Journal of Neurophysiology, Vol 70, Issue 1 263-274, Copyright © 1993 by APS

ARTICLES

Organization of inhibition in the rat olfactory bulb external plexiform layer

P. I. Ezeh, D. P. Wellis and J. W. Scott
Department of Anatomy and Cell Biology, Emory University School of Medicine, Atlanta, Georgia 30322.

1. Intracellular recordings were made from the output neurons (mitral and tufted cells) of the rat olfactory bulb during electrical orthodromic stimulation of the olfactory nerve layer (ONL) and antidromic stimulation of the lateral olfactory tract and posterior piriform cortex (pPC) to test for physiological differences among the neuron types. Many of these neurons were identified by intracellular injections of biocytin, and others were identified by their pattern of antidromic activation. 2. Both marked and unmarked mitral cells showed large inhibitory postsynaptic potentials (IPSPs) in response to antidromic stimulation of the pPC, whereas tufted cells exhibited small IPSPs in response to pPC stimulation. Tufted cells, however, showed large IPSPs in response to ONL stimulation. In many cases, these tufted cell responses to ONL stimulation were larger than the mitral cell responses. The marked superficial tufted cells, those with basal dendrites in the superficial sublayer of the external plexiform layer (EPL), had the smallest IPSPs in response to pPC stimulation. These data support anatomic observations suggesting that the granule cell populations responsible for the IPSPs may be different for mitral and for superficial tufted cells. 3. The different types of output cells also showed differences in their responses to orthodromic stimulation. Type I mitral cells, which have basal dendrites confined to the deep sublayer of the EPL, were significantly less excitable by ONL stimulation than were the type II mitral cells, which have basal dendrites distributed within the intermediate sublayer of the EPL. Half of the type I mitral cells could not be excited at all by ONL stimulation. Superficial tufted cells showed even greater orthodromic excitability than type II mitral cells, usually responding to ONL stimulation with two or more spikes. 4. The ionic basis of the IPSPs in the superficial tufted cells appeared similar to those described for mitral cells. These IPSPs could be reversed by chloride injection and were associated with increased membrane conductance. 5. For both mitral and tufted cells, the number of ONL electrodes evoking IPSPs was greater than the number evoking spikes. These data suggest a kind of center-surround organization of inputs to these cells from the ONL, although this does not yet imply that the sensory receptive field of these output cells has a center-surround organization. 6. In conclusion, the properties of rat olfactory bulb output cells correlate with the sublayers of the EPL in which their basal dendrites lie.(ABSTRACT TRUNCATED AT 400 WORDS)

This article has been cited by other articles:

				E. R. Griff, M. Mafhouz, A. Perrut, and M. A. Chaput Comparison of Identified Mitral and Tufted Cells in Freely Breathing Rats: I. Conduction Velocity and Spontaneous Activity Chem Senses, July 16, 2008; (2008) bjn041v1. [Abstract] [Full Text] [PDF]

				K. A. Hamilton, S. Parrish-Aungst, F. L. Margolis, F. Erdelyi, G. Szabo, and A. C. Puche Sensory Deafferentation Transsynaptically Alters Neuronal GluR1 Expression in the External Plexiform Layer of the Adult Mouse Main Olfactory Bulb Chem Senses, February 1, 2008; 33(2): 201 - 210. [Abstract] [Full Text] [PDF]

				S. Nagayama, Y. K. Takahashi, Y. Yoshihara, and K. Mori Mitral and Tufted Cells Differ in the Decoding Manner of Odor Maps in the Rat Olfactory Bulb J Neurophysiol, June 1, 2004; 91(6): 2532 - 2540. [Abstract] [Full Text] [PDF]

				A. P. Davison, J. Feng, and D. Brown Dendrodendritic Inhibition and Simulated Odor Responses in a Detailed Olfactory Bulb Network Model J Neurophysiol, September 1, 2003; 90(3): 1921 - 1935. [Abstract] [Full Text] [PDF]

				B. Halabisky and B. W. Strowbridge {gamma}-Frequency Excitatory Input to Granule Cells Facilitates Dendrodendritic Inhibition in the Rat Olfactory Bulb J Neurophysiol, August 1, 2003; 90(2): 644 - 654. [Abstract] [Full Text] [PDF]

				A. R. McQuiston and L. C. Katz Electrophysiology of Interneurons in the Glomerular Layer of the Rat Olfactory Bulb J Neurophysiol, October 1, 2001; 86(4): 1899 - 1907. [Abstract] [Full Text] [PDF]

				J. M. Christie, N. E. Schoppa, and G. L. Westbrook Tufted Cell Dendrodendritic Inhibition in the Olfactory Bulb Is Dependent on NMDA Receptor Activity J Neurophysiol, January 1, 2001; 85(1): 169 - 173. [Abstract] [Full Text] [PDF]