The analgesic and toxic effects of nornicotine enantiomers alone and in interaction with morphine in rodent models of acute and persistent pain

Pharmacol Biochem Behav. 2010 Jan;94(3):352-62. doi: 10.1016/j.pbb.2009.09.017. Epub 2009 Oct 2.

Abstract

Neuronal nicotinic acetylcholinic receptors (nAChR) are promising targets for the development of novel analgesics. Nicotine and other nAChR-agonists produce profound analgesia in rodent models of acute and persistent pain. However, significant side-effects are of concern. Nornicotine (N-desmethyl-nicotine) appears to activate different nAChR subtypes, has a better pharmacokinetic profile, and produces less toxicity than nicotine. Little is known about its analgesic properties. In the present study, the S(-)- and R(+)-enantiomers of nornicotine were characterized with regard to analgesia and side-effects profile. Efficacy was demonstrated in rat models of pain where central sensitization is involved: i.e. the chronic constriction nerve injury model of peripheral neuropathy and the formalin model of tonic inflammatory pain. The desirable (analgesic) properties resided predominantly in the S(-)- rather than the R(+)-enantiomer. In contrast, undesirable effects (motor in-coordination, reduced locomotor activity, ataxia) were more pronounced with the R(+)-enantiomer. This is an interesting finding, which may suggest separation of toxicity from analgesia by utilization of S(-)-enantiomer of nornicotine. Maximum analgesic effectiveness without significant side-effects was achieved when S(-)-nornicotine (sub-analgesic dose) was combined with a low-dose of the micro-opioid, morphine. These preclinical data suggest that S(-)-nornicotine may be of value, either alone or in combination with an opioid, for treatment of a broad-spectrum of pain (i.e. nociceptive, neuropathic, and mixed pain).

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acute Disease
  • Analgesics / administration & dosage
  • Analgesics / therapeutic use*
  • Analgesics / toxicity
  • Animals
  • Chronic Disease
  • Disease Models, Animal
  • Drug Interactions
  • Male
  • Morphine / administration & dosage
  • Morphine / therapeutic use*
  • Motor Activity / drug effects
  • Nicotine / administration & dosage
  • Nicotine / analogs & derivatives*
  • Nicotine / chemistry
  • Nicotine / therapeutic use
  • Nicotine / toxicity
  • Pain / drug therapy*
  • Rats
  • Rats, Sprague-Dawley
  • Stereoisomerism

Substances

  • Analgesics
  • Nicotine
  • Morphine
  • nornicotine