Sex differences in hippocampal long-term potentiation (LTP) and Pavlovian fear conditioning in rats: positive correlation between LTP and contextual learning.
Three experiments investigated sex differences in hippocampal long-term potentiation (LTP) and Pavlovian fear conditioning in rats. Experiment 1 revealed a robust sex difference in the magnitude of LTP induced at perforant path synapses in the dentate gyrus of pentobarbital-anesthetized rats. This sex difference in LTP was evident in rats of 35 and 60 days of age and was not the result of pre-LTP sex differences in perforant path synaptic transmission; 20-day-old rats did not show LTP. An analysis of field potentials evoked during LTP induction revealed a sex difference in the magnitude of N-methyl-D-aspartate (NMDA) receptor activation that was highly correlated with the magnitude of LTP. Experiment 2 showed that males condition more fear, measured as freezing, to the contextual conditional stimuli (CSs) of a conditioning chamber compared to their female counterparts. This sex difference in conditional freezing was apparent with both low and high unconditional stimulus (US, footshock) intensities. Experiment 3 revealed that the enhanced fear conditioning in males was specific to contextual CSs, and consisted of a more rapid rate of conditioning. Together, these experiments reveal a positive correlation between the magnitude of hippocampal LTP and a form of learning that depends on the hippocampus. Furthermore, they suggest a neural basis for sex differences in hippocampus-dependent learning tasks.
Department of Psychology, University of California, Los Angeles 90024-1563.
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Maren
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De Oca
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Fanselow
D000161:Acoustic Stimulation; D000704:Analysis of Variance; D000818:Animals; D003214:Conditioning, Classical; D004558:Electric Stimulation; D005071:Evoked Potentials; D005239:Fear; D005260:Female; D006624:Hippocampus / Q000502:physiology*; D007858:Learning; D017774:Long-Term Potentiation; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D016194:Receptors, N-Methyl-D-Aspartate / Q000502:physiology; D012727:Sex Characteristics; D013997:Time Factors
D016194:Receptors, N-Methyl-D-Aspartate