Regulation of N-type calcium channels by nociceptin receptors and its possible role in neurological disorders.

Activation of nociceptin opioid peptide receptors (NOP, a.k.a. opioid-like receptor-1, ORL-1) by the ligand nociceptin/orphanin FQ, leads to G protein-dependent regulation of Cav2.2 (N-type) voltage-gated calcium channels (VGCCs). This typically causes a reduction in calcium currents, triggering changes in presynaptic calcium levels and thus neurotransmission. Because of the widespread expression patterns of NOP and VGCCs across multiple brain regions, the dorsal horn of the spinal cord, and the dorsal root ganglia, this results in the alteration of numerous neurophysiological features. Here we review the regulation of N-type calcium channels by the NOP-nociceptin system in the context of neurological conditions such as anxiety, addiction, and pain.

Analgesic effect in rodents of native and recombinant Ph alpha 1beta toxin, a high-voltage-activated calcium channel blocker isolated from armed spider venom.

Calcium influx through neuronal voltage-sensitive calcium channels (VSCC S) mediates nociceptive information in the spinal dorsal horn. In fact, spinally administered VSCC S blockers, such as omega-conotoxin MVIIA, have analgesic effect apart of their low therapeutic index and many side effects. Here we study the analgesic potential of Ph alpha 1beta, a calcium channel blocker, in rodent models of acute and persistent pain. Spinally administered Ph alpha 1beta showed higher efficacy and long-lasting analgesia in a thermal model of pain, when compared with omega-conotoxin MVIIA. Moreover, Ph alpha 1beta was more effective and potent than omega-conotoxin MVIIA not only to prevent, but especially to reverse, previously installed persistent chemical and neuropathic pain. Furthermore, the analgesic action of both toxins are related with the inhibition of Ca2+-evoked release of pro-nociceptive neurotransmitter, glutamate, from rat spinal cord synaptosomes and decrease of glutamate overflow in cerebrospinal fluid. When side effects were assessed, we found that Ph alpha 1beta had a therapeutic index wider than omega- conotoxin MVIIA. Finally, recombinant Ph alpha 1beta expressed in Escherichia coli showed marked analgesic activity similar to the native toxin. Taken together, the present study demonstrates that native and recombinant Ph alpha 1beta have analgesic effects in rodent models of pain, suggesting that this toxin may have potential to be used as a drug in the control of persistent pathological pain.