Document Detail

Central circuitry in the jellyfish Aglantha digitale. III. The rootlet and pacemaker systems.
MedLine Citation:
PMID:  10821737     Owner:  NLM     Status:  MEDLINE    
Tactile stimulation of the subumbrella of Aglantha digitale was found to evoke an escape swimming response similar to that evoked by stimulation of the outer surfaces of the margin but that does not involve the ring giant axon. Evidence is presented that conduction around the margin takes place via an interconnected system of rootlet interneurones. Confocal microscopy of carboxyfluorescein-filled axons showed that the rootlet neurones run out from the bases of the motor giant axons within the inner nerve ring and come into close contact with those of the neighbouring motor giant axons on either side. Transmission between the rootlet neurones has the properties of chemical synaptic transmission. A distinct type of fast excitatory postsynaptic potential (rootlet PSP) was recorded in motor giant axons following stimulation of nearby axons in 3-5 mmol l(-)(1) Mn(2+), which lowered the PSP below spike threshold. Immune labelling with anti-syntaxin 1 showed structures tentatively identified as synapses in the inner nerve ring, including some on the rootlet neurones. Neuromuscular junctions were not labelled. A secondary consequence of stimulating motor giant axons was the triggering of events in the pacemaker system. Triggering was blocked in 105 mmol l(-)(1) Mg(2+), indicating a synaptic link. Activity in the pacemaker system led indirectly to tentacle contractions (as described in earlier papers in this series), but the contractions were not as sudden or as violent as those seen when escape swimming was mediated by the ring giant axon. Events triggered in the pacemaker system fed back into the motor giants, producing postsynaptic potentials that appeared as humps in the spike after-potential. The conduction velocity of events propagating in the relay system was increased when the rootlet pathway was simultaneously excited (piggyback effect). With the addition of the rootlet pathway, the number of identified systems concerned with locomotion, feeding and tentacle contractions comes to fourteen, and the list is probably nearly complete.
G O Mackie; R W Meech
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  The Journal of experimental biology     Volume:  203     ISSN:  0022-0949     ISO Abbreviation:  J. Exp. Biol.     Publication Date:  2000 Jun 
Date Detail:
Created Date:  2000-08-11     Completed Date:  2000-08-11     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0243705     Medline TA:  J Exp Biol     Country:  ENGLAND    
Other Details:
Languages:  eng     Pagination:  1797-807     Citation Subset:  IM    
Biology Department, University of Victoria, British Columbia, Canada.
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MeSH Terms
Axons / physiology,  ultrastructure
Behavior, Animal
Fluorescent Dyes
Nervous System / ultrastructure
Neurons / ultrastructure
Scyphozoa / physiology*
Synaptic Transmission
Reg. No./Substance:
0/Fluoresceins; 0/Fluorescent Dyes; 3301-79-9/6-carboxyfluorescein

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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