[Abstract Title]. - Society for Neuroscience

Poster
271. Mechanoreceptors
Time: Sunday, November 16, 2008, 1:00 pm - 5:00 pm
Program#/Poster#: 271.2/HH21
Topic: D.09.a. Cellular and molecular mechanisms of transduction
Support: Canadian Institutes of Health Research
Dalhousie Medical Research Foundation
Nova Scotia Health Research Foundation
Title: Regional calcium changes in spider mechanoreceptors during sensory transduction
Authors: U. HOEGER, S. MEISNER, P. H. TORKKELI, *A. S. FRENCH;
Dept Physiol & Biophysics, Dalhousie Univ., Halifax, NS, Canada
Abstract: Intracellular Ca 2+ modulates mechanotransduction in auditory and vestibular hair
cells, where it enters through transduction channels and regulates dynamic sensitivity via several
mechanisms. There is also indirect evidence for Ca 2+ involvement in vertebrate cutaneous
mechanoreception, based on labeling of Ca 2+ pumps and Ca 2+ binding proteins. One modulating
mechanism found in both vertebrate and invertebrate mechanoreceptors is voltage dependent
negative feedback via Ca 2+ activated K + channels.
The compound slit sense organ VS-3 in the patella of the spider, Cupiennius salei, consists of 7-8
cuticular slits, each innervated by a pair of bipolar mechanosensory neurons. VS-3 neurons are
accessible to intracellular recording and mechanical stimulation in the periphery, where
mechanotransduction occurs. VS-3 neurons have a low voltage activated Ca 2+ current that can
produce action potentials when voltage-activated Na + and K + currents are blocked. During
mechanotransduction, Ca 2+ enters VS-3 neurons via voltage activated Ca 2+ channels when they
are opened by action potentials.
VS-3 neurons have three distinct regions in the periphery, comprising the sensory dendrites,
somata and axons. Some efferent modulation is differentially distributed to these three regions,
with octopamine and GABAA receptors primarily located on the somata and axons while
GABAB receptors are concentrated on dendrites and inhibitory glutamate receptors are present in
all regions.
Previous experiments showed that intracellular [Ca 2+ ] rises in all regions of VS-3 neurons during
continuous action potential firing but did not identify the regional distribution of Ca 2+ entry. We
have now used Ca 2+ sensitive fluorescence measurements to estimate the time course and
amplitude of intracellular [Ca 2+ ] changes in the three peripheral regions of VS-3 neurons