QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

HOME  |   SEARCH  |   ARCHIVE  |   SUBSCRIBE  |   CONTACT  |   HELP

This Article Full Text (PDF) Submit an eLetter Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Sherff, C. M. Articles by Mulloney, B. Search for Related Content PubMed PubMed Citation Articles by Sherff, C. M. Articles by Mulloney, B.

 Previous Article  |  Next Article 

Journal of Neuroscience, Vol 16, 2839-2859, Copyright © 1996 by Society for Neuroscience

ARTICLE

Tests of the motor neuron model of the local pattern-generating circuits in the swimmeret system

CM Sherff and B Mulloney
Division of Biological Sciences, University of California, Davis, 95616- 8755, USA.

The motor pattern that drives each crayfish swimmeret consists of alternating bursts of impulses in power-stroke (PS) and return-stroke (RS) motor neurons. A model of the neural circuit that generates this pattern focused on connections between motor neurons themselves (Heitler, 1978, 1981). The model predicts that synergist motor neurons are electrically coupled, whereas antagonists make mostly inhibitory synapses. We tested this model by observing the responses of motor neurons to pressure ejection of GABA and glutamate, transmitters that crayfish motor neurons release at neuromuscular junctions, and by measuring the strengths and delays of synapses between pairs of motor neurons. Both GABA and glutamate inhibited motor neurons. This inhibition persisted when synaptic transmitter release was blocked by high Mg2+. The effects of GABA were mimicked by muscimol, but not by baclofen or the GABAc receptor agonist cis-4-aminocrotonic acid, and they were not blocked by bicuculline. The effects of glutamate were mimicked by ibotenic acid. Picrotoxin partially blocked glutamate's inhibition of the motor pattern, but did not affect GABA responses. Most (87%) pairs of synergist motor neurons tested made weak, noninverting connections. Approximately half of these had synaptic delays of <2 msec, consistent with direct electrical or chemical synapses. Individual motor neurons were dye-coupled to between one and three other motor neurons, and to interneurons. Less than half (44%) of the pairs of antagonist motor neurons tested made synaptic connections. These connections were weak, had long latencies (>4 msec), and therefore were probably polysynaptic. We conclude that direct synapses between swimmeret motor neurons cannot account for alternation of PS and RS bursts.

This article has been cited by other articles:

				B. Mulloney and W. M. Hall Local and Intersegmental Interactions of Coordinating Neurons and Local Circuits in the Swimmeret System J Neurophysiol, July 1, 2007; 98(1): 405 - 413. [Abstract] [Full Text] [PDF]

				B. Mulloney, P. I. Harness, and W. M. Hall Bursts of Information: Coordinating Interneurons Encode Multiple Parameters of a Periodic Motor Pattern J Neurophysiol, February 1, 2006; 95(2): 850 - 861. [Abstract] [Full Text] [PDF]

				B. Mulloney During Fictive Locomotion, Graded Synaptic Currents Drive Bursts of Impulses in Swimmeret Motor Neurons J. Neurosci., July 2, 2003; 23(13): 5953 - 5962. [Abstract] [Full Text] [PDF]

				S. R. Jones, B. Mulloney, T. J. Kaper, and N. Kopell Coordination of Cellular Pattern-Generating Circuits that Control Limb Movements: The Sources of Stable Differences in Intersegmental Phases J. Neurosci., April 15, 2003; 23(8): 3457 - 3468. [Abstract] [Full Text] [PDF]

				N. Tschuluun, W. M. Hall, and B. Mulloney Limb Movements during Locomotion: Tests of a Model of an Intersegmental Coordinating Circuit J. Neurosci., October 1, 2001; 21(19): 7859 - 7869. [Abstract] [Full Text] [PDF]

				D. M. Blitz and M. P. Nusbaum Distinct Functions for Cotransmitters Mediating Motor Pattern Selection J. Neurosci., August 15, 1999; 19(16): 6774 - 6783. [Abstract] [Full Text] [PDF]

				H. Namba and B. Mulloney Coordination of Limb Movements: Three Types of Intersegmental Interneurons in the Swimmeret System and Their Responses to Changes in Excitation J Neurophysiol, May 1, 1999; 81(5): 2437 - 2450. [Abstract] [Full Text] [PDF]

				F. K. Skinner and B. Mulloney Intersegmental Coordination of Limb Movements during Locomotion: Mathematical Models Predict Circuits That Drive Swimmeret Beating J. Neurosci., May 15, 1998; 18(10): 3831 - 3842. [Abstract] [Full Text] [PDF]

				B. Mulloney, H. Namba, H.-J. Agricola, and W. M. Hall Modulation of Force during Locomotion: Differential Action of Crustacean Cardioactive Peptide on Power-Stroke and Return- Stroke Motor Neurons J. Neurosci., September 15, 1997; 17(18): 6872 - 6883. [Abstract] [Full Text] [PDF]

				C. M. Sherff and B. Mulloney Passive Properties of Swimmeret Motor Neurons J Neurophysiol, July 1, 1997; 78(1): 92 - 102. [Abstract] [Full Text] [PDF]

				H. Miyata, T. Nagayama, and M. Takahata Two Types of Identified Ascending Interneurons With Distinct GABA Receptors in the Crayfish Terminal Abdominal Ganglion J Neurophysiol, March 1, 1997; 77(3): 1213 - 1223. [Abstract] [Full Text] [PDF]

				B. Mulloney A Test of the Excitability-Gradient Hypothesis in the Swimmeret System of Crayfish J. Neurosci., March 1, 1997; 17(5): 1860 - 1868. [Abstract] [Full Text] [PDF]

Home  |   Search  |   Archive  |   Subscribe  |   Contact  |   Help