Short-sleep Line Research Articles

Propofol produces differences in behavior but not chloride channel function between selected lines of mice.

We report differential central nervous system (CNS) sensitivity to propofol between Long Sleep (LS) and Short Sleep (SS) mice, selectively bred for their differential CNS sensitivity to ethanol. Intravenous propofol requirements for loss of righting reflex, or sleep time, were measured to define the extent of this sensitivity. LS mice slept approximately two times longer than SS mice at equal doses. Awakening plasma and brain levels of the SS line were, respectively, two and three times that of the LS line (P < 0.0001). This suggests that the LS and SS sleep time difference is CNS mediated, and that propofol and ethanol may share common genes that determine anesthetic sensitivities. The ethanol effect may be at least partially mediated by gamma-aminobutyric acid-A (GABAA) receptor function. Propofol had no differential effect on GABAA receptor function, as measured by chloride flux in LS and SS brain microsac preparations. Either the GABAA receptor does not mediate propofol sleep time, or qualitative differences cannot be demonstrated using 36Cl- uptake in brain membranes.

Comparisons of subcolonies of selectively bred long-sleep and short-sleep mice.

The Albany subcolony of the selectively bred Long- and Short-Sleep mice was directly compared to the original Colorado colony. As expected from the additional selection applied to the Colorado colony, small differences in the selection phenotype, loss of the righting reflex duration following ethanol treatment, were observed in the Short-Sleep line. However, no colony differences existed in three other indices of ethanol effects. Clear line differences in the shape of the locomotor activity dose-response curve, thermoregulatory effects of ethanol, and ethanol elimination rate replicated earlier findings, but these differences were similar in the two colonies. These data argue for stability of the polygenic control system and provide a picture of remarkable similarity of the two sublines, which were separated by more than 30 generations.

Divergent selection for pentobarbital-induced sleeping times in mice.

A pharmacogenetic model for sensitivity of mice to pentobarbital is being developed by selection for sleep-time response. One generation of divergent selection for long and short sleep-time in mice resulted in a 19% increase in the long-sleep line and a 15% decrease in the short-sleep line. Calculated heritability estimates averaged 0.49 and realized heritabilities averaged 0.24. The extent of the selection progress and the heritability values indicate that genetic constitution plays a major role in controlling variations of sleep-time response to pentobarbital.

Hormonal Tolerance to Ethanol is Associated with Decreased Expression of the GTP‐Binding Protein, Gsα, and Adenylyl Cyclase Activity in Ethanol‐Treated LS Mice

Using the proopiomelanocortin (POMC) system as a marker, long sleep (LS) and short sleep (SS) lines of mice were investigated to explore the cellular events that occur during the acquisition of hormonal tolerance to ethanol. Four-day ethanol exposure (1.8 g/kg/24 hr) increased anterior pituitary POMC mRNA levels 4-fold in the LS line and 2-fold in the SS line. Following 7 days of ethanol exposure (1.8 g/kg/24 hr), anterior pituitary POMC levels returned to basal values in the LS line but remained elevated (2-fold) in the SS line. In this setting, the loss of ethanol's ability to sustain elevated POMC mRNA levels in the LS line is defined as hormonal tolerance. Since POMC biosynthesis is primarily regulated through adenylyl cyclase, ethanol-induced alterations in this signal transduction system were explored. Paralleling the effects of ethanol on POMC mRNA levels, ethanol exposure reduced GTP-gamma-S, AIF3-, and MnCl2-stimulated adenylyl cyclase activity by 35%, 21%, and 24%, respectively, in the LS line without effecting adenylyl cyclase activity in the SS line. To determine whether ethanol-induced changes in adenylyl cyclase activity in LS mice could result from alterations in G proteins, protein levels of G, alpha and Gi alpha were determined by western analysis before and after ethanol exposure. Paralleling the effect on POMC mRNA levels and adenylyl cyclase activity, ethanol induced a 35% reduction in Gs alpha protein levels in LS mice but did not alter Gi alpha levels. Neither Gs alpha nor Gi alpha levels were altered in the SS line.(ABSTRACT TRUNCATED AT 250 WORDS)

Distinctions among sedative, disinhibitory, and ataxic properties of ethanol in inbred and selectively bred mice

Three different domains of behavioral action of ethanol (ETOH) were examined in a battery of seven inbred strains and in the selectively bred Long-Sleep (LS) and Short-Sleep (SS) mice. Sedative effects were examined with the loss of the righting reflex test at 3.8 g/kg. The variation among inbred strains was only half the size of the difference between LS and SS mice which were selectively bred for extremes in this phenotype; such a result is expected for phenotypes controlled polygenically. Blood ETOH levels at waking from the narcosis also showed a range of differences among the inbred strains that was less than the LS/SS difference. Ataxia was measured with the grid test, and the inbred strains fell into two groups, resembling the highly ataxic LS line, and the less ataxic SS line. Biphasic effects of ETOH on locomotor activity were strongly genotype dependent. Variation in degree of activation/disinhibition produced by doses up to 1.5 g/kg (IP) ranged from no activation, in the C57BL/6Abg strain which was larger than that seen for SS mice. The patterns of strain differences for both ataxia and activation were highly different from the duration of loss of righting reflex measure, suggesting multiple independent genetically based "sensitivities" to ETOH.

Differential response to flurazepam in long-sleep and short-sleep mice

In addition to differing in ethanol sensitivity, long-sleep (LS) and short-sleep (SS) mice also differ in response to GABAergic agents. In the present study the sensitivity of LS and SS mice to the anesthetic, hypothermic and anticonvulsant effects of benzodiazepine, flurazepam, was determined. Flurazepam (75–300 mg/kg) induced a dose-dependent loss of righting response in both lines. The LS line displayed a two-fold greater sensitivity to the anesthetic effects of flurazepam. A dose-dependent decrease in body temperature was also observed following administration of flurazepam (25–150 mg/kg), but the two lines did not differ on this measure. Determination of the anticonvulsant effects of flurazepam (1–6 mg/kg) against seizures induced by 3-mercaptopropionic acid revealed that the SS line was more sensitive to the anticonvulsant effects of this benzodiazepine. These studies demonstrate that LS and SS mice differ in response to flurazepam, but the nature of the difference depends on the type of response measured and the dose of flurazepam employed.

Sedative-hypnotic anomalies related to dose of pentobarbital in long-Sleep and short-sleep selectively-bred mice

Hypnotic effects following administration of three doses of pentobarbital were evaluated in mice selectively-bred for differential hypnotic sensitivity to ethanol. Although the ethanol-sensitive Long-Sleep (LS) line displays greater sedation to a wide variety of CNS depressants (alcohols, barbiturates, benzodiazepines, general anesthetics), when compared to the ethanol-insensitive Short-Sleep (SS) line, the response pattern to pentobarbital remains equivocal. Thus, to clarify the effect of pentobarbital, certain variables (dose, sex, circadian rhythmicity) believed to be important in the expression of sleep time were evaluated. For all doses examined “sex” and “time of day tested” impacted on sleep time. With these provisos, 40 mg/kg consistently induced shorter sleep time in SS mice. The 60 mg/kg dose either failed to distinguish these two lines, or induced greater sleep times in the SS mice. The 80 mg/kg dose tended to have the same effect as the 60 mg/kg dose, but to a greater degree. Overall, it appears that for each line the dose response curve for pentobarbital is sigmoidal, but that the slope of the curve for the middle range of doses is greater for the SS line. Since pentobarbital has a unique effect on these lines of mice that is dissimilar to those reported for other barbiturates, the implication is that an additional factor, that is unimportant for other barbiturates, is essential for pentobarbital-induced hypnosis. Factors that could be responsible for this effect include differential metabolism or Gabaergic receptor dynamics.

Ethanol-induced grooming in mice selectively bred for differential sensitivity to ethanol

In rats, excessive grooming follows the application of several forms of stress. The injection of alcohol may be considered as a stressor, since it increases plasma corticosterone levels. The present study examines the effects of ethanol injections on grooming in two lines of mice selected for differences in their hypnotic response to ethanol, i.e., the long sleep (LS) and short sleep (SS) lines developed at the Institute for Behavior Genetics at the University of Colorado at Boulder. Various subhypnotic doses of ethanol produced excessive grooming in the SS line, but this did not occur in the LS line. The SS mice also displayed more "novelty-induced" grooming compared to the LS mice after repeated exposure to the testing situation. The increase in excessive grooming in both the ethanol-induced and the novelty-induced excessive grooming situations was most apparent in the second half of the observation period.

Genetic differences in reproductive fitness and offspring viability in mice exposed to alcohol during gestation

The effect of prenatal exposure to alcohol was studied in two lines of mice selectively bred for different sensitivities to alcohol: the long-sleep (LS) and short-sleep (SS) lines. LS females took longer than SS females to be come pregnant. Fewer LS offspring survived, even when not treated with alcohol. Although LS females tended to consume smaller doses of alcohol, offspring of LS dams consuming alcohol during the second half of gestation survived considerably less than 50% of the time. No such effect was seen in the SS line. These results are in agreement with others, indicating a line difference in several aspects of alcohol sensitivity.

Salsolinol differentially affects mice selected for sensitivity to alcohol.

Salsolinol, a compound putatively formed following alcohol ingestion, differentially decreased the activity of lines of mice after 18 generations of genetic selection for alcohol sensitivity. Low doses of salsolinol produced significantly lower activity levels in the alcohol-sensitive long-sleep (LS) line than in the alcohol-insensitive short-sleep (SS) line. A hypnotic dose of salsolinol induced significantly longer sleeptimes in the LS line than in the SS line. Results are interpreted as supporting the hypothesis that salsolinol-like substances may mediate some of the effects of alcohol on the central nervous system.