Individual differences in emergence neophobia predict magnitiude of perforant-path long-term potentiation (LTP) and plasma corticosterone levels in rats

Abstract

Emergence neophobia was assessed in an emergence apparatus that provided a choice between novel and familiar alternatives. Two weeks following emergence testing the threshold to induce perforant path long-term potentiation (LTP) and the magnitude of perforant path LTP in the dentate gyrus were assessed under pentobarbital anesthesia. Two measures of emergence behavior, the total duration of time spent in the alley during the one hour test (ED) and the emergence duration per entry into the novel compartment (D/E), were significantly correlated (ED: r = -.57, p < .05; D/E: r = -.74, p < .001) with LTP of the extracellular population excitatory postsynaptic potential (EPSP), but not the population spike (PS). Neophobic animals that spent relatively little time in the novel alley during the one hour test had both a lower threshold to induce LTP and exhibited greater asymptotic EPSP LTP than neophilic animals that readily entered and explored the novel alley. In a second experiment, plasma corticosterone levels in animals tested in the emergence task were also correlated (r = .65, p < .02) with emergence duration, and were generally lower in neophobic animals. Together these data suggest that neotic behavior and LTP share a common mechanism, possibly one mediated by an interaction of glucocorticoid hormones and habituation.