Characterization of synaptosomal dopamine release in rat and human brain after post-mortem storage and cryopreservation.

In preparing pathobiochemical studies on [(3)H]dopamine (DA) release in post-mortem human brain, freezing methods were tested regarding their applicability for cryopreservation of brain tissue. An optimal method was to incubate pieces of the nucleus accumbens of rats or humans in 0.32 M sucrose containing 5% dimethylsulfoxide before freezing the brain material. After cryopreservation of these pieces in liquid nitrogen the synaptosomal K(+)-stimulated [(3)H]DA release was found to be unchanged in comparison with the values obtained before freezing. Moreover, the inhibition of K(+)-stimulated [(3)H]DA release by extracellular DA, which is mediated by DA autoreceptors, was also detectable after using this freezing method. During post-mortem storage of rat brains in situ for up to 48 h it was found that [(3)H]DA release changes occurred in dependence on storage temperature: at 2 degrees C no alteration was noted, however, at 22 degrees C a relatively rapid, biphasic exponential decrease was found. Furthermore, subchronic haloperidol pretreatment of rats did not have any influence on post-mortem changes of [(3)H]DA release and its modulation by DA autoreceptors. In conclusion, it seems that post-mortem human brain is suitable for investigating synaptosomal K(+)-stimulated [(3)H]DA release and its autoreceptor-mediated inhibition. For this end a suitable cryopreservation method is presented and a correction for post-mortem delay is proposed which is based on changes of [(3)H]DA release at 22 degrees C in rats.