The action of locust neuromodulatory neurons is coupled to specific motor
patterns.
Burrows, M., and H. J. Pfluger.
Institut f[umlaut]ur Neurobiologie, Freie Universit[umlaut]at Berlin,
K[diaeresis]onigi, Luise Strasse
28-30, D-14195 Berlin, Germany.
APStracts 2:0022N, 1995.
SUMMARY AND CONCLUSIONS
Many muscles of the locust are supplied by dorsal unpaired median neurons (DUM
neurons) that release octopamine and alter the contractions caused by spikes
in motor neurons. To determine when these neuromodulatory neurons are normally
activated during behaviour, intracellular recordings were made simultaneously
from them and from identified motor neurons during the specific motor pattern
that underlies kicking. A kick consists of a rapid and powerful extension of
the tibia of one or both hind legs that is produced by a defined motor
pattern. Only three identified DUM neurons of the 20 in the metathoracic
ganglion, spike during a kick and they supply muscles involved in generating
the kick. Their spikes occur in a distinctive and repeatable pattern that is
closely linked to the pattern of spikes in the flexor and extensor tibiae
motor neurons. When the extensor and flexor muscles co-contract, these three
DUM neurons produce a burst of spikes at frequencies that can rise to 25Hz,
and with the number of spikes (3-15) related to the duration of this phase of
the motor pattern. The spikes stop when the flexor muscle is inhibited and
therefore before the tibia is extended rapidly. The other DUM neurons which
supply muscles that are not directly involved in kicking are either inhibited
or spike only sporadically. The activation of a specific subset of DUM
neurons during kicking may thus be timed to influence the action of the
muscles that participate in this movement, and appear to be controlled by the
same circuits that determine the actions of the participating motor neurons.
These modulatory neurons thus have specific individual actions in the control
of movement.
Received 28 November 1994; accepted in final form 8 March 1995.
APS Manuscript Number J740-4.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 3 April 1995.