Volume 16, Number 16,
Issue of August 15, 1996
pp. 5266-5279
Copyright ©1996 Society for Neuroscience
An Identified Interneuron Contributes to Aspects of Six Different
Behaviors in Aplysia
Received Feb. 16, 1996; revised June 12, 1996; accepted June 14, 1996.
Yuanpei Xin1,
Klaudiusz
R. Weiss2, and
Irving Kupfermann1
1 Center for Neurobiology and Behavior, College of
Physicians and Surgeons, Columbia University, New York, New York,
10032, and 2 Department of Physiology and Biophysics, Mount
Sinai Medical Center, New York, New York 10029
Previous results have indicated that the bilateral cerebral
interneuron CC5 mediates the pedal artery shortening that is a
component of defensive withdrawal responses involving the head. Current
studies suggest that CC5 contributes to aspects of at least six
different behaviors: locomotion, head turning, defensive head
withdrawal, local tentacular withdrawal, rhythmic feeding, and head
lifting. In addition to receiving input from mechanoreceptors in the
head, CC5 receives synaptic input during fictive locomotor and feeding
programs. Firing of CC5 produces widespread monosynaptic or
polysynaptic actions in all ganglia in the animal. CC5 excites
presumptive motor neurons for the neck, and its activity can contract
neck muscles. The pedal artery shortener motor neuron (PAS), a key
excitatory follower cell of CC5, fires during ipsilateral head turning,
head withdrawal, tentacle withdrawal, feeding, and locomotion. For all
behaviors, except locomotion and biting, responses of PAS were
eliminated by cutting the ipsilateral-pleural connective, which
interrupts the only direct connection of CC5 to the ipsilateral PAS.
The data suggest that CC5 is a multifunctional interneuron that plays
different roles during different behaviors. The neuron appears to be
involved in producing coordinated movements of the head, involving both
somatic and visceral muscles. For some behaviors, or for certain
aspects of behaviors, CC5 appears to act as an individual command-like
neuron; for other behaviors, CC5 appears to act more as an element of a
distributed circuit and is neither necessary nor sufficient for any
aspects of the behavior.
Key words:
command;
withdrawal reflex;
Aplysia;
mechanosensory;
feeding;
head turning;
locomotion
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