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Somatotopic organization and functional properties of mechanosensory neurons expressing sensorin‐A mRNA in Aplysia californica
Author(s) -
Walters Edgar T.,
Bodnarova Michaela,
Billy Allen J.,
Dulin Michael F.,
DíazRíos Manuel,
Miller Mark W.,
Moroz Leonid L.
Publication year - 2004
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/cne.20042
Subject(s) - receptive field , biology , aplysia , neuroscience , soma , electrophysiology , sensory system , somatosensory system , anatomy , stimulation , mechanoreceptor , sensory stimulation therapy
A previous study reported that a peptide, sensorin‐A, is expressed exclusively in mechanosensory neurons having somata in central ganglia of Aplysia . The present study utilized in situ hybridization, staining by nerve back‐fill and soma injection, and electrophysiological methods to characterize the locations, numbers, and functions of sensorin‐A‐expressing neurons and to define the relationships between soma locations and the locations of peripheral axons and receptive fields. Approximately 1,000 cells express sensorin‐A mRNA in young adult animals (10–30 g) and 1,200 cells in larger adults (100–300 g). All of the labeled somata are in the CNS, primarily in the abdominal LE, rLE, RE and RF, pleural VC, cerebral J and K, and buccal S clusters. Expression also occurs in a few sparsely distributed cells in most ganglia. Together, receptive fields of all these mechanosensory clusters cover the entire body surface. Each VC cluster forms a somatotopic map of the ipsilateral body, a “sensory aplunculus.” Cells in the pleural and cerebral clusters have partially overlapping sensory fields and synaptic targets. Buccal S cells have receptive fields on the buccal mass and lips and display notable differences in electrophysiological properties from other sensorin‐A‐expressing neurons. Neurons in all of the clusters have relatively high mechanosensory thresholds, responding preferentially to threatening or noxious stimuli. Synaptic outputs to target cells having defensive functions support a nociceptive role, as does peripheral sensitization following noxious stimulation, although additional functions are likely in some clusters. Interesting questions arise from observations that mRNA for sensorin‐A is present not only in the somata but also in synaptic regions, connectives, and peripheral fibers. J. Comp. Neurol. 471:219–240, 2004. © 2004 Wiley‐Liss, Inc.