Identification of Excitatory Interneurons Contributing to Generation of Locomotion in Lamprey: Structure, Pharmacology, and Function
Document Type
Article
Language
eng
Format of Original
11 p.
Publication Date
7-1989
Publisher
American Physiological Society
Source Publication
Journal of Neurophysiology
Source ISSN
0022-3077
Original Item ID
DOI: 10.1152/jn.1989.62.1.59
Abstract
1. In the in vitro preparation of the lamprey spinal cord, paired intracellular recordings of membrane potential were used to identify interneurons producing excitatory postsynaptic potentials (EPSPs) on myotomal motoneurons. 2. Seventy-nine interneurons (8.4% of all neuron-motoneuron pairs tested) elicited unitary EPSPs that followed one-for-one at short, constant latencies and were therefore considered monosynaptic according to conventional criteria. Evidence was obtained for selectivity and divergence of excitatory interneuron (EIN) outputs and for convergence of EIN input to motoneurons. 3. The neurotransmitter released by EINs may be an excitatory amino acid such as glutamate, because the EPSPs were depressed by antagonists of excitatory amino acids. 4. Intracellular dye injection revealed that EINs have small cell bodies (average 11 x 27 microns), transversely oriented dendrites, and thin (less than 3 microns) slowly conducting axons (0.7 m/s) that project caudally and ipsilaterally. One EIN exhibited a system of thin multi-branching axon collaterals with periodic swellings. Ultrastructurally, these swellings contained clear spherical vesicles, and they apposed postsynaptic membrane specializations. 5. During fictive locomotion, the membrane-potential oscillations of EINs were greater in amplitude than, but similar in shape and timing to, those of their postsynaptic motoneurons. EINs fired action potentials during fictive locomotion and contributed to the depolarization of motoneurons. 6. These interneurons are proposed to be a source of excitation to motoneurons and interneurons in the lamprey spinal cord, participating in motor activity including locomotion.
Recommended Citation
Buchanan, James T.; Grillner, Stan; Cullheim, Staffan; and Risling, Mårten, "Identification of Excitatory Interneurons Contributing to Generation of Locomotion in Lamprey: Structure, Pharmacology, and Function" (1989). Biological Sciences Faculty Research and Publications. 166.
https://epublications.marquette.edu/bio_fac/166
Comments
Journal of Neurophysiology, Vol. 62, No. 1 (July 1989): 59-69. DOI.
James Buchanan was affiliated with the Karolinska Institute at the time of publication.