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Biomedical subjects

W R Schmidek

Publications and source records attributed to W R Schmidek.

8 recordsLinked to original sources
PubMed1988

Differences in individual rat preference for light levels.

Behavioral observations assessing the position of individual animals in relation to a light gradient have shown that rats have strong preference for environmental locations with reduced luminosity. Albino rats have a significantly greater darkness preference than a strain of hooded rats although no intersexual differences were detected. Individual animals show marked and stable differences in their darkness preference. These tendencies are already present in weanling rats and are maintained throughout development.

Animals↗
PubMed1986

Effect of xylocaine and carbachol applied to the caudate nucleus of rats on barbiturate sleeping time.

Since lesion of subcortical structures may affect the barbiturate sleeping time (bST), we decided with the present study to elucidate the role of the caudate nucleus in the determination of central sensitivity to barbiturates. Rats implanted with a cannula in the caudate nucleus of one or both sides, as well as with a jugular cannula, were utilized. Intravenous injections of sodium pentobarbital (40 mg/kg), intracerebral injections of Xylocaine (0.04 microgram), carbachol (0.2 micrograms) or artificial cerebrospinal fluid (ACF) into the caudate nucleus were performed. Both Xylocaine and carbachol, but not ACF, increased the bST regardless of the preparation used, the only exception being Xylocaine which did not alter the bST, if injected into the left caudate nucleus. The results suggest that the caudate nucleus may act as a modulator of the central sensitivity to barbiturates.

Animals↗
PubMed1984

Influence of ambient temperature on the sleep-wakefulness cycle in the golden hamster.

The sleep-wakefulness cycle (SWC) of euthermic golden hamsters (Mesocricetus auratus) after 5 weeks of warm (30 degrees C) and of cold (5 degrees C) acclimation, was recorded at ambient temperatures between 5 degrees and 35 degrees C. Significant influences both of acclimation and of recording temperature were detected. Amount of paradoxical sleep (P%) after warm acclimation was maximal at 30 degrees C decreasing markedly at lower and higher temperatures. Variations in P% were mainly consequent to alterations in the frequency of occurrence of paradoxical sleep (PS) episodes. After cold acclimation (CA) P% was maximal at 20 degrees C but no strong decreases occurred at lower temperatures. Influences of CA upon SWC were already detectable after 3 days of cold exposure. Significant individual differences as well as strong fluctuations in P% during CA occurred. Acute oscillations in abdominal temperature along the SWC were recorded. Reductions in abdominal temperature during PS episodes, in relation to ambient temperature and to the length of the episode tended to occur.

Acclimatization↗
PubMed1983

Total calorimetric measurements in the rat: influences of the sleep-wakefulness cycle and of the environmental temperature.

Rates of production as well as dry and evaporative heat loss during the sleep-wakefulness cycle were studied in 11 male, adult albino rats with chronically implanted electrodes and thermocouple re-entrant tubes. Two groups of animals chronically acclimated to 6 or 23 degrees C were acutely studied at 15, 20, 25, 30 and 35 degrees C. Statistical analysis of the data shows that rates of heat production and dry heat loss differ with respect to acclimation and acute environmental temperatures, and show significant differences depending on the states of the sleep-wakefulness cycle. Rate of heat production was highest during wakefulness, intermediate during synchronized sleep and lowest during paradoxical sleep. Rate of dry heat loss of 15 degrees C was maximal during paradoxical sleep. Rate of evaporative heat loss apparently did not change with the states of the sleep-wakefulness cycle. Heat storage estimated from difference in rates of heat production and heat loss was positive during wakefulness, slightly negative during synchronized sleep and markedly negative during paradoxical sleep. The data presented suggest a clear although partial suppression of thermoregulatory mechanisms during paradoxical sleep in the white rat.

Acclimatization↗
PubMed1983

An inexpensive event recorder for continuous behavioral recording.

An event recorder for use in ethological studies which is of simple and inexpensive construction is described. The apparatus consists essentially of a constant speed paper transport device and an ethogram sheet holder. Up to 20 different behavioral items may be recorded continuously in an accurate time sequence. The items are coded as hand-drawn pencil lines of different length perpendicular to the direction of the paper movement. Since the ethogram code sheets are exchangeable, an unlimited number of different ethograms may be used.

Animals↗