Metabotropic purinoreceptors in rat dorsal horn neurones: predominant dendritic location

P2Y receptors and pain transmission

It is widely accepted that the most important ATP receptors involved in pain transmission belong to the P2X₃ and P2X_2/3 subtypes, selectively expressed in small diameter dorsal root ganglion (DRG) neurons. However, several types of the metabotropic ATP (P2Y) receptors have also been found in primary afferent neurons; P2Y₁ and P2Y₂ receptors are typically expressed in small, nociceptive cells. Here we review the results available on the involvement of P2Y receptors in the modulation of pain transmission.

Diabetes-induced abnormalities in ER calcium mobilization in primary and secondary nociceptive neurons

Development of diabetic sensory polyneuropathy is associated with alterations in intracellular calcium homeostasis in primary and secondary nociceptive neurons. We have shown previously that in a model of streptozotocin (STZ)-induced diabetes, the calcium signal is prolonged and calcium release from ryanodine-sensitive calcium stores down-regulated in neurons of the nociceptive system. The aim of the present study was a more detailed characterization of calcium homeostasis in primary (dorsal root ganglia, DRG) and secondary (dorsal horn, DH) nociceptive neurons in STZ-induced diabetes. Fluorescence video-imaging was used to measure free cytosolic [Ca2+] ([Ca2+]i) in lumbar nociceptive neurons of control and streptozotocin-diabetic rats. Resting [Ca2+]i rose progressively in these neurons with the duration of diabetes and calcium mobilization from the endoplasmic reticulum (ER) decreased during diabetes. The amplitude of calcium release from both ryanodine- and IP3-sensitive calcium stores induced by caffeine, ionomycin, ATP or glutamate was significantly (P<0.01) lower in DRG and DH neurons from 6-week STZ-diabetic rats. Diabetes-induced changes in the calcium homeostasis were similar in DRG and DH neurons indicating that they might be general for many types of neurons from the central and peripheral nervous systems.