Psychopharmacology 53, 213-215 (1977) Psycho pharmacology 9 by Springer-Verlag 1977 Impairment of Retention of Avoidance Responses in Rats by Posttraining Diethyldithiocarbamate C. W. SPANIS*, J. W. HAYCOCK, M. J. HANDWERKER, R. P. ROSE, and J. L. MCGAUGH Department of Psychobiology, School of Biological Sciences, University of California, Irvine, California 92717, U.S.A. Abstract. Diethyldithiocarbamate (680 mg/kg), admin- istered immediately after training, impaired rats' retention, 6 days later, of a one-way active avoidance task and a discriminated active avoidance task. In the discrimination task a lower dose (340 mg/kg) also impaired retention. Delayed posttraining injections did not affect retention in either task. The findings indicate that DDC can have similar effects on retention of tasks requiring quite different behavioral responses. Key words: Diethyldithiocarbamate - Avoidance behavior - Rats - Task differences - Retention - DDC Diethyldithiocarbamate (DDC) influences memory storage processes when the drug is administered shortly after animals are trained (cf. Gorelick et al., 1975, and references therein). Most studies report that DDC impaired retention, but recent studies using goldfish (Danscher and Fjerdingstad, 1975) and mice (Haycock et al., 1976) have obtained facilitating influences of posttraining DDC upon retention. Because DDC is known to impair the biosynthesis of norepinephrine (Lippman and Lloyd, 1969), these behavioral findings have been interpreted most frequently as indicating that norepinephrine may modulate neuronal processes involved in memory storage (Randt et al., 1971). How- ever, other interpretations have also been proposed (Danscher and Fjerdingstad, 1975; Haycock et al., 1976). Interestingly, posttraining DDC in rats has been shown to influence only retention of inhibitory avoidance learning (McGaugh et al., 1975). In order to examine the generality of the effects of DDC on retention in rats, the present study investigated post- * Presently at Department of Biology, University of San Diego, San Diego, California 92110, U.S.A. training DDC in a one-way active avoidance task and a discriminated active avoidance task. Two doses of DDC were investigated, one found to impair reten- tion of an inhibitory avoidance task and a lower dose ineffective in this task (McGaugh et al., 1975). MATERIALS AND METHODS Male Sprague-Dawley rats (50- 70 days old upon arrival, Simonsen Labs, Gilroy, CA) were used. The animals were individually housed and maintained on a 12/12 h light-dark cycle (7.00 a.m. on, 7.00 p.m. off) with food and water continuously available. Five days or longer after arrival, the animals were trained on one of two tasks described below. Drug treatments were given at one of several times after training, and retention tests were given 6 days after training. Training and testing were performed between 9.00 a.m. and 5.00 p.m. The one-way active avoidance task consisted of a trough-shaped alleyway (91 cm long, 15 cm deep, 6 and 20 cm wide at bottom and top, respectively) divided into two compartments (30 and 60 cm long) by an opaque plastic barrier (9 cm high). The floor and walls of the larger compartment were Iined with metal plates through which footshock (1 mA RMS) could be delivered. Training and testing (retraining 6 days later) each consisted of 8 trials (30 s inter- trial interval). For each trial the animal was placed into the larger darkened compartment. The footshock was activated 10 s later and remained on until the animal escaped over the barrier into the smaller Tensor-illuminated compartment. (Escape latencies were less than 5 s.) An avoidance was scored if the animal entered the smaller compartment before the onset of footshock. The discriminated active avoidance task consisted of a Y-maze (equilateral arms, 51 cm long, 13 cm wide, 15 cm deep) with grid floors through which a 0.7 mA (RMS) scrambled shock could be delivered to any arm. All animals were allowed 30 s of free explora- tion in the darkened maze 1 h prior to training. Training and testing (retraining 6 days later) each consisted of 6 trials. On each trial the animal was placed upon electrified grids in the start arm and allowed to escape into the safe arm (illuminated through a translucent plastic plate at the end of the anu). The start arm, center grids, and nonilluminated arm were constantly electrified during a trial. The position of the illuminated arm was varied according to a random sequence. After 5 s in the safe illuminated arm the animal was removed and replaced in the start arm. A correct response was scored if the animal entered the illuminated arm without first entering the nonilluminated arm.