| The Norway rat or Rattus
norvegicus, is a mammal in the order Rodentia. Rattus norvegicus
apparently originated in Asia and then spread throughout most of the
world in close association with humans. Although the species does exist
in Norway, this element of the name has no particular
significance. Rattus norvegicus may have reached Europe
around 1700, England about 1730, and the New England area of the U.S.
at about the time of the Revolutionary War [Lindsey, 1979].
All laboratory rats are domesticated strains of R. norvegicus. In fact, R. norvegicus was the first animal where the primary reason for domestication was for use in scientific endeavors. Breeding experiments date to about 1880, with laboratory research using rats commencing shortly thereafter in the U.S. The early laboratory stocks were mostly bred from albino animals that had originated as wild mutants, which of course still occur in wild populations of R. norvegicus. Much of the earliest research with laboratory rats dealt with nutrition. Laboratory rats were first used in behavioral research in 1895 in a study of the effects of alcohol, diet, and barometric pressure on activity levels conducted at Clark University [Lindsey, 1979]. Rats can be
grouped by their microbial colonization: Specific Pathogen Free (SPF)
rats are free from known bacterial, viral, and parasitic rat pathogens,
as opposed to "conventional" rats, which are not known to be free of
pathogens. The rats purchased at CSUB are SPF, but the standard housing
cannot totally prevent the introduction of rodent pathogens. Rats can
also be categorized genetically. Common genetic categories are
"random-bred" rats which are managed to maintain genetic diversity by
mating unrelated rats; "Inbred" rats, which are managed to maintain
genetic homozygosity by breeding siblings; and "F1 hybrid rats," which
are produced by crossing two inbred strains for one generation. |