Effect of Comenic Acid on the Activation of G Proteins by Agonists of Opioid Receptors in Plasma Membranes from the Rat Brain

Author： Kazakov V. N. Panova T. I. Tsyvkin V. N. Prudnikov I. M.

Publisher： Springer Publishing Company

ISSN： 0090-2977

Source： Neurophysiology, Vol.36, Iss.1, 2004-01, pp. : 10-15

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Abstract

We studied the effect of comenic acid on transmembrane opioid signaling (in particular, on that mediated by δ-opioid receptors, with the use of an agonist of these receptors, [D-Ala²]-leucine enkephalin (DALE), and mediated by μ-opiate receptors, with the use of morphine). It was demonstrated that comenic acid modulates agonist-dependent binding of [³⁵S]GTPγS in plasma membranes from the rat brain. The effect of comenic acid on the activation of G proteins via δ-opioid receptors possessing high affinity for DALE depended on the ion composition of the medium: in the presence of K⁺ the activation decreased, while in the presence of Na⁺ it remained invariable. Under the influence of comenic acid, the agonist-dependent activation of G proteins mediated by receptors with low affinity for DALE was intensified in the presence of both Na⁺ and K⁺. Using morphine, we observed opposite effects: in the presence of Na⁺ or K⁺ comenic acid decreased or increased, respectively, the agonist-dependent activation of G proteins. We suggest that due to the comenic acid-induced modulation the relative intensity of activation of G proteins, which control signal pathways activated by opioid receptors of different types, can be significantly changed.