The effect of lead on increased aggressiveness and emotionality in the rat.

Abstract

Environmental pollution has become a focused concern of researchers in the recent past. Among the more common contaminants is lead, which has been implicated in emotional disorders (Marlowe, 1985) and hyperactivity (Rimland & Larson, 1983) in children. In addition, lead may play a role in increasing aggressive tendencies in both children and adults (Hanninen, 1982). In order to clarify some of the inconsistencies in the research literature, the present project was undertaken. Rats were chronically exposed to lead acetate (PB) via their drinking water for 60 days, or were given regular tap water (N). Following exposure, the sUbjects were trained in a straight runway and given either continuous (CRF) or parital (PRF) reinforcement. Thus, four groups resulted: PBPRF, PBCRF, NPRF and NCRF. Relying on classic frustration theory (Amsel, 1958), and assuming that lead does increase aggressiveness and emotionality, the prediction would be that those exposed to lead and given partial reinforcement (Group PBPRF) would persist longer during Extinction when compared to those subjects given water and receiving partial reinforcement (Group NPRF) . Conversely, those animals exposed to lead and receiving continuous reinforcement (Group PBCRF) would be expected to extinguish most rapidly because of the increased frustration experienced for the first time at the outset of Extinction, when compared to their water counterparts (Group NCRF). Results indicate that lead does lead to an increase in emotionality in the rat. Implications of this finding, along with future avenues for research, are discussed.