? and ? Opiate receptors in primary astroglial cultures from rat cerebral cortex

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Abstract
The effects of μ, δ, and κ receptor-agonists on forskolin stimulated cyclic adenosine-3′, 5′-monophosphate (cAMP) formation were examined in astroglial enriched primary cultures from the cerebral cortex of newborn rats. Intracellular cAMP accumulation was quantified by radioimmunoassay. Morphine was used as a μ-receptor agonist, D-Ala-D-Leu-Enkephalin (DADLE) as a δ-receptor agonist and dynorphine 1–13 (Dyn) as a κ-receptor agonist. Basal cAMP levels were unaffected by either the opiate agonists or the antagonists used. In the presence of the cAMP stimulator forskolin, morphine had no significant effect on the cytoplasmic cAMP levels. DADLE caused a dose related inhibition of the forskolin stimulated cAMP accumulation. The effects of this δ receptor stimulation was blocked with the selective antagonist ICI 174.864. In the presence of Dyn, the forskolin stimulated cAMP accumulation was inhibited in a dose related manner. This κ receptor stimulation was blocked with the selective antagonist MR 2266. Co-administration of DADLE and Dyn resulted in a non additive inhibition of the forskolin stimulated accumulation of cAMP. These findings indicate that astroglial enriched cultures from the cerebral cortex of rats express δ and κ-receptors co-localized ont he same population of cells, and that these receptors are inhibitory coupled to adenylate cyclase.