Biomaterial Database

Control of pedal and parapodial movements in Aplysia. II. Cerebral ganglion neurons. 1978

B Jahan-Parwar, and S M Fredman

1. Intracellular stimulation of individual neurons in the two symmetrical A neuron clusters of the cerebral ganglion evoked contractions of both the foot and parapodia. Electrical stimulation of pedal and parapodial nerves caused antidromic action potentials in A neurons. Units recorded in the nerves followed the driven somatic spike 1:1. This suggests that the A neurons are presumptive pedal and parapodial motor neurons.2. Individual A neurons evoked both bilteral and unilateral contractions of the parapodia or split foot. Contractions in the parapodia were independent of those in the foot. An individual A neuron caused contractions in either the foot or the parapodia, but not both. Sequential transection of parapodial nerves had only a slight effect until a key nerve was cut. The contractions produced by a single A neuron on one side were then abolished. These data suggest that the motor fields of the A neurons are well defined within the foot or the parapodia. 3. Parapodial contractions produced by individual A neurons are not dependent on the excitation of follower motor neurons. Blocking synaptic transmission by the addition of CoCl2 did not eliminate the contractions produced by driving individual A neurons. This is consistent with the A neurons being motor neurons. 4. Intracellular stimulation of individual neurons in the symmetrical B neuron clusters of the cerebral ganglion also evoked pedal and parapodial contractions. Electrical stimulation of the pedal and parapodial nerves elicited antidromic spikes in these neurons. Individual B neurons caused contractions in both the foot and parapodia. This suggests that the B neurons are motor neurons with very large motor fields. 5. Filling the pedal and parapodial nerves with cobalt primarily filled the cell bodies of neurons located in the pedal and pleural ganglia. The somata of A and B neurons were also occasionally filled. This is consistent with the electrophisiological results. 6. Other neurons also evoked parapodial contractions. Intracellular stimulation of neurons in the pedal and pleural ganglia caused parapodial contractions in intact animals. Some of these neurons were excited by stretching the parapodia or touching the tentacles. 7. The B neurons are strongly excited by tactile stimulation of the tentacles. Since they can cause pedal and parapodial contractions they may mediate reflex contractions elicited by tentacular stimulation. Stretching the parapodia only occasionally caused the A neurons to fire. This makes it unlikely that they make a major contribution to pedal and parapodial proprioceptive reflexes. These reflexes are probably controlled by neurons in the pedal and pleural ganglia.

UI	MeSH Term	Description	Entries
D009046	Motor Neurons	Neurons which activate MUSCLE CELLS.	Neurons, Motor,Alpha Motorneurons,Motoneurons,Motor Neurons, Alpha,Neurons, Alpha Motor,Alpha Motor Neuron,Alpha Motor Neurons,Alpha Motorneuron,Motoneuron,Motor Neuron,Motor Neuron, Alpha,Motorneuron, Alpha,Motorneurons, Alpha,Neuron, Alpha Motor,Neuron, Motor
D009068	Movement	The act, process, or result of passing from one place or position to another. It differs from LOCOMOTION in that locomotion is restricted to the passing of the whole body from one place to another, while movement encompasses both locomotion but also a change of the position of the whole body or any of its parts. Movement may be used with reference to humans, vertebrate and invertebrate animals, and microorganisms. Differentiate also from MOTOR ACTIVITY, movement associated with behavior.	Movements
D009435	Synaptic Transmission	The communication from a NEURON to a target (neuron, muscle, or secretory cell) across a SYNAPSE. In chemical synaptic transmission, the presynaptic neuron releases a NEUROTRANSMITTER that diffuses across the synaptic cleft and binds to specific synaptic receptors, activating them. The activated receptors modulate specific ion channels and/or second-messenger systems in the postsynaptic cell. In electrical synaptic transmission, electrical signals are communicated as an ionic current flow across ELECTRICAL SYNAPSES.	Neural Transmission,Neurotransmission,Transmission, Neural,Transmission, Synaptic
D009474	Neurons	The basic cellular units of nervous tissue. Each neuron consists of a body, an axon, and dendrites. Their purpose is to receive, conduct, and transmit impulses in the NERVOUS SYSTEM.	Nerve Cells,Cell, Nerve,Cells, Nerve,Nerve Cell,Neuron
D011930	Reaction Time	The time from the onset of a stimulus until a response is observed.	Response Latency,Response Speed,Response Time,Latency, Response,Reaction Times,Response Latencies,Response Times,Speed, Response,Speeds, Response
D012018	Reflex	An involuntary movement or exercise of function in a part, excited in response to a stimulus applied to the periphery and transmitted to the brain or spinal cord.
D003035	Cobalt	A trace element that is a component of vitamin B12. It has the atomic symbol Co, atomic number 27, and atomic weight 58.93. It is used in nuclear weapons, alloys, and pigments. Deficiency in animals leads to anemia; its excess in humans can lead to erythrocytosis.	Cobalt-59,Cobalt 59
D004558	Electric Stimulation	Use of electric potential or currents to elicit biological responses.	Stimulation, Electric,Electrical Stimulation,Electric Stimulations,Electrical Stimulations,Stimulation, Electrical,Stimulations, Electric,Stimulations, Electrical
D005724	Ganglia	Clusters of multipolar neurons surrounded by a capsule of loosely organized CONNECTIVE TISSUE located outside the CENTRAL NERVOUS SYSTEM.
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia