Noradrenergic and locus coeruleus modulation of the perforant path-evoked potential in rat dentate gyrus supports a role for the locus coeruleus in attentional and memorial processes.
The perforant path-dentate gyrus synapse has provided a model system for functional neural plasticity in adult mammalian brain. NMDA-dependent long-term changes in neural connectivity occur at this synapse in response to high-frequency input. Norepinephrine (NE) applied exogenously or released endogenously can initiate both a short- and a long-term potentiation (LTP) of the dentate gyrus response to perforant path input. Triggering of the potentiated response depends on beta-receptor activation and does not require a high-frequency stimulus. An increase in locus coeruleus (LC) activity can initiate both short and LTP of the perforant path response, although a reduction in LC activity does not alter baseline perforant path responses. This chapter considers differences between NE modulation in vitro and in vivo, differences and similarities between NE-LTP and frequency-induced LTP, and the surprising specificity of NE effects at the perforant path synapse. Studies of NE in the dentate gyrus support a role for the LC in promoting both short- and long-term enhancement of responses to complex sensory inputs and are consistent with a role for the LC in memorial as well as attentional processes.
Department of Psychology, Memorial University of Newfoundland, St. John's, Canada.
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D000818:Animals; D001245:Association Learning / Q000502:physiology*; D001288:Attention / Q000502:physiology*; D005071:Evoked Potentials / Q000187:drug effects; D018691:Excitatory Amino Acid Antagonists; D005971:Glutamates / Q000494:pharmacology; D018698:Glutamic Acid; D006624:Hippocampus / Q000502:physiology*; D008125:Locus Coeruleus / Q000187:drug effects / Q000502:physiology*; D008568:Memory / Q000502:physiology*; D008959:Models, Neurological; D009473:Neuronal Plasticity / Q000502:physiology; D009638:Norepinephrine / Q000502:physiology*; D011433:Propranolol / Q000494:pharmacology; D051381:Rats; D016194:Receptors, N-Methyl-D-Aspartate / Q000502:physiology; D013569:Synapses / Q000502:physiology
D018691:Excitatory Amino Acid Antagonists; D005971:Glutamates; D016194:Receptors, N-Methyl-D-Aspartate; D018698:Glutamic Acid; D011433:Propranolol; D009638:Norepinephrine