Swelling-activated calcium signalling in cultured mouse primary sensory neurons.
The effects of hypo-osmotic membrane stretch on intracellular calcium concentration ([Ca(2+)](i)), cell volume and cellular excitability were investigated in cultured mouse primary sensory trigeminal neurons. Hypotonic solutions (15--45%) led to rapid cell swelling in all neurons. Swelling was accompanied by dose-dependent elevations in [Ca(2+)](i) in a large fraction of neurons. Responses could be classified into three categories. (i) In 57% of the neurons [Ca(2+)](i) responses had a slow rise time and were generally of small amplitude. (ii) In 21% of the neurons, responses had a faster rise and were larger in amplitude. (iii) The remaining cells (22%) did not show [Ca(2+)](i) responses to hypo-osmotic stretch. Slow and fast [Ca(2+)](i) changes were observed in trigeminal neurons of different sizes with variable responses to capsaicin (0.5 microM). The swelling-induced [Ca(2+)](i) responses were not abolished after depletion of intracellular Ca2+ stores with cyclopiazonic acid or preincubation in thapsigargin, but were suppressed in the absence of external Ca(2+). They were strongly attenuated by extracellular nickel and gadolinium. Hypotonic stimulation led to a decrease in input resistance and to membrane potential depolarization. Under voltage-clamp, the [Ca(2+)](i) elevation produced by hypotonic stimulation was accompanied by the development of an inward current and a conductance increase. The time course and amplitude of the [Ca(2+)](i) response to hypo-osmotic stimulation showed a close correlation with electrophysiological properties of the neurons. Fast [Ca(2+)](i) responses were characteristic of trigeminal neurons with short duration action potentials and marked inward rectification. These findings suggest that hypo-osmotic stimulation activates several Ca(2+)-influx pathways, including Gd(3+)-sensitive stretch-activated ion channels, in a large fraction of trigeminal ganglion neurons. Opening of voltage-gated Ca(2+) channels also contributes to the response. The pattern and rate of Ca(2+) influx may be correlated with functional subtypes of sensory neurons.
Viana
F
F
Instituto de Neurociencias, Universidad Miguel Hernández-CSIC, Apartado 18, San Juan de Alicante 03550, Spain. felix.viana@umh.es
de la Peña
E
E
Pecson
B
B
Schmidt
R F
RF
Belmonte
C
C
D000818:Animals; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000187:drug effects; D020013:Calcium Signaling / Q000187:drug effects*; D002211:Capsaicin / Q000494:pharmacology; D002412:Cations / Q000494:pharmacology; D002462:Cell Membrane / Q000502:physiology; D048429:Cell Size; D002478:Cells, Cultured / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D005260:Female; D005682:Gadolinium / Q000494:pharmacology; D006982:Hypertonic Solutions / Q000494:pharmacology; D007038:Hypotonic Solutions / Q000494:pharmacology*; D017136:Ion Transport / Q000187:drug effects; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D009475:Neurons, Afferent / Q000145:classification / Q000187:drug effects / Q000502:physiology*; D009532:Nickel / Q000494:pharmacology; D009995:Osmosis; D018408:Patch-Clamp Techniques; D013314:Stress, Mechanical; D012668:Trigeminal Ganglion / Q000166:cytology
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D002412:Cations; D006982:Hypertonic Solutions; D007038:Hypotonic Solutions; D009532:Nickel; D005682:Gadolinium; D002211:Capsaicin; D002118:Calcium