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Role of [Ca2+]i in the ATP-induced Heat Sensitization Process of Rat Nociceptive Neurons

Role of [Ca2+]i in the ATP-induced Heat Sensitization Process of Rat Nociceptive Neurons

M Kress, S Guenther

J Neurophysiol. 1999 Jun;81(6):2612-9.

PMID: 10368381

Abstract:

In inflamed tissue, nociceptors show increased sensitivity to noxious heat, which may account for heat hyperalgesia. In unmyelinated nociceptive afferents in rat skin in vitro, a drop of heat threshold and an increase in heat responses were induced by experimental elevation of intracellular calcium ([Ca2+]i) levels with the calcium ionophore ionomycin (10 microM). Similar results were obtained in experiments employing [Ca2+]i release from preloaded "caged calcium" (NITR-5/AM) via UV photolysis. In both cases, sensitization was prevented by preventing rises in [Ca2+]i with the membrane-permeant calcium chelator BAPTA-AM (1 mM). No pronounced change of mechanical sensitivity was observed. Heat-induced membrane currents (Iheat) were investigated with patch-clamp recordings, and simultaneous calcium measurements were performed in small sensory neurons isolated from adult rat dorsal root ganglia (DRG). Ionomycin-induced rises in [Ca2+]i resulted in reversible sensitization of Iheat. In the same subset of DRG neurons, the endogenous algogen ATP (100 microM) was used to elevate [Ca2+]i, which again resulted in significant sensitization of Iheat. In correlative recordings from the skin-nerve preparation, ATP induced heat sensitization of nociceptors, which again could be blocked by preincubation with BAPTA-AM. Rises in [Ca2+]i in response to inflammatory mediators, e.g., ATP, thus appear to play a central role in plastic changes of nociceptors, which may account for hypersensitivity of inflamed tissue.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
AP209161739	Nitr 5/AM		209161-73-9	Price

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