The S cell: an interneuron essential for sensitization and full dishabituation of leech shortening.
Sensory neurons in the leech excite the S interneuron, which in turn excites motoneurons that shorten the leech, although activity in the S cell reportedly cannot by itself shorten the animal. Experiments were performed in semi-intact leeches using established dishabituation and sensitization protocols. S-cell activity increased during reflexive shortening once the animal was sensitized or dishabituated with a strong shock. S-cell activity otherwise was not associated with shortening. To test the role of the S-cell in dishabituation and sensitization of the shortening reflex, single S cells were ablated in vivo by intracellular injections of pronase. S-cell lesions reduced but did not eliminate dishabituation; however, sensitization was completely disrupted. This was consistent with recent evidence that separate processes contribute to dishabituation and sensitization. Since the S cell in each ganglion is a link in a rapidly conducting chain along the length of the animal, it may be sufficient to break the chain at a single point to eliminate sensitization.
Sahley
C L
CL
Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907.
Modney
B K
BK
Boulis
N M
NM
Muller
K J
KJ
D000818:Animals; D001522:Behavior, Animal / Q000502:physiology; D006185:Habituation, Psychophysiologic / Q000502:physiology*; D007395:Interneurons / Q000502:physiology*; D007858:Learning / Q000502:physiology; D007865:Leeches / Q000502:physiology*