Effects of intrathecal SNC80, a delta receptor ligand, on nociceptive threshold and dorsal horn substance p release

J Pharmacol Exp Ther. 2013 Nov;347(2):258-64. doi: 10.1124/jpet.113.206573. Epub 2013 Aug 26.

Abstract

Delta-opioid receptors (DOR) are present in the superficial dorsal horn and are believed to regulate the release of small afferent transmitters as evidenced by the effects of spinally delivered delta-opioid preferring peptides. Here we examined the effects of intrathecal SNC80 [(+)-4-[α(R)-α-[(2S,5R)-4-allyl-2,5-dimethyl-1-piperazinyl]-3-(methoxybenzyl)-N,N-diethylbenzamide], a selective nonpeptidic DOR agonist, in three preclinical pain models, acute thermal escape, intraplantar carrageenan-tactile allodynia, and intraplantar formalin flinches, and on the evoked release of substance P (SP) from small primary afferents. Rats with chronic intrathecal catheters received intrathecal vehicle or SNC80 (100 or 200 μg). Intrathecal SNC80 did not change acute thermal latencies or carrageenan-induced thermal hyperalgesia. However, SNC80 attenuated carrageenan-induced tactile allodynia and significantly reduced both phase 1 and phase 2 formalin-induced paw flinches, as assessed by an automatic flinch counting device. These effects were abolished by naltrindole (3 mg/kg i.p.), a selective DOR antagonist, but not CTOP (10 µg i.t.), a selective MOR antagonist. Furthermore, intrathecal SNC80 (200 μg) blocked formalin-induced substance P release otherwise evoked in the ispilateral superficial dorsal horn as measured by NK1 receptor internalization. In conclusion, intrathecal SNC80 alleviated pain hypersensitivity after peripheral inflammation in a fashion paralleling its ability to block peptide transmitter release from small peptidergic afferents, which by its pharmacology appears to represent an effect mediated by a spinal DOR.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Benzamides / administration & dosage
  • Benzamides / pharmacology*
  • Benzamides / therapeutic use
  • Disease Models, Animal
  • Injections, Spinal
  • Ligands
  • Male
  • Pain / drug therapy*
  • Pain / metabolism
  • Pain Threshold / drug effects*
  • Piperazines / administration & dosage
  • Piperazines / pharmacology*
  • Piperazines / therapeutic use
  • Posterior Horn Cells / drug effects*
  • Posterior Horn Cells / metabolism
  • Rats
  • Rats, Sprague-Dawley
  • Receptors, Neurokinin-1 / metabolism
  • Receptors, Opioid, delta / agonists*
  • Receptors, Opioid, delta / antagonists & inhibitors
  • Substance P / metabolism*
  • Substance P / pharmacology

Substances

  • Benzamides
  • Ligands
  • Piperazines
  • Receptors, Neurokinin-1
  • Receptors, Opioid, delta
  • 4-(alpha-(4-allyl-2,5-dimethyl-1-piperazinyl)-3-methoxybenzyl)-N,N-diethylbenzamide
  • Substance P