The susceptibility of albino and gray Norway rats to audiogenic seizures.

Abstract

In experiments on audiogenic seizures, we have tested by air blast two strains of inbred rats, the Wistar albino and gray Norway. The latter strain showed, on the average, a decidedly greater frequency of attacks. Analysis of the individual records demonstrated a preponderance of highly susceptible animals among the gray Norways.Rats in these two strains exhibit marked differences in temperament and behavior. The inherited wildness and savageness of gray Norway rats is well known (1,2,3). Gray rats, in order to be made manageable for experimentation, require a regime of handling begun before weaning, which nevertheless does not completely eradicate their innate wildness. It seems likely that the high incidence of audiogenic seizures in gray Norway rats is related in some way to their temperament.

Convulsive behavior in the rat.

“…The question of the relation between severity of attack and age is not clearly settled. In younger rats the seizures seem to be principally of the running type, with the more severe convulsions appearing more frequently with age increment (34,130). Smith (153), however, reports more deaths during seizure in the younger subjects.…”

“…The exact time relations will undoubtedly vary from investigation to investigation, depending on such uncontrolled factors as diet, strain of rat, mode of testing, etc. For example, the same experimenters (34) find that in gray Norway rats the percentage of attacks increases up to the age of 80-100 days. ment a supplement of vitamin B-complex concentrate is given, the more complete the protection against sound-induced seizure (128).…”

“…Morgan (119) found no reliable difference in the average latency of audiogenic seizure between the two sexes, and no statistically significant differences in over-all incidence has been reported (e.g., 7), But in spite of the lack of conclusive data in any single study, the trend of all available figures is in the same direction--slightly more males than females respond convulsively during auditory stimulation. Unpublished data of the writer show 18.7% of 268 unselected males and 11.6% of 112 females susceptible over a series of four tests, Maier and Glaser (102) report 55.7% vs. 52.3%, and Farris and Yeakel (34) and Finger (39) found differences of a similar order, Farris and Yeakel (33) suggest that males may react more frequently early in life, with responses of females predominating later. Although females might logically be expected to be more variable in their response because of their periodic physiological changes, it is impossible without further experimental data to assign greater total susceptibility to either sex.…”

“…Because of the apparent primacy of the auditory component in inducing the convulsive reaction, Morgan and Waldman (123) suggested the descriptive phrase "audiogenic seizure," which has become the most widely accepted term. 6 The audiogenic seizure is influenced in both its pattern and frequency of occurrence by a number of secondary factors, so that susceptibility figures within a colony and in a particular testing situation range from 10% or less (86,122) to well over 90% (34). The inhibiting effect of the following factors has been demonstrated: strenuous activity before or during the stimulation period (2,76,101); extreme restriction of movement (54,88); the establishment of position habits (103) or the development of abortive jumping (93) when the stimulation is in the Lashley apparatus; the appearance of a fear reaction (2); previous exposure to the convulsion-producing sound (11,38,76,99,153); electrification of the floor during the auditory stimulation (15); the provision of a "psychological shelter" (56); taming (76); temperature changes (101); chronic "emotionality" (11,114); vagotomy (88); partial curarization (88); and the administration of such substances as adrenin (2,87), dilantin sodium (21,54,148), adrenal cortex (54), thiamin hydrochloride (59,81), atropine (72,73), B-complex vitamins and minerals (131,133,134).…”

“…The frequency or severity of seizure has been found to be increased by such means as repeated anger stimulation (163,164); increased intensity of auditory stimulation (48,120,121); chronic disturbances induced in other situations (75,76); increased conflict, e.g., as provided by additional barriers to escape (99,103); cutaneous stimulation furnished by water spray (97); temporary deprivation of food and drink (38); lactation (127); perhaps prenatal treatment with sodium bromide (64); B-complex avitaminosis (133); magnesium deficiency (135); and injection of subconvulsive doses of strychnine (2,153,154), metrazol (78,103,106,145,154), caffeine sodium benzoate (154), sodium phosphate (50), and coramine (166). Age differences (31,33,39,102), sex differences (33), genetic background (34,39,57,58,95,100,113), blood composition (86), inanition (132), cortical insult (7,153,169), punishment for seizure (107), and eserine (72,…”