Korean J Otolaryngol-Head Neck Surg.  2003 Mar;46(3):191-197.

The Effects of Neurotransmitters on the Ion Channels in the Isolated Deiters'Cells of Guinea Pig Cochlea

• Nam EC
• Kim WT
• Leem CH
• Chung JW

Abstract

BACKGROUND AND OBJECTIVES
The supporting cells in the organ of Corti help to maintain the structural integrity of the organ, but it has been suggested that they also actively participate in regulating sound transduction. The existence of neural control was implied by the finding of efferent synapses in Deiters' cells, and the fact that the intracellular Ca2+ concentration was increased by the application of neurotransmitters, such as ATP (adenosine triphosphate) and Ach (acetylcholine), resulting in movement of the phalangeal processes of the Deiters' cells. This study investigated the effects of neurotransmitters on the ion channels in Deiters' cells. MATERIALS AND METHOD: Deiters' cells were isolated from guinea pig organs of Corti using collagenase and pipettes. Whole-cell patch clamps were performed under an inverted microscope and the current was measured with pClamp 8.0.2 software. RESULTS: The resting membrane potential was -21.1+/-3.5 mV. ATP (100 microM) treatment depolarized the potential to -3.1+/-1.1 mV, while the same concentration of Ach had no effect on the resting potential. In the voltage-clamping condition, the holding potential was 0 mV, and then a -80 mV pre-pulse was applied for 500 ms, followed by step pulses from -140 to +10 mV. Under these conditions, 10 microM ATP increased the inward current from -14.9+/-1.9 to -163.5+/-14.9 pA/pF at the maximal stimulus of -140 mV (n=4). In the current-voltage curve, the reversal potential was around -20 mV. Neither Ach nor carbachol induced current responses. The co-application of suramin (30 microM) and ATP (10 microM) suppressed the ATP-induced currents by 50%, and 30 microM of PPADS (pyridoxal-phosphate- 6-azophenyl-2, 4-disulphonic acid) inhibited the current almost to the level of the control. The purinoceptor-agonist, alpha, beta-meATP (alpha, beta-methylene adenosine triphosphate), 30 microM increased the inward current from -16.2+/-2.9 to -27.7+/-3.8 pA/pF, which was much smaller than the ATP-induced change. CONCLUSION: ATP-gated purinergic receptors may play an important role in regulating sound transduction by inducing an inward current and depolarizing the Deiters' cell membrane.

Keyword

Labyrinth supporting cell; Neurotransmitters; Ion channels; Purinergic receptors

MeSH Terms

Adenosine
Adenosine Triphosphate
Animals
Carbachol
Cell Membrane
Cochlea*
Collagenases
Guinea Pigs*
Guinea*
Ion Channels*
Labyrinth Supporting Cells
Membrane Potentials
Neurotransmitter Agents*
Organ of Corti
Receptors, Purinergic
Suramin
Synapses
Adenosine
Adenosine Triphosphate
Carbachol
Collagenases
Ion Channels
Neurotransmitter Agents
Receptors, Purinergic
Suramin