Cocaine and cocaethylene binding to normal human brain and Alzheimer disease brain

The binding of cocaine and cocaethylene to homogenates of both normal whole brain and whole brain with Alzheimer disease patients (Alzheimer brain) was investigated in vitro using equilibrium dialysis of the unlabelled drugs at 4 degrees C. Two binders of cocaine were characterized in normal brain (binder 1: Ka, 5.73 x 10(3) L/mol; Bo, 7.44 x 10(-5) mol/L) (binder 2: Ka, 1.54 x 10(3) L/mol; Bo, 2.50 x 10(-4) mol/L) and in Alzheimer brain (binder 1: Ka, 3.08 x 10(2) L/mol; Bo, 6.66 x 10(-4) mol/L) (binder 2: Ka, 8.74 x 10(1) L/mol; Bo, 4.30 x 10(-3) mol/L). For cocaethylene three binders were noted in normal brain (binder 1: Ka, 3.23 x 10(3) L/mol; Bo, 1.22 x 10(-4) mol/L) (binder 2: Ka, 3.10 x 10(3) L/mol; Bo, 2.01 x 10(-4) mol/L) (binder 3: Ka, 1.63 x 10(3) L/mol; Bo, 3.59 x 10(-4) mol/L) and two binders in Alzheimer brain (binder 1: Ka, 5.18 x 10(3) L/mol; Bo, 3.06 x 10(-5) mol/L) (binder 2: Ka, 3.36 x 10(3) L/mol; Bo, 7.75 x 10(-5) mol/L). The binding of cocaine to normal brain was much stronger than to Alzheimer brain (ten- to 100-fold), whereas the binding of cocaethylene was similar in normal and Alzheimer brain. Cocaine and cocaethylene binding to human brain was compared with cocaine and cocaethylene binding to other human tissues previously studied by this laboratory.