Delayed postnatal behavioral development in spontaneously epileptic rats and tremor rats, and poor operant performance in spontaneously epileptic rats

Postnatal behavioral development and learning ability of operant performance were examined in spontaneously epileptic rats (SER: zi/zi, tm/tm), and the original tremorous mutant strains of rats, tremor rats (tm/tm) and zitter rats (zi/zi) and their controls. Before the eyes opened, the increase in body weight and the age of achieving the righting reflex on a surface were no significantly different between the SER and their littermates without epileptic seizures (SER-N: zi/zi, tm/+ or zi/zi, +/+), and between tremor rats and the original strain Kyo: Wistar rats. After the eyes opened, the increase in body weight, age of achieving the righting reflex in air and traction performance, and the development of rotarod performance, were delayed in SER and tremor rats in comparison with other groups of rats. The zitter rats were apparently inferior in their development of rotarod performance in comparison with the same zitter homozygous SER-N. Operant performance was more inferior in SER than in SER-N and in tremor rats than in Kyo: Wistar rats. The differences were much more marked between SER and SER-N than between tremor and Kyo: Wistar rats. Thus, homologous tm genes and the coexistence of homologous tm and zi genes have an inhibitory effect on postnatal behavioral development and learning ability.     

Regurgitation and choke in rats

Male and female F344 rats choked on fecal pellets and regurgitant during the course of two long-term experiments. Each study involved feeding standard and high bulk diets containing 10% wood cellulose or 10% chrysotile asbestos fiber. Choke deaths occurred at all stages of the experiments. A total of 36 of 774 (4.6%) rats in the two studies died of choke. Females died of choke more frequently (26/382 or 6.8%) than did males (10/392 or 2.6%). Rats on high bulk diets were affected more frequently (33/571 or 5.8%), especially those on 10% asbestos diet (26/311 or 8.4%, than rats consuming standard diet (3/190 or 1.6%). The reason for the difference between females and males was not determined. Although choke may be related to some characteristics of high nonnutritive bulk feed fed in pellet form, the higher risk for females even on standard diet (3/95 or 3.2%) than for males (0/95) indicated that more than one factor operated in the etiology of these events.     

Neuroprotective properties of aucubin in diabetic rats and diabetic encephalopathy rats

In this study, we determined the neuroprotective effect of aucubin on diabetes and diabetic encephalopathy. With the exception of the control group, all rats received intraperitoneal injections of streptozotocin (STZ; 60?mg/kg) to induce type 1 diabetes mellitus (DM). Aucubin (1, 5, 10?mg/kg ip) was used after induction of DM (immediately) and diabetic encephalopathy (65?days after the induction of diabetes). The diabetic encephalopathy treatment groups were divided into short-term and long-term treatment groups. Treatment responses to all parameters were examined (body weight, plasma glucose, Y-maze error rates and proportion of apoptotic cells). In diabetic rats, aucubin controlled blood glucose levels effectively, prevented complications, and improved the quality of life of diabetic rats. In diabetic encephalopathy, aucubin significantly rescued neurons in the hippocampal CA1 subfield and reduced working errors during behavioral testing. The significant neuroprotective effect of aucubin could be seen not only in the short term (15?days) but also in the long term (45?days), which was a highly encouraging finding. These data suggest that aucubin may be a potential neuroprotective agent.     

Regeneration and transplantation of muscles in old rats and between young and old rats.

In order to compare the regenerative ability of skeletal muscle between young (5 month) and old (26 month) rats, sliced or intact extensor digitorum longus muscles were freely autografted into young and old rats and also reciprocally grafted from young to old inbred animals and vice versa. Sixty days after grafting, the transplants were analyzed for contractile and histochemical properties. There was a relative similarity between the contraction times of both normal control muscles and of all groups of transplants, although the contraction time tended to be prolonged and histochemical fiber pattern was more often found to be uniform in grafts of senescent animals. All groups of transplants possessed histochemically heterogeneous fiber types at 60 days. The experiments demonstrate that skeletal muscle in old rats possesses a substantial degree of regenerative ability and that the free tranpllantation of entire muscles in old animals is feasible.     

Experimental hypertriglyceridaemia and hypercholesterolaemia in rats

Lipid disorders and cardiovascular diseases have been related in many studies. We here studied the influence of acute ingestion of a long chain triglyceride (LCT) emulsion (rich in triglycerides) on plasma triglyceride (TG) and total cholesterol (TC) levels in laboratory animals (Wistar rats), comparing it with the induction of hypertriglyceridaemia and hypercholesterolaemia by Triton WR-1339 injection. The results show that Triton would be suitable for inducing hypercholesterolaemia but not hypertriglyceridaemias similar to those in humans. The LCT emulsion intake, however, provoked transitory hyperlipaemia with values similar to those often found in hyperlipaemic subjects, and would thus be suitable for testing possible antilipaemic treatments. Our study also presents a model of hypertriglyceridaemia, hypercholesterolaemia and obesity in experimental animals, provoked by a chronic intake of an LCT emulsion. This model may be useful in investigating the mechanisms of the pathogenesis of atherosclerosis and the pharmacological treatment of obesity and dyslipaemias.     

Amphetamine-induced overeating and overweight in rats

Female rats given a large dose of d-amphetamine displayed transient anorexia and loss of weight as one would expect. A week later, after their food intake and weight had returned to baseline, they began to overeat and gain weight. Within three weeks they were eating 7% more than normal. They became 3% overweight with a 5% increase in body fat. The hyperphagia persisted for two months. Thus amphetamine, an appetite suppressant and sympathomimetic drug, can cause prolonged hyperphagia and mild obesity with delayed onset following a single overdose.     

Atriopeptin and spontaneous hypertension in rats

The involvement of atriopeptin in hypertension was investigated in spontaneously hypertensive rats (SHR). It was found that intravenous injection of atriopeptin III (20-80 nmol/kg) markedly decreased the mean arterial pressure in anesthetized SHR in a dose dependent manner. The heart rate was not significantly affected. The contents of atriopeptin immunoreactive material in the rat atrium and plasma were measured with radioimmunoassay. Both the atrium and plasma contents of atriopeptin immunoreactive material were found to be significantly higher in SHR than in the normotensive control Wistar Kyoto (WKY), indicating an increase in the biosynthesis and release of atriopeptin in SHR. Whether this change was a compensatory response induced by hypertension remains to be investigated.     

Arginine vasotocin and aggression in rats

Pinealectomized (PX) and sham animals were administered either AVT (1 ng/kg) or vehicle (1 ml H₂O). Boxing-kicking-biting episodes were significantly reduced by administration of AVT, F(1,21)=8.09,p<0.009. Crawling under behavior was increased in PXH₂O animals (p<0.05). Non-aggressive rearing was decreased by administration of AVT, F(1,21)=4.75, p<0.04. These results are in agreement with previous findings that AVT lowers emotionality-arousal. Results are discussed in terms of vasotonergic effects on central monoamines.     

Haplotype-based genetics in mice and rats

Haplotype blocks are conceptually defined as genomic segments harbouring sets of coupled polymorphisms that reflect a common ancestral origin. Experimentally, however, haplotype blocks are characterized using computational algorithms based on incomplete inventories of polymorphisms. Haplotype blocks and their deduced strain-distribution patterns are considered to be extremely powerful for use in genetic association and mapping experiments in laboratory mice and rats. However, recent high-density SNP screening in commonly used mouse inbred strains reveals a complex pattern, suggesting that the current expectations for the use of haplotype blocks in genetic mapping will have to be revisited.