Rat Strain Differences in the Acquisition of Conditioned Avoidance Responses and in the Effects of Diazepam

Abstract

Abstract-Adult male albino rats of three strains-Wistar, Sprague-Dawley and Holtzman-were trained to press a lever to avoid electric shocks under Sidman-type (R-S interval=20 sec; S-S interval=5 sec) and discriminated avoidance (ITI=15 sec; warning duration=5 sec) schedules, and the acquisition processes of avoidance re sponses, and the properties of behavioral baselines were investigated. Under both schedules, Wistar strain rats, though showing poorer results than the other two in the beginning, rapidly progressed with the repetitive training, and finally displayed excellent and stable performances.Sprague-Dawley strain rats were poorer in performances, with delayed acquisition and prolonged warm-up effect in the within-session perfor mance. The results of Holtzman strain rats ranked between the two. After the establishment of stable behavioral baselines under both schedules, 0.5, 1.0 and 2.0 mg/kg of diazepam were given subcutaneously, and it was found that in Wistar and Holtzman strain rats, the avoidance responses were inhibited together with increase of delivered shocks in parallel to the doses. In Sprague-Dawley strain rats, however, the avoidance responses were conversely improved with 0.5 and 1.0 mg/kg, while such tended to be inhibited with 2.0 mg/kg, with marked concomitant ataxia. As definite strain differences in avoidance response were demonstrated herein, selection of the most appropriate strain should be made when designing behavioral experiments.In experiments with laboratory rats, differences by strains are sometimes observed in physiological and biochemical phenomena (1), or in behavioral phenomena such as emotion ality, spontaneous motor activity and acquisition process of conditioned behavior (1-6).On the other hand, it has been reported (7-13) that in assaying psychotropic drugs be haviorally, the effects are greatly affected by the behavioral baselines in the pre-drugged state.The present work revealed marked difference by strains of rats not only in the acquisition processes of conditioned avoidance responses and in the behavioral baselines established but also in the sensitivities to diazepam. The present work is considered significant, since the avoidance responses are used extensively in the study of psychotropic drugs. MATERIALS AND METHODSSubjects: Experimental animals were adult male albino rats of three strains-Wistar (W), Sprague-Dawley (S) and Holtzman (H)-obtained from the breeding room of Medical School, Gunma University. W-strain rats have been bred by brother-sister mating for more than 20 years. All were fed a solid diet MF (Oriental Yeast Co., Tokyo) and given tap water ad libitum.

Disturbance of retention of memory after focal cerebral ischemia in rats.

“…Kuribara et al 19 reported interstrain differences in the acquisition of conditioned avoidance responses in the rat, and Kuribara 11 also showed that Fischer-strain rats can successfully perform active avoidance tasks. It was reported that MCA occlusion in the Fischer-344 rat showed the most reproducible infarct volume among various strains tested.…”

Strain, sex, and open-field behavior: Factors underlying the genetic susceptibility to helplessness

“…However, naïve Holtzman rats are capable of achieving 100% efficiency when trained to press a lever to escape shock [7] and they have superior acquisition of an avoidance response when compared to two other albino strains (Wistar and Sprague Dawleys) [19]. Therefore, there is no evidence in the existing literature to suggest deficits in the Holtzman strain’s pain perception or general learning ability.…”

Mother–infant separation leads to hypoactive behavior in adolescent Holtzman rats

“…In the same study, administration of antidepressant drugs increased the amount of reinforcements received by HO rats but had no effect on SD rats. Another study reported that HO differed from Wistar and SD strains for conditioned avoidance and that diazepam affected the avoidance behavior of HO rats differently than SD rats -low levels of diazepam inhibited the avoidance response in HO rats while enhancing it in SD rats (Kuribara et al, 1976). Similarly, chemical lesions of the catecholaminergic system resulted in differing ethanol consumption rates -no change in HO rats, but decreased consumption in SD rats (Melchior et al, 1976).…”