Proceedings of The Physiological Society
University College Dublin (2009) Proc Physiol Soc 15, PC67
Oxytocin provokes increase of free intracellular Ca2+ levels in freshly isolated rat sensory neurons
M. Ozcan1, S. Kutlu2, E. Alcin2, B. Yilmaz3, H. Kelestimur2, A. Ayar4
1. Biophysics, Firat University Medical School, Elazig, Turkey. 2. Physiology, Firat University Medical School, Elazig, Turkey. 3. Physiology, Yeditepe University Medical School, Istanbul, Turkey. 4. Physiology, Karadeniz Technical University, Trabzon, Turkey.
Although the cellular mechanisms remain unclear, available evidence indicates that beside its essential role in mammalian parturition and lactation the nonapeptide hormone oxytocin (OXT) plays an important role in nociceptive modulation (1). Evidence has accumulated that free intracellular calcium ([Ca2+]i) plays an important role in signal transduction to control a wide variety of cellular mechanisms including nociceptive transmission. Previous studies have also shown that OXT receptor is expressed in dorsal root ganglia (DRG) and in spinal dorsal horn. Hence, the present study was undertaken to investigate the possible effects of OXT on antinociception in freshly isolated rat dorsal root ganglion (DRG) neurons. Isolated DRG neurons were plated on coated cover slips following mechanical isolation and responses to OXT was studied by monitoring changes in [Ca2+]i with a microscopic digital image analysis system in fura-2 loaded single neurons. Data were analyzed by using unpaired t test, with a 2-tailed P level of <0.05 defining statistical significance. The majority of the DRG neurons (small, medium and large) responded by increase in [Ca2+]i to extracellular application of OXT concentration-dependently. The mean 340/380 nm ratio was 0.80±0.04 (baseline, n=7), 0.92±0.06 (30nM OXT, P<0.05, n=7) and 0.81±0.04 (baseline, n=27), 1.29±0.07 (100nM OXT, P<0.001, n=27), respectively. The stimulatory effect of OXT (100nM) was persistent in Ca2+-free conditions (Baseline: 0.90±0.07 vs. 100nM OXT: 1.06±0.06, n=5). We demonstrated first time that OXT evoked a robust increase of [Ca2+]i in freshly isolated rat DRG neurons. Although the physiological significance of the results obtained from this study remains to be elucidated, in agreement with previous studies our results indicates that OXT could modulate the somatosensory transmission (nociceptive or non-nociceptive) via inhibiting ATP receptor function (2) and/or enhancement of GABA effect currents in cultured rat sensory neurons.
Where applicable, experiments conform with Society ethical requirements