Calcium signaling in intact dorsal root ganglia: new observations and the effect of injury. Anesthesiology 2010 Jul;113(1):134-46
Date
06/08/2010Pubmed ID
20526180Pubmed Central ID
PMC3707925DOI
10.1097/ALN.0b013e3181e0ef3fScopus ID
2-s2.0-77954175043 (requires institutional sign-in at Scopus site) 24 CitationsAbstract
BACKGROUND: Ca is the dominant second messenger in primary sensory neurons. In addition, disrupted Ca signaling is a prominent feature in pain models involving peripheral nerve injury. Standard cytoplasmic Ca recording techniques use high K or field stimulation and dissociated neurons. To compare findings in intact dorsal root ganglia, we used a method of simultaneous electrophysiologic and microfluorimetric recording.
METHODS: Dissociated neurons were loaded by bath-applied Fura-2-AM and subjected to field stimulation. Alternatively, we adapted a technique in which neuronal somata of intact ganglia were loaded with Fura-2 through an intracellular microelectrode that provided simultaneous membrane potential recording during activation by action potentials (APs) conducted from attached dorsal roots.
RESULTS: Field stimulation at levels necessary to activate neurons generated bath pH changes through electrolysis and failed to predictably drive neurons with AP trains. In the intact ganglion technique, single APs produced measurable Ca transients that were fourfold larger in presumed nociceptive C-type neurons than in nonnociceptive Abeta-type neurons. Unitary Ca transients summated during AP trains, forming transients with amplitudes that were highly dependent on stimulation frequency. Each neuron was tuned to a preferred frequency at which transient amplitude was maximal. Transients predominantly exhibited monoexponential recovery and had sustained plateaus during recovery only with trains of more than 100 APs. Nerve injury decreased Ca transients in C-type neurons, but increased transients in Abeta-type neurons.
CONCLUSIONS: Refined observation of Ca signaling is possible through natural activation by conducted APs in undissociated sensory neurons and reveals features distinct to neuronal types and injury state.
Author List
Gemes G, Rigaud M, Koopmeiners AS, Poroli MJ, Zoga V, Hogan QHAuthor
Quinn H. Hogan MD Professor in the Anesthesiology department at Medical College of WisconsinMESH terms used to index this publication - Major topics in bold
Action PotentialsAnimals
Calcium Channel Blockers
Calcium Channels
Calcium Signaling
Cytophotometry
Fura-2
Ganglia, Spinal
Hydrogen-Ion Concentration
Male
Membrane Potentials
Nerve Fibers
Neurons, Afferent
Rats
Rats, Sprague-Dawley
Sensory Receptor Cells
