The uptake of serotonin and dopamine by homogenates of frozen rat and human brain tissue

A recently described procedure of freezing and thawing, which allows retention of metabolic and functional integrity, has been applied in the study of serotonin and dopamine uptake into frozen rat and post mortem human frozen tissue. TheK_m andV_max for the serotonin uptake into human hypothalamus were estimated to be 0.12 M and 0.03 nmol/g/min respectively. TheK_m andV_max for the dopamine uptake into human putamen were estimated to be 0.28 M and 0.13 nmol/g/min respectively. The results indicate that the freezing procedure does not affect the uptake sites for these transmitters. The storage time before freezing is however of importance for theV_max value. TheK_m value for the uptake, on the other hand, seems to be rather resistant to storage time before freezing.