Heterogeneity of Opioid Binding Sites in Guinea Pig Spinal Cord
Uniformed Services University Of The Health Sciences Bethesda United States
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High concentrations of opioid peptides derived from both proenkephalin and prodynorphin are present in spinal cord, and studies of their localization within spinal cord suggest the opioids may be involved in the regulation of both sensory and motor functions. Sensory deficits and disturbed motor functions following the local administration of opiates or opioid peptides to spinal cord also suggest a multiplicity of endogenous opioid regulatory functions In this tissue. Studies of radiolabelled opioid ligand binding to both regional sections or whole spinal cord membrane preparations confirm that saturable high affinity binding sites In this tissue show heterogeneity of binding properties. However, many of these studies have been conducted at non-physiological temperatures and in buffers lacking major physiological cations. Past studies have shown that opioid receptor binding is significantly affected the by presence of major physiologic cations as well as by venations in temperature. In this study of radiolabelled saturable high affinity stereoselective specific binding sites in whole spinal cord as well as lumbo-sacral spinal cord, conditions which parallel the in vivo situation were adhered to as closely as possible.