Regional high affinity synaptosomal transport of choline in mouse brain — Influence of oxotremorine treatment

Abstract

Kinetic parameters for high affinity [HA] uptake in vitro in synaptosomes from different mouse brain regions were investigated. V max was highest in the striatum [200 pmol.· mg protein −1 · 4 min −1], followed by the cortex [111 pmol · mg protein −1 · 4 min −1], hippocampus [63 pmol · mg protein −1 · 4 min −1], midbrain [21 pmol · mg protein −1 · 4 min −1] and, lowest, medulla oblongata [5 pmol · mg protein −1 · 4 min −1]. K m was about the same in all brain regions [0.9–1.4 μM]. No sign of HA uptake was detected in synaptosomes from the cerebellum. A clear relationship between V max for synaptosomal HA uptake of Ch in vitro and apparent turnover of ACh in vivo was found between the brain regions. Administration of oxotremorine [1 mg·kg −1 i.p.] decreased V max for HA uptake of Ch by 60% in the cortex and hippocampus, by 50% in the striatum and by 20% in the midbrain. This effect is in accordance with the previously observed marked decrease in turnover of ACh in these brain regions following oxotremorine treatment.