The effects of postmortem delay on mu, delta and kappa opioid receptor subtypes in rat brain and guinea pig cerebellum evaluated by radioligand receptor binding

Abstract

Studies of human and animal central nervous system receptor degradation and measurement postmortem are important as human tissue can rarely be collected under ideal experimental conditions. Correlating the change in binding of opioid receptor subtypes over time will help define the conditions under which human studies may be valid. The present study was designed to investigate the rate at which opioid receptor subtypes degrade postmortem. Brains from rats or cerebelli from guinea pigs were kept at 22 °C or 4 °C at times from zero to 24 hours to simulate two common human collection techniques; room temperature and morgue refrigeration. Tissue homogenates from these brains were analysed for mu 1 mu 2, delta, kappa 1 and kappa 3 opioid receptor binding using standard radioligand binding techniques. At room temperature mu 1, mu 2 and delta opioid receptor binding was reduced between 6 and 12 hours, whereas kappa 1 and kappa 3 binding was reduced after 24 hours. At 4 °C mu 2, mu 2, delta, kappa 1 and kappa 3 binding remained constant over the 24 hour period.