Physiology & behavior
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Physiology & behavior · Jun 2005
Comparative StudyBasal and carrageenan-induced pain behavior in Sprague-Dawley, Lewis and Fischer rats.
Individual differences in pain sensitivity are believed to reflect the interplay of many factors, including genetics. Inbred rat strains can be used to study the impact of genetic factors on pain sensitivity. Inbred Lewis (LEW) and Fischer 344 (FIS) rat strains display profound and contrasting alterations in neuroendocrine, immunological and behavioral responses to stressors. ⋯ Hindlimb muscle grip force and tail-flick latencies did not differ across the three strains, either before or after carrageenan. These results demonstrate differences in basal and carrageenan-induced pain sensitivity in LEW, FIS and SD rats, which extend earlier findings that genetic factors modulate both basal and inflammatory pain. The results further demonstrate that basal pain sensitivity can be predictive of inflammatory pain sensitivity, with the direction of the effect dependent upon the pain measure.
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Physiology & behavior · Mar 2005
Comparative StudyBrain and body temperature homeostasis during sodium pentobarbital anesthesia with and without body warming in rats.
High-speed, multi-site thermorecording offers the ability to follow the dynamics of heat production and flow in an organism. This approach was used to study brain-body temperature homeostasis during the development of general anesthesia induced by sodium pentobarbital (50 mg/kg, ip) in rats. Animals were chronically implanted with thermocouple probes in two brain areas, the abdominal cavity, and subcutaneously, and temperatures were measured during anesthesia both with and without (control) body warming. ⋯ These results suggest that pentobarbital-induced inhibition of brain metabolic activity is a major factor behind brain hypothermia and global body hypothermia during general anesthesia. These data also indicate that body warming is unable to fully compensate for anesthesia-induced brain hypothermia and enhances the negative brain-body temperature differentials typical of anesthesia. Since temperature strongly affects various underlying parameters of neuronal activity, these findings are important for electrophysiological studies performed in anesthetized animal preparations.
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Physiology & behavior · Jan 2005
Randomized Controlled Trial Clinical TrialEffects of transdermal nicotine on prose memory and attention in smokers and nonsmokers.
Previous research investigating cognitive effects of nicotine has produced mixed findings partly due to the use of abstaining smokers and cigarettes as a delivery system. The present study examined effects of nicotine delivered via a transdermal patch on prose memory and sustained attention in male smokers (n=25) and nonsmokers (n=22), who were randomly assigned to either a placebo or a nicotine condition. All groups were matched on their verbal ability and gross personality characteristics (state/trait anxiety levels, extroversion-introversion, and impulsivity level). ⋯ No between-group differences were found on the RVIP task. A significant effect of time was found for systolic blood pressure and heart rate. The results cannot be interpreted using the arousal theory of nicotine effects on attention and are explained on the basis of a dose-dependent nicotinic action possibly recruiting cholinergic cortical projections.
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Physiology & behavior · Jan 2005
Recording of ECG signals on a portable MiniDisc recorder for time and frequency domain heart rate variability analysis.
Analysis of heart rate variability (HRV) is a non-invasive technique useful for investigating autonomic function in both humans and animals. It has been used for research into both behaviour and physiology. Commercial systems for human HRV analysis are expensive and may not have sufficient flexibility for appropriate analysis in animals. ⋯ IBI data were analysed in both time and frequency domains and comparisons between direct recorded and MiniDisc data were made using Bland-Altman analysis. Despite some changes in ECG morphology due to loss of low frequency content (primarily below 5 Hz) following MiniDisc recording, there was minimal difference in IBI or time or frequency domain analysis between the two recording methods. The MiniDisc offers a cost-effective approach to intermediate recording of ECG signals for subsequent HRV analysis and also provides greater flexibility than use of human Holter systems.
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Physiology & behavior · Dec 2004
Comparative StudyOpioid-mediated pain sensitivity in mice bred for high voluntary wheel running.
We tested the hypothesis that thermal tail-flick latency, a common measure of pain sensitivity in rodents, would be altered in lines of mice that had been selectively bred for high voluntary wheel-running behavior. Specifically, we predicted that the selected (High-Runner) lines would show decreased pain sensitivity relative to their control (C; randombred) lines, and would respond differently to drugs that block opioid receptors. We first compared tail-flick latency between High-Runner and C female mice during the day (no wheel access) and at night (with wheel access). ⋯ Administration of naloxone (10 mg/kg, i.p.) decreased tail-flick latency measured during the day, equally in High-Runner and C mice. Naloxone (5 and 10 mg/kg, i.p.) and high doses of naltrexone (50 and 100 mg/kg, i.p.) decreased wheel running equally in High-Runner and C mice. Further studies will be required to determine whether other types of pain sensitivity have also failed to evolve in association with increased voluntary wheel running.