Original contributionMembrane properties of identified lateral and medial perforant pathway projection neurons
Section snippets
Retrograde labeling and cell identification
All procedures were carried out in strict adherence to international guidelines on the ethical use of animals and all efforts were made to minimize the number of animals used and their suffering. A combination of fluorescence labeling and whole-cell recording in brain slices was employed. Briefly, Sprague–Dawley rats (12 days old) were placed in a stereotaxic frame under barbiturate anesthesia. Approximately 0.5–1.0 μl of a 5% solution of 3,3′-dioctadecyloxacarbocyanine perchlorate (DiO;
Results
Injection of retrograde tracers (DiO or fluorescent polystyrene microspheres) into the dorsal hippocampus reliably labeled neurons in the superficial layers of the medial and lateral entorhinal cortices Dolorfo and Amaral 1998, Steward and Scoville 1976. MPP projection neurons were identified by fluorescence microscopy in layer II at the caudal pole of slices prepared in the horizontal plane. LPP projection neurons were identified in layer II, ventral to the rhinal sulcus, in rostral slices
Discussion
We have compared the membrane properties of layer II MPP and LPP projection neurons identified by retrograde tracing. The major differences between these neurons are: 1) LPP projection neurons have a higher input resistance, 2) MPP projection neurons have much more pronounced anomalous rectification, presumably due to their larger Ih currents, and 3) MPP projection neurons have large DAPs, fire action potential doublets, and can generate slow subthreshold depolarizing potentials, which
Acknowledgements
We thank John Dempster, Strathclyde University, for supplying data acquisition software (WinWCP). This work was supported by a grant from the NIH (NS36455) and a Department of Veterans Affairs Merit Review.
References (27)
- et al.
Persistent sodium channel activity mediates subthreshold membrane potential oscillations and low-threshold spikes in rat entorhinal cortex layer V neurons
Neuroscience
(2001) - et al.
Calcium currents in acutely isolated stellate and pyramidal neurons of rat entorhinal cortex
Brain Res
(1999) - et al.
Lesions of the medial or lateral perforant path have different effects on hippocampal contributions to place learning and on fear conditioning to context
Behav Brain Res
(1999) - et al.
The axonal projection patterns of the mitral and tufted cells of the olfactory bulb in the rat
Brain Res
(1977) Evidence for two physiologically distinct perforant pathways to the fascia dentata
Brain Res
(1980)- et al.
Developmental changes of inward rectifier currents in neurons of the rat entorhinal cortex
Neurosci Lett
(1997) - et al.
Neurons of origin of the perforant path
Exp Neurol
(1981) - et al.
Differential electroresponsiveness of stellate and pyramidal-like cells of medial entorhinal cortex layer II
J Neurophysiol
(1993) - et al.
Subthreshold Na+-dependent theta-like rhythmicity in stellate cells of entorhinal cortex layer II
Nature
(1989) - et al.
Ionic basis of spike after-depolarization and burst generation in adult rat hippocampal CA1 pyramidal cells
J Physiol
(1996)