Electrophysiological and Pharmacological Characterization of the Direct
Perforant Path Input to the Hippocampal Area CA3.
Julia Berzhanskaya, Nathaniel N. Urban, and German Barrionuevo.
Deparment of Neuroscience and Center for the Neural Basis of Cognition,
University of Pittsburgh, Pittsburgh, PA 15260.
APStracts 4:355N, 1997.
Monosynaptic perforant path responses evoked by subiculum stimulation were
recorded from CA3 pyramidal cells of rat hippocampal slices. These
monosynaptic responses were isolated by using low intensities of stimulation
and by placing a cut through the mossy fibers. Perforant path evoked responses
consisted of both excitatory and inhibitory components. EPSCs were mediated by
both AMPA receptors (AMPAR) and NMDA receptors (NMDAR). IPSCs consisted of
GABAA- and GABAB -receptor mediated components. At membrane potentials more
positive than -60 mV and at physiological [Ca2+]/[Mg2+] ratios, more than 30%
of perforant path evoked EPSC was mediated by NMDARs. This value varied as a
function of the membrane voltage and external [Mg2+]. Two types of responses
were observed following low intensity stimulation of the perforant path. The
first type of response showed paired-pulse facilitation and was reduced by
AP4. The second type of response showed paired-pulse depression and was
reduced by baclofen. Electrophysiological and pharmacological characteristics
of these two types of responses are similar to the properties of lateral and
medial perforant path evoked EPSPs in the dentate gyrus.
Received 17 July 1997; accepted in final form 3 December 1997.
APS Manuscript Number J595-7.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1997 The American Physiological Society.
Published in APStracts on 12 December 1997