Pharmacology Biochemistry and Behavior, Vol. 1, pp. 599-603. ANKHO International Inc., 1973. Printed in the U.S.A. Learning Deficits in Lead-Injected Rats 1 CHARLES T. SNOWDON Department of Psychology, University of Wisconsin, Madison, Wisconsin 53 706 (Received 6 June 1973) SNOWI)ON, C. T. Learning deficits in lead-injected rats. PHARMAC. BIOCHEM. BEHAV. 1(6)599-603, 1973. --Weanling and adult rats injected with one of three concentrations of lead acetate for 37 days failed to demonstrate any learning impairments as measured by a Hebb-Williams maze series relative to water injected controls. Rats at the highest dose level showed clear symptoms of lead poisoning. Pregnant females injected during pregnancy with an asymptomatic dose of lead acetate showed a 100% abortion rate, while 75% of water injected controls delivered litters. Rats whose mothers were injected with asymptomatic doses of lead acetate throughout nursing developed more slowly, weighed less, and demon- strated learning deficits relative to controls. The behavioral and physiological effects of lead may be greatest during the earliest developmental stages. Learning deficits Prenatal Postnatal TI4E USE of laboratory animals, such as the rat, as experi- mental models for the behavioral effects of lead poisoning has been limited by the failure to find evidence in animals of the intellectual impairment commonly found among young human victims of lead poisoning [6, 14]. The pre- vious experimental studies with rats have used either injec- tions of 1.5 mg/100 g body weight of tetraethyl lead for an eight day period in adult female rats [5] or 10 rag/100 g body weight of lead acetate for a three or four day period in weanling male rats [4]. Both experiments used a water escape maze as the means of evaluating learning deficits and both failed to find differences between lead injected and control animals, even though some of their animals display- ed symptoms of lead poisoning. The use of smaller doses of lead administered over a longer time course might better approximate the chronic lead poisoning of young humans and the water escape maze might not prove to be the most sensitive indicator of learn- ing deficits. Indeed, Davenport and Dorcey [81 have report- ed that in experiments evaluating the effects of thiouracil injections in rats, only the ltebb-Williams maze series out of nine behavioral measures of learning used detected learning impairments in the treated animals. In the work to be re- ported here the use of a prolonged series of small doses of lead injection and use of a Hebb-Williams maze series was expected to better elucidate learning deficits in lead inject- ed animals. In addition we thought it valuable to examine the effects of lead exposure at each of four developmental time periods: prenatally, during nursing, post weaning and adulthood. EXPERIMENT I: EFFECTS OF LEAD ACETATE INJECTIONS ON LEARNING IN WEANLING AND ADULT RATS Me th od Animals. The animals were 56 adult and 56 weanling rats obtained from the Sprague-Dawley Colony in Madison, Wisconsin. Apparatus. The apparatus used was a semi-automated version of the Hebb-Williams maze modified from the symmetrical maze designed by Davenport et al. [71. The maze consisted of a 76 cm sq. field enclosed by wooden walls 7.5 cm high. Start-goal alleys, which were 42.5 cm long, extended from the field at diagonally opposite ends. Wooden barriers (7.5 cm high and 1.9 cm thick) of varying lengths divided the field into symmetrical maze patterns. A bolt imbedded in one edge of the barrier was inserted through the expanded aluminum flooring and fastened to hold the barrier in place. All wooden surfaces were painted flat black. Lehigh Valley pellet feeders dispensed one 45 mg Noyes pellet per trial into a shallow aluminum dish at the far end of each start-goal alley. A galvanized steel plate electrically isolated from the floor of the alley was placed in front of each feeding dish. This was wired to a contact detection circuit [see 12]. When an animal made contact with this plate, pneumatic doors closed and an intertrial timer was started. At the end of the 10 sec ITI the doors were opened and a pellet dispensed to the opposite goal box. Observers trained in the scoring system of Davenport et al, 17] scored the animal's errors and recorded total errors and time to the Supported by Office of Education Grant PEG 5-71-0052 (508) and the University of Wisconsin Graduate School Research Council. 1 wish to thank J. D. Culbertson, S. R. Gilman, J. Kaufman, D. Knox, and J. Sanders who helped with the maze testing. 599