Autoradiographic distribution of μ-, δ- and κ₁-opioid stimulated [³⁵S]guanylyl-5'-O-(γ-thio)-triphosphate binding in human frontal cortex and cerebellum

Opioid receptors are known to couple to G-proteins and to inhibit adenylyl cyclase. Receptor activation of G-proteins can be measured by agonist-stimulated [³⁵S]guanylyl-5'-O-(γ-thio)-triphosphate (GTPγS-) binding in brain sections to localize neuroanatomically functional coupling of receptors to intracellular signal transduction mechanisms. In the present study the selective μ-, δ- and κ₁-opioid agonists DAMGO ([D-Ala²,N-Me-Phe⁴,Gly-ol⁵]-enkephalin), DPDPE ([D-Pen^2,5]-enkephalin) and enadoline (CI-977) were used to stimulate [³⁵S]GTPγS-binding in human brain sections of frontal cortex and cerebellum. In human frontal cortex μ- and δ- opioid stimulated [³⁵S]GTPγS-binding was evenly distributed throughout the gray matter, while κ₁-opioid stimulated [³⁵S]GTPγS-binding was detected predominantly in lamina V and VI. In the cerebellar cortex stimulated [³⁵S]GTPγS-binding revealed functional coupling of μ- and κ₁-opioid receptors in the molecular layer. Copyright (C) 2000 Elsevier Science Ireland Ltd.