Studies of abnormal behavior in the rat. XI. Factors that influence the type of reaction to metrazol.

Abstract

Previous studies having indicated that there are 2 distinct types of convulsive response to the injn. of metrazol in the rat, the present study was undertaken to evaluate some of the factors responsible for these 2 types of response. Two "largely inbred" strains (one yielding a high and the other a low proportion of animals susceptible to seizures) were investigated, and the strain differences noted in the response to metrazol appear significant. After a series of metrazol-induced convulsions (weekly injns.) the convulsant-threshold for metrazol is depressed and stabilized while the convulsive pattern becomes more elaborate. Similar effects are observed to result from repeated convulsive seizures, and exposure to the auditory situation without seizure seems to result in similar but less effective changes. "It is concluded that the instability of the unstable strain is general, rather than specific for either auditory stimulation or metrazol." Since differences between strains seemed more important than differences between individuals who were and who were not susceptible to seizures, "it is therefore concluded that instability in auditory situations and in metrazol reactions are related but independent hereditary factors.".