CONFLICT BEHAVIOR IN MAUDSLEY REACTIVE AND NONREACTIVE RATS - EFFECTSOF NORADRENERGIC NEURONAL DESTRUCTION

The present studies were designed to examine the effects of treatment with the noradrenergic neurotoxin N-(2-chloroethyl)-n-ethyl-2-bromoben zylamine HCl (DSP4; 65 mg/kg, IP) on conflict behavior in the Maudsley reactive (MR) and nonreactive (MNRA) rat strains. In daily 10-min ses sions, water-restricted rats were trained to drink water from a tube t hat was occasionally electrified; electrification was signaled by the presence of a tone (7-s duration; ISI = 30 s). Consistent with previou s reports, the number of shocks accepted by rats of the MR and MNRA st rains did not differ initially, but MNRA rats exhibited a dramatic inc rease in punished responding relative to their MR counterparts over th e course of several weeks of conflict testing. This MR vs. MNRA strain difference in punished responding did not exhibit extinction followin g discontinuation of CSD conflict behavior testing for a period of 6 w eeks. Whether it was administered after conflict training or before, D SP4 treatment did not reduce the MR vs. MNRA strain difference in conf lict behavior; rather, DSP4 treatment tended to increase the magnitude of the MR vs. MNRA difference in conflict behavior. The effects of DS P4 on norepinephrine (NE) and 5-hydroxytrypamine (5-HT) concentrations in the pons medulla region were determined in one group of conflict-e xperienced MR and MNRA rats (35 weeks after administration) and in a s econd group of naive MR and MNRA rats (3 weeks after administration). There were no MR vs. MNRA strain differences in NE or 5-HT concentrati ons in vehicle-treated rats. DSP4 treatment significantly reduced NE, but not 5-HT, concentrations when compared to control values; rats tha t were sacrificed 3 weeks following DSP4 administration exhibited a gr eater NE depletion than did rats sacrificed 35 weeks after DSP4 admini stration. Finally, there were no significant correlations between pons medulla region NE concentrations and conflict behavior in either stra in alone or when the data from the two strains were combined. The pres ent results are not consistent with the hypothesis that the MR vs. MNR A strain difference in conflict behavior is the result of strain diffe rences in brain NE function.