Variation in pentobarbitone sleeping time in mice 1. Strain and sex differences

Abstract

85Summary A set of 23 inbred strains of mice was tested for their sleeping time under sodium pentobarbitone anaesthetic. Highly significant strain differences were found. Estimates of the proportion of the variation accounted for by genetic differences ranged from 28% to 42%. In general, males slept longer than females but the size of the sex differences was not consistent across strains. Sleeping times on different test days also varied, indicating that environmental factors were affecting the results. A specially designed experiment failed to detect any differences in within-strain variation.

Variation in barbiturate sleeping time in mice 3. Strain × environment interactions

“…Although C57BL/6J was not one of the strains investigated in the earlier study both a related strain, C57BL/lOScSn, and BALB/c had shown the expected sex difference (Lovell, 1986a).…”

“…The method described earlier (Lovell, 1986a(Lovell, , 1986b was used. All mice were injected with 60 mg/kg pentobarbitone sodium (Nembutal Abbot Laboratories, Queenborough, Kent).…”

“…A large proportion of the total variation in pentobarbitone sleeping time (PST) in a sample of 23 inbred strains of mice was caused by genetic differences between the strains (Lovell, 1986a). PST was also affected by factors such as the age of the animal and the dose revel (Lovell, 1986b).…”

Observations on the use of medetomidine/ketamine and its reversal with atipamezole for chemical restraint in the mouse

“…Other authors have measured the duration of sleep time (duration of loss of righting reflex) between sexes and strains, but we could find no published data measuring the loss time. Male mice of several strains had longer sleep time than females after pentobarbitone (Brown 1959, Lovell 1986 or hexobarbitone (Rumke & Noordhoek 1969). Females had a tendency to sleep longer after intraperitoneal medetomidine-ketamine combination (Voipio et al 1988).…”

Variation in pentobarbitone sleeping time in mice 2. Variables affecting test results

“…bedding, painful stimuli and time of drug administration affected the hexobarbitone sleeping time (HST). In a previous paper (Lovell, 1986) strain and sex were shown to have a major effect on the PST. Descriptions of the environmental conditions that laboratory animals are held under are often inadequate ; this makes replication of experiments between laboratories difficult and complicates interpretation.…”