week rats resembled that in mature rats. However, types of secreted proteins in the rats of 2 to 5 weeks of age were similar to the case of β-adrenergic agonist. The result of analysis of isoelectric focusing indicated that secreted proteins by α-adrenergic agonist in 7-week rats resembled those in mature rats. By chronic noradrenaline (1mg/kg) administration, the growth rates of body weights and submandibular wet weights in 4-week rats were slightly suppressed as compared with those in the control rats.

Pathological observations on natural cases of sialodacryoadenitis of rats.

Pathological observations were carried out on 100 male rats of Sprague-Dawley strain obtained from 5 outbreaks of sialodacryoadenitis (SDA). In accordance with clinical and macroscopic findings, principal microscopic changes were found in the salivary (submaxillary and parotid) and Harderian glands. Lesions observed in these different glands were essentially similar to each other, and characterized by degenerative changes in the epithelial cells of the ducts and acini associated with marked and extensive serous inflammation in the interstice. Furthermore, squamous metaplasia of the ductal epithelia was a common feature to these glands in the late stage of the disease. Some differences, however, were detected between the changes of the salivary glands and those of the Harderian glands. Firstly, the ductal epithelial cells were affected at first and the acinous epithelial cells were damaged only secondarily in the active inflammatory process in the salivary glands, while both ductal and acinous epithelial cells were involved equally in the primary lesion in the Harderian glands. Secondly, the increase in connective tissue elements in the reparatory process was extremely marked in the Harderian glands as compared with the salivary glands. Consequently, in the lesion of Harderian glands in the late stage, original construction was almost indiscernible, and the ducts and acini were only recognized as disseminated islets in actively proliferated connective tissue elements.

Lung Retention of Metallic Fumes

From the results of theoretical and experimental studies on the aerosol retention in lung, it has been assumed that the effect of particle size on the lung retention rate of aerosol would uniformly depend upon the aerodynamic mass median diameter (AMD or Da).In order to elucidate this assumption, the author made an inhalation experiment using lead (Pb) and tellurium (Te) fumes which had monodispersed spheric but different specific gravities for rats. In the experiment several particle sizes of Pb or Te fume generated by the high frequency electric furnace type fume generator were inhaled by SPF male rats of Sprague-Dawley strain in a head-only exposure chamber for 90min. After inhalation, the lung was taken out instantly from the rat's body, and the weights of metallic fumes retained in each rat lung were measured by atomic absorption analysis. The relative lung retention rates (RL) of metallic fumes in rats were calculated considering the exprimental conditions such as the fume concentration in the exposure chamber, the exposure period and respirating minute volume of rat. However, minute volume of each rat could not be measured easily, so that it was used uniformly 100ml/min for minute volume of rats because body weight of each rat showed little difference among each other.As results of the experiment, the following relationship was found to exist between RL and Da in both the cases of inhalation of Pb and Te fumes: RL=K⋅Da-n. The author named the index number of lung retention as n in this equation. According to the above assumption, n value should be constant regardless of the kind of aerosol material. However, n were 0.72 of Pb fume and 0.36 of Te fume in the present experiment. This difference might be produced by the physico-chemical properties and biological activity of metallic fumes.

STUDIES OF THE EFFECT OF IRRADIATION OF CELLULAR PARTICULATES. VI. COMPARISON OF UNCOUPLING AT THE THREE PHOSPHORYLATING SITES

White male rats of Sprague-Dawley strain were exposed to 1000 r total-body γ-irradiation. Measurements of the uncoupling at each of the three phosphorylating sites in mitochondria isolated from liver and spleen were made. The results indicate that the terminal step (oxidation of reduced cytochrome-c) is the most sensitive of the three and that the great majority, if not all, of the observed uncoupling may result from damage to this step.