title: Presynaptic inhibition of Schaffer collateral synapses by stimulation of hippocampal cholinergic afferent fibres.
abstract: It has been known for decades that muscarinic agonists presynaptically inhibit Schaffer collateral synapses contacting hippocampal CA1 pyramidal neurons. However, a demonstration of the inhibition of Schaffer collateral synapses induced by acetylcholine released by cholinergic hippocampal afferents is lacking. We present original results showing that electrical stimulation at the stratum oriens/alveus with brief stimulus trains inhibited excitatory postsynaptic currents evoked by stimulation of Schaffer collaterals in CA1 pyramidal neurons of rat hippocampal slices. The increased paired-pulse facilitation and the changes in the variance of excitatory postsynaptic current amplitude that paralleled the inhibition suggest that it was mediated presynaptically. The effects of oriens/alveus stimulation were inhibited by atropine, and blocking nicotinic receptors with methyllycaconitine was ineffective, suggesting that the inhibition was mediated via the activation of presynaptic muscarinic receptors. The results provide a novel demonstration of the presynaptic inhibition of glutamatergic neurotransmission by cholinergic fibres in the hippocampus, implying that afferent cholinergic fibres regulate the strength of excitatory synaptic transmission.
authors.affiliation: Instituto Cajal, CSIC, Avenida Doctor Arce 37, 28002-Madrid, Spain.
authors.forename: David
authors.initials: D
authors.lastname: Fernández de Sevilla
authors.forename: Washington
authors.initials: W
authors.lastname: Buño
mesh_terms: D000818:Animals; D001285:Atropine / Q000494:pharmacology; D002799:Cholinergic Fibers / Q000378:metabolism / Q000502:physiology*; D004558:Electric Stimulation; D019706:Excitatory Postsynaptic Potentials / Q000502:physiology; D018698:Glutamic Acid / Q000378:metabolism; D006624:Hippocampus / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D008564:Membrane Potentials / Q000502:physiology; D018727:Muscarinic Antagonists / Q000494:pharmacology; D009475:Neurons, Afferent / Q000378:metabolism / Q000502:physiology; D018408:Patch-Clamp Techniques; D051381:Rats; D017208:Rats, Wistar; D017661:Receptors, Presynaptic / Q000378:metabolism / Q000502:physiology*; D013569:Synapses / Q000378:metabolism / Q000502:physiology*
chemical_list: D018727:Muscarinic Antagonists; D017661:Receptors, Presynaptic; D018698:Glutamic Acid; D001285:Atropine