eledoisin and Pain

The effect of unilateral sciatic nerve transection on behavioural responses produced by intrathecal administration of substance P (SP), neurokinin A, eledoisin and physalaemin was investigated in the rat. The injection of SP (3 nmol/rat) into the subarachnoid space was followed by reciprocal scratching, biting and licking of the fore- and hind-limbs. There was no observable difference in the behavioural response to SP between rats with nerve transection and sham operated rats at 5 days after operation. Whereas at 10, 20, and 30 days after nerve transection the response to SP was significantly increased as compared with sham operated rats. This phenomenon was also observed with neurokinin A (1.5, 3.0 and 6.0 nmol/rat), eledoisin (0.05 and 0.10 nmol/rat) and physalaemin (0.05 and 0.10 nmol/rat) at 10 days after operation. Ipsilateral depletion of SP from the lumbar (L4-L6) spinal cord was observed at 5, 10, 20, and 30 days after the unilateral transection of the sciatic nerve. These results suggest that sciatic nerve transection may produce an increased response to tachykinins through an enhanced sensitivity of tachykinin receptors in the lumbar cord.

Topics: Animals; Autacoids; Behavior, Animal; Denervation; Eledoisin; Injections, Spinal; Male; Neuropeptides; Pain; Peripheral Nerves; Physalaemin; Rats; Rats, Inbred Strains; Spinal Cord; Substance P; Tachykinins

The hyperalgesic effect of intrathecally administered substance P (SP), physalaemin, eledoisin and eledoisin-related peptide (ERP) was investigated in the rat tail flick test. Hyperalgesia produced by SP (2.5-15 micrograms, 1.9-11 nmol) was maximal 10-20 min after injection, lasted 30 min and was dose-related. The effect was mimicked by all of the peptides examined. The rank order of potency was physalaemin greater than SP greater than eledoisin greater than ERP. Desensitization to the hyperalgesic effect of SP was produced by three repeated intrathecal injections. Rats desensitized to SP no longer responded to physalaemin or ERP, indicating cross-desensitization. Phentolamine continued to produce hyperalgesia following such desensitization. The demonstration of a hyperalgesic effect for SP provides further support for a role for SP in nociceptive transmission. The receptor mediating this effect appears to be a SP-P subtype. Cross-desensitization between peptides suggests an action on the same receptor.

Topics: Animals; Drug Tolerance; Eledoisin; Injections, Spinal; Male; Nociceptors; Pain; Peptides; Physalaemin; Rats; Rats, Inbred Strains; Reaction Time; Substance P; Time Factors

Topics: Acetylcholine; Action Potentials; Adenosine; Adenosine Triphosphate; Angiotensin II; Animals; Blood Pressure; Drug Synergism; Ear; Eledoisin; Epinephrine; Female; Histamine; In Vitro Techniques; Male; Oxytocin; Pain; Peptides; Potassium Chloride; Prostaglandins; Rabbits; Respiration; Sensory Receptor Cells; Serotonin; Substance P; Time Factors; Vasoconstrictor Agents; Vasodilator Agents; Vasopressins; Venous Pressure

Topics: Acetylcholine; Age Factors; Analgesics; Animals; Atropine; Barium; Bradykinin; Catheterization; Chlorides; Diphenhydramine; Dogs; Eledoisin; Femoral Artery; Histamine; Mesenteric Arteries; Norepinephrine; Pain; Papaverine; Procaine; Salicylates; Serotonin; Tripelennamine; Vocalization, Animal

Topics: Adult; Bradykinin; Eledoisin; Female; Humans; Kallidin; Male; Pain