Pulsed Magnetic Field Induced “Analgesia” in the Land Snail, Cepaea nemoralis, and the Effects of μ, δ, and κ Opioid Receptor Agonists/Antagonists

Abstract

Thomas, A. W., M. Kavaliers, F. S. Prato and K.-P. Ossenkopp. Pulsed magnetic field induced “analgesia” in the land snail, Cepaea nemoralis, and the effects of μ, δ, and κ opioid receptor agonists/antagonists. Peptides 18(5) 703–709, 1997.—A brief exposure to a pulsed magnetic field (Cnp: patent pending) had significant antinociceptive or “analgesic” effects in the land snail, Cepaea nemoralis, as evidenced by an increase in the latency of response to a warmed (40°C) surface. This analgesia was in part opioid mediated being significantly reduced, but not eliminated: by the prototypic opiate antagonist, naloxone; the μ (mu) opioid receptor directed antagonists, naloxazine or β-funaltrexamine, and the δ (delta) opioid receptor directed antagonists, naltrindole-5′-isothiocyanate or ICI 174,864. However the Cnp induced analgesia was unaffected by the κ (kappa) opioid receptor directed antagonist, nor-binaltorphimine. The δ1 and δ2 opioid receptor directed agonists, (DPDPE, [D-Pen2,D-Pen5]enkephalin), (deltorphin, [D-Ala2,Glu4]), respectively, also had significant differential analgesic effects, supporting a functional δ opioid receptor mediated enkephalinergic mechanism in Cepaea. These results suggest that this specific pulsed magnetic field (Cnp) elicits significant analgesic effects through mechanisms that, in part, involve δ and, to a lesser extent, μ opioid receptors.