Endothelin-1 induced desensitization in primary afferent neurons.

Endothelin-1 (ET-1) is a known algogen that causes acute pain and sensitization in humans and spontaneous nociceptive behaviors when injected into the periphery in rats, and is elevated during vaso-occlusive episodes (VOEs) in sickle cell disease (SCD) patients. Previously, our lab has shown that a priming dose of ET-1 produces sensitization to capsaicin-induce secondary hyperalgesia. The goal of this study was to determine if the sensitization induced by ET-1 priming is occurring at the level of the primary afferent neuron. Calcium imaging in cultured dorsal root ganglion (DRG) neurons was utilized to examine the effects of ET-1 on primary afferent neurons. ET-1 induces [Ca(2+)]i transients in unprimed cells. ET-1 induced [Ca(2+)]i transients are attenuated by priming with ET-1. This priming effect occurs whether the priming dose is given 0-4 days prior to the challenge dose. Similarly, ET-1 priming decreases capsaicin-induced [Ca(2+)]i transients. At the level of the primary afferent neuron, ET-1 priming has a desensitizing effect on challenge exposures to ET-1 and capsaicin.