Classical conditioning of the rabbit eyelid response increases glutamate receptor binding in hippocampal synaptic membranes.
Hippocampal pyramidal neurons exhibit a rapid within-trial increase in firing frequency during classical conditioning of the rabbit eyelid response. It has been proposed that the cellular mechanisms responsible for hippocampal long-term potentiation (LTP) may also mediate this learning-dependent increase in neuronal activity. The induction of LTP in rat hippocampal slices results in an increase in the number of [3H]glutamate-binding sites in the potentiated region. The present study investigates the kinetics of [3H]glutamate binding to hippocampal synaptic membranes after eyelid conditioning in the rabbit. We report that the regional distribution of [3H]glutamate binding across the layers of rabbit hippocampus is compatible with a dendritic localization. The pharmacological and ionic properties of the binding suggest that it is associated with an excitatory amino acid receptor. After eyelid conditioning, the maximal number of hippocampal [3H]glutamate-binding sites is increased in animals receiving paired presentations of the tone conditioned stimulus and corneal air-puff unconditioned stimulus relative to that found in naive or unpaired control animals. These results strengthen the hypothesis that an LTP-like mechanism underlies the increase in hippocampal firing frequency during rabbit eyelid conditioning.
D000818:Animals; D002118:Calcium / Q000494:pharmacology; D003214:Conditioning, Classical; D003215:Conditioning, Eyelid; D005971:Glutamates / Q000378:metabolism*; D018698:Glutamic Acid; D006624:Hippocampus / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D011712:Pyramidal Tracts / Q000378:metabolism; D011817:Rabbits; D011956:Receptors, Cell Surface / Q000378:metabolism*; D017470:Receptors, Glutamate; D013570:Synaptic Membranes / Q000378:metabolism*
D005971:Glutamates; D011956:Receptors, Cell Surface; D017470:Receptors, Glutamate; D018698:Glutamic Acid; D002118:Calcium