Inbred Strains
of Rats: MR
Inbr.F86 (Pit).
Colour: Albino
Genet. a, c, h.
Origin: as for MNR except selection was for high defecation response in
the open field. To Harrington in 1965 at F25 and to NIH in 1964 at F18+
(Hansen et al 1982).
Characteristics
Compared with MNR, the strain has a high open-field defecation, low ambulation,
low rearing, low shock avoidance conditionability and tends to be more
"emotional" in a wide range of behaviour (
Broadhurst
1975), and have a higher preference for ethanol (
Brewster
1968). Also differs from MNR in norepinephrine concentration in hypothalamus,
heart, spleen and adrenal glands, suggesting that the sympathetic system
might be functionally related to behavioural differences between the
strains (
Liang and Blizzard 1978). Lower
specific benzodiazepine binding than MNR in hippocampus, hypothalamus,
midbrain, medulla/pons and spinal cord, which might be a biological basis
for differences in emotional behaviour (
Robertson
et al 1978). Long emergence latency in a novel environment in females
(12/12) and also into a familiar environment in males (11/12) (
Harrington
1971a). High open field defecation (1/12 males 2/12 females) (
Harrington
1972). Shows substantial habituation to acoustic startle stimulous
(
Commissaris et al 1988). mRNA and
protein populations in the brains of MR and MNR have been studied by Whatley
et al (
1992).
Good breeding performance (4/12) and large litter size (2/12) (Hansen et al 1973).
See also MNR.
Brewster D. J.
(1968) Genetic analysis of ethanol preference in rats selected for emotional
reactivity. J. Hered. 59, 283-286.
Broadhurst
P. L. (1975) The Maudsley reactive and non-reactive strains of rats: a
survey. Behav. Genet. 5, 299-319.
Commissaris
R. L., Harrington G. M., Baginski T. J., and Altman H. J. (1988) MR/Har
and MNRA/Har Maudsley rat strains: differences in acoustic startle habituation.
Behav. Genet. 18, 663-669.
Hansen
C. T., Judge F. J., and Whitney R. A. (1973) Catalogue of NIH Rodents.
DREW Publ. No. 74-606. Department of Health, Education, and Welfare,
Washington, D.C.: U.S.
Hansen
C. T., Potkay S., Watson W. T., and Whitney R. A. Jr. (1982) NIH Rodents:
(1980). Catalogue. NIH Publ. No. 83-606. Department of Health and
Human Services, Washington, D.C.: U.S.
Harrington
G. M. (1971a) Strain differences among rats initiating exploration of
differing environments. Psychon. Sci. 23, 348-349.
Harrington
G. M. (1972) Strain differences in open-field behavior of the rat. Psychon.
Sci. 27, 51-53.
Liang B.
and Blizard D. A. (1978) Central and peripheral norepinephrine concentrations
in rat strains selectively bred for differences in response to stress:
Confirmation and extension. Pharmacol. Biochem. Behav. 8,
75-80.
Robertson
H. A., Martin I. L., and Candy J. M. (1978) Differences in benzodiazepine
receptor binding in Maudsely reactive and Maudsely non-reactive rats.
Eur. J. Pharmacol. 50, 455-457.
Whatley
S. A., Perrett C. W., Zamani R., and Gray J. A. (1992) Analysis of relative
messenger-RNA levels and protein-patterns in brains of rat strains bred
for differing levels of emotionality. Behav. Genet. 22,
403-413.
INBRED STRAINS OF RATS
Updated 9 Apr. 1998
Michael FW
Festing
MRC Toxicology Unit, Hodgkin Building,
University of Leicester,
UK
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