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Phorbol ester blocks the increase of a high affinity GTPase activity induced by delta 2-opioid receptor agonist in
M Narita1, H Mizoguchi, L F Tseng
1Department of Anesthesiology, Medical College of Wisconsin, Milwaukee, USA.
Abstract:
The high affinity GTPase activity in the mouse spinal cord was increased in a concentration-dependent manner by a selective delta 2-opioid receptor agonist, [D-Ala2]deltorphin II (0.1-1 microM). This increase of GTPase activity induced by [D-Ala2]deltorphin II was completely blocked by co-incubation with a selective delta 2-opioid receptor antagonist, naltriben (0.1 microM). A protein kinase C activator, phorbol 12,13-dibutyrate (PDB; 0.1-10 microM), which given alone had no effect on basal GTPase activity, blocked dose-dependently the increase of GTPase activity induced by [D-Ala2]deltorphin II (1 microM). Our results indicate the possibility that activation of protein kinase C by phorbol ester uncouples the delta 2-opioid receptor from G-proteins in the spinal cord.