[Met5]enkephalin and delta2-opioid receptors in the spinal cord are involved in the cold water swimming-induced antinociception in the mouse

Life Sci. 1997;61(7):PL81-6. doi: 10.1016/s0024-3205(97)00542-0.


Mice made cold water swimming (CWS: 4 degrees C, 3 min) produced an opioid-mediated antinociception. Experiments were designed to determine what types of opioid receptors and endogenous opioid peptides in the spinal cord are involved in the CWS-induced antinociception in male ICR mice. Antinociception was measured by the tail-flick test. CWS-induced antinociception was blocked by intrathecal (i.t.) pretreatment with antiserum to [Met5]enkephalin (100 microg, 1 hr), but not by antiserum (100 microg, 1 hr) to [Leu5]enkephalin, beta-endorphin or dynorphin A (1-17). Moreover, i.t. pretreatment with delta2-opioid receptor antagonist naltriben (NTB: 10 microg, 10 min) blocked the antinociception induced by CWS or i.t.-administered [Met5]enkephalin (10 microg). However, the antinociception induced by CWS or i.t.-administered [Met5]enkephalin was not blocked by i.t. pretreatment with delta1-opioid receptor antagonist 7-benzylidene naltrexone (BNTX: 1 microg, 10 min), mu-opioid receptor antagonist D-Phe-Cys-Try-D-Try-Om-Thr-Phe-Thr-NH2 (CTOP: 50 ng, 10 min), or kappa-opioid receptor antagonist norbinaltorphimine (norBNI: 5 microg, 24 hr). These data indicate that [Met5]enkephalin and delta2-opioid receptor in the spinal cord are involved in antinociception induced by CWS.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Cold Temperature
  • Dynorphins / immunology
  • Enkephalin, Leucine / immunology
  • Enkephalin, Methionine / immunology
  • Enkephalin, Methionine / physiology*
  • Immune Sera
  • Injections, Spinal
  • Male
  • Mice
  • Mice, Inbred ICR
  • Pain / physiopathology*
  • Receptors, Opioid, delta / antagonists & inhibitors
  • Receptors, Opioid, delta / physiology*
  • Receptors, Opioid, kappa / antagonists & inhibitors
  • Receptors, Opioid, mu / antagonists & inhibitors
  • Spinal Cord / drug effects
  • Spinal Cord / physiology*
  • beta-Endorphin / immunology


  • Immune Sera
  • Receptors, Opioid, delta
  • Receptors, Opioid, kappa
  • Receptors, Opioid, mu
  • Enkephalin, Methionine
  • Enkephalin, Leucine
  • beta-Endorphin
  • Dynorphins