Pharmacology Biochemistry & Behavior, Vol. 9, pp. 735-740. Printed in the U.S.A. Cycloheximide Produces Attentional Persistence and Slowed Learning in Chickens L.J. ROGERS Pharmacology Department, Monash University, Clayton, Victoria, 3168, Australia AND J. M. ANSON Department of Behavioural Biology, Australian National University, Canberra, Australia (Received 17 February 1978) ROGERS, L. J. AND J. M. ANSON. Cycloheximide produces attentional persistence and slowed learning in chickens. PHARMAC. BIOCHEM. BEHAV. 9(6) 735-740, 1978.--Cycloheximide has been used previously to demonstrate that long-term memory has a protein substrate. We have shown that it has two additional behavioural effects when it is administered to young chickens. A dose of 10/zg of cycloheximide in 5 p.l of normal saline vehicle given to each side of the forebrain on Day 2 of post-hatched life changes attention so that responding to a given stimulus type becomes more persistent. Behavioural testing occurred in the chickens' second week of life. They were given two colours of food, and runs of pecks at each colour were scored. Treated chicks showed less frequent switching from one colour to the other. A 20 /~g dose of cycloheximide in 25/~1 of saline also produced this state of attentional persistence, and additionally it made the chickens slower at learning a visual discrimination task, a visual habituation task and an auditory habituation task. The paper concludes that the effect on attention is separate from that on learning, and discusses the findings with reference to testosterone's known ability to produce attentional persistence and also with reference to previous research with cyc- loheximide and long-term memory. Cycloheximide Attentional persistence Visual discrimination learning Chickens Slowed learning Long-term memory Retrieval CYCLOHEXIMIDE, a drug which blocks ribosomal protein synthesis, has been used frequently in studies on memory formation, where it is claimed to block consolidation of long term memory [5, 6, 8, 13]. In addition to this property, cy- cloheximide has been found to produce a permanent reduc- tion in learning rate when it is administered to young chick- ens [12]. When administered intracranially to a chicken in the first week of life, it not only blocks the formation of long term memory of tasks performed about the time of treat- ment, but it also alters the brain in such a way that learning on a number of visual and auditory tasks is found to be permanently retarded. Our previous studies have almost always used a 20/~g dose of cycloheximide dissolved in 25/~1 of normal saline administered to each side of the forebrain [12,13]. We there- fore considered it important to measure the amount of learn- ing retardation produced by varying the amounts of cy- cloheximide administered in various volumes of saline, and from these studies an interesting new effect of cycloheximide on behaviour emerged. Cycloheximide was found to cause the chicken to persist in responding to a given stimulus type once it had begun responding to that stimulus type. This appeared to be re- markably similar to the persistence in responding, or atten- tional persistence, found previously in male chickens treated with testosterone [4,11]. It was therefore studied in visual search tests designed to measure attentional persistence by scoring runs of pecking on differently coloured food. By appropriate choice of dose followed by measuring both learn- ing rate on a visual discrimination task and attentional persis- tence, it was possible to separate learning effects from those of attentional persistence. LEARNING RATES METHOD Housing White leghorn-black australorp cross male chickens were obtained from a commercial hatchery on Day 1 of life. They were housed in groups of 4-6 birds until the evening of Day 3 when they were separated visually from each other. The cages (23x23 cm sq. and 29 cm high) were made of metal with a clear perspex front, through which the chickens could see the daily activity in the laboratory and become familiarized with the experimenter. Constant light and warmth were provided by a 25 W globe suspended above the cage. (For further details see [14]). Feeding Food and water were freely available and changed reg- Copyright © 1978 ANKHO International Inc.--0091-3057/78/120735-06501.10/0