Background: It has been revealed that oxytocin (OT) plays an important role in pain modulation through oxytocin receptors (OTR) expressed by spinal and dorsal root ganglion (DRG) neurons. This study was designed to examine whether OT may modulate transient receptor potential vanilloid type 1 (TRPV1)/capsaicin receptor function through OTR signalisation in cultured DRG neurons. 
Aim: The possible cellular and molecular mechanisms of the antinociceptive effect of OT exerted through an action on primary sensory neurons which express the TRPV1 receptor were examined.
Materials and methods: Cell cultures were prepared from DRGs of adult male Wistar rats (n=9) weighing 250-310 g. Neurons responsive to capsaicin were identified by using the Co2+-uptake assay. 
Results: In the presence of 1 µM capsaicin 38±8.56 % of cultured DRG neurons exhibited staining after incubation in the Co2+-uptake assay buffer. Administration of OT or OT co-administered with Atosiban, an OTR antagonist, 10 min prior to the capsaicin challenge failed to affect the proportions of cobalt-labelled neurons significantly (35.78±4.87 and 31.51±7.96%, respectively). However, administration of oxytocin (1 µM) for 3 days resulted in a significant decrease in the proportion of neurons showing cobalt staining (28.45±4.2, p< 0.05, n=9), which was prevented by co-administration of Atosiban. 
Conclusion: The present findings indicate that OT may modulate the activation of the TRPV1 nociceptive ion channel in cultured DRG neurons. It is suggested that the modulatory role of OT effected through OTRs may bear of significance in the nociceptive and local regulatory/sensory-efferent functions of chemosensitive primary sensory neurons.
Supported by: GINOP-2.3.2-15-2016-00034.

TRPV1 RECEPTOR ACTIVATION BY CAPSAICIN IS MODULATED BY OXYTOCIN IN CULTURED DORSAL ROOT GANGLION NEURONS