Role of autonomic nervous system for development and suppression of motion sickness in Suncus murinus.

To clarify the role of autonomic nervous function in motion sickness, the effect of agents that act on the autonomic nervous system on the motion stimuli-induced emesis was studied in two strains of Suncus murinus (Jic:SUN-Her and Jic:SUN-Ler) with congenitally different sensitivity to veratrine sulfate. We demonstrated significant differences between the two strains in sensitivity to motion stimuli. Isoproterenol (2.5 mg kg(-1), s.c.) significantly prolonged the latency to the first emetic episode induced by motion stimuli and significantly decreased the number of emetic episodes in Jic:SUN-Her suncus. Hexamethoium (2.0 mg kg(-1), s.c.) tended to shorten the latency in Jic:SUN-Ler. Acetylcholine (1.2 mg kg(-1), s.c.) enhanced the emetic response in Jic:SUN-Ler, but atropine (4.0 mg kg(-1), s.c.) suppressed motion stimuli-induced emetic response in Jic:SUN-Her. These results suggest that the predominance of parasympathetic nervous activity is relevant to the enhancement of motion stimuli-induced emetic response, whereas the predominance of sympathetic nervous activity suppresses motion stimuli-induced emetic response. Norepinephrine (0.8 mg kg(-1), s.c.) enhanced motion stimuli-induced emesis contrary to isoproterenol in Jic:SUN-Ler although both drugs are adrenergic agents. However, atropine pretreatment (4.0 mg kg(-1), s.c.) inhibits norepinephrine-induced emetic response. It was considered that norepinephrine-induced emetic response might be dependent on a secondary increase of parasympathetic nervous activity due to bororeflex. Moreover, the different emetic response in Jic:SUN-Her and Jic:SUN-Ler suncus to motion stimuli and drug administration mentioned above indicated that different participation of autonomic nervous activity and/or afferent information from the baroreceptor in the emetic response may exist between these animal groups.

Isolation and characterization of Helicobacter species from the stomach of the house musk shrew (Suncus murinus) with chronic gastritis.

A Gram-negative, motile bacterium with bipolar sheathed flagella (one at each end) was isolated from the stomach of house musk shrews (Suncus murinus) with chronic gastritis. The isolates grew at 37 degrees C under microaerophilic conditions, but not under aerobic conditions; rapidly hydrolyzed urea; were catalase, oxidase, alkaline phosphatase, and arginine aminopeptidase positive; reduced nitrate to nitrite; and were resistant to cephalothin and nalidixic acid, but sensitive to tetracycline, erythromycin, and chloramphenicol. This bacterium was found on gastric epithelial cells by electron microscopy. In addition, a coccoid form of the bacteria was found in vacuoles formed in the epithelial cells of some of the house musk shrews tested. These results, including 16S rRNA gene sequence analysis, strongly suggested that this bacterium should be classified as a novel Helicobacter species. It is proposed that this bacterium should be called "Helicobacter suncus."

Sedative effect of medetomidine and its reversal by atipamezole in house musk shrews (Suncus murinus).

This study was undertaken to evaluate the sedative effect of medetomidine, an alpha 2-adrenoceptor agonist, and the counteractive effect of atipamezole, an antagonist to medetomidine, in house musk shrews (Suncus murinus). Two hundred, 300, 400, or 600 micrograms/kg of medetomidine was intraperitoneal injected into 89 house musk shrews. A sedative effect was produced in one to two minutes after injection. The dose-dependent prolongation of the sedative duration and the dose-dependent appearance of a hypothermic effect were demonstrated. With 200 micrograms/kg of medetomidine, the sedative effect obtained was not adequate in some of the animals. With 300 micrograms/kg and above, a stable sedative state was induced in all the animals. The duration of sedation in the house musk shrews was much longer (p < 0.01) in males than in females. This suggested the higher susceptibility of male house musk shrews to this drug. The sedative effect and hypothermia obtained with 400 micrograms/kg of medetomidine were completely counteracted by more than 2.0 mg/kg of atipamezole. With 0.5 and 1.0 mg/kg of atipamezole, only a partial antagonistic action was produced. Transient vomiting appeared in 4.5% of the house musk shrews at approximately one minute after injection of medetomidine. This side-effect had occurred before the sedative effect was obtained, and was not serious enough to be a problem. None of the 89 house musk shrews died in this experiment. The above results show that the combination of medetomidine and atipamezole is a highly effective and safe anesthetic treatment which permits easy handling of house musk shrews.

Characterization of mycoplasma strains isolated from house musk shrews (Suncus murinus) and their infectivity in mice and rats.

Five mycoplasma strains isolated from house musk shrews (Suncus murinus) in the Central Institute for Experimental Animals were characterized and compared with three murine mycoplasma strains, Mycoplasma pulmonis m 53, M. arthritidis PG6, and M. neurolyticum Type A, and with reference strain G3-5 previously isolated from a house musk shrew. These isolates fermented glucose, but did not hydrolyze urea and arginine, passed through membrane filters of 450 nm pore size, were sensitive to digitonin, and formed minute (115 to 231 microns in diameter) colonies on agar medium. All the five unclassified house musk shrew mycoplasma strains and strain G3-5 used as a reference constituted a homogeneous group based on (i) their antigenic properties (determined using the metabolism inhibition test), (ii) their polypeptide profiles (determined using sodium dodecyl sulfate-polyacrylamide gel electrophoresis and the Western blotting assay), and (iii) their genomic properties (determined using DNA cleavage pattern analysis), but were quite distinct from the established murine mycoplasmas on the basis of these findings. In a survey of 56 house musk shrews aged 2 to 45 weeks in our colonies, mycoplasmas were isolated from the oral cavities of all animals examined. No gross or microscopic lesions were observed in the five animals from which the mycoplasma strains were isolated. In experimental infection, the mycoplasma was not infective for mice and rats. The results suggest that this group of mycoplasmas is a common inhabitant of house musk shrews.

[Diurnal rhythms in locomotor activity of the house musk shrew, Suncus murinus].

A diurnal rhythm of locomotor activity in male and female house musk shrews (Jic:SUN) aged approximately one year was observed under a schedule of 12 hr light and 12 hr darkness (light on at 07:00) over a period of 10 days. In general, the pattern of locomotor activity was similar in both sexes, with around 24-hr diurnal rhythm. A few typical patterns of locomotor activity in these animals were as follows: A. Locomotion interval was close in the light phase, while was sparse in the dark phase. B. As opposed to the pattern of A, locomotion interval was close in the dark and sparse in the light phases. C. Its interval remains stationary through a whole day.

[Diurnal rhythm of drinking activity in the house musk shrew].

A diurnal rhythm of drinking activity in 7 male and 6 female house musk shrews (Jic: SUN) aged about one year was observed over a period of 10 days under a schedule of 12 hr light and 12 hr darkness (light on at 07:00). In general, the pattern of drinking activity was similar among both sexes, with around 24-hr diurnal rhythm. A few typical drinking patterns of these animals were represented as follows: 1) Drinking interval was very close in the dark phase, while it was a little too sparse in the light phase (n = 4). 2) Its interval remains stationary through a whole day (n = 5). 3) Drinking was performed between the latter half of light and the first half of dark phases (n = 4).

[Laboratory breeding of the red-backed vole (Clethrionomys rufocanus bedfordiae)].

Laboratory matings were attempted to establish breeding colonies of red-backed voles (Clethrionomys rufocanus bedformidae) as experimental animals. For these mating, 10 pairs of red-backed voles which were captured in the Tohbetsu region of Hokkaido, Japan and their litters were used. In the results for two years, 1987 to 1988, the rates of pregnancy, birth and weaning were 35.4%, 94.5% and 79.5%, respectively. The mean litter size was 5:1 +/- 1.6 with a range of 1 to 9. The mean gestation period was 20.0 +/- 0.7 days with a range of 18 to 22. These results suggest that planned production of red-backed voles in the laboratory is possible. To determine intraregional variations of red-backed voles with a view to the establishment of a strain by inbreeding, restriction patterns of mitochondrial DNAs using seven restriction endonucleases were compared. Four different patterns were obtained from wild red-backed voles used in the present study.