Hippocampal cholinergic hypofunction may contribute to memory deficits
following experimental traumatic brain injury. These studies examined
two important factors in acetylcholine synthesis: choline availabilit
y and neuronal uptake. No reductions in basal extracellular choline le
vels, using microdialysis, were observed 2 weeks after cortical impact
injury. However, studies of high affinity [H-3]choline uptake in the
hippocampus, measured in a synaptosomal preparation, found a reduction
in the maximum velocity of choline uptake (V-max), while no differenc
es in affinity constants (K-m) were found. The results suggest that po
st-traumatic cholinergic deficits are not attributable to decreased av
ailability of choline, but may be associated with either a decreased a
bility of cholinergic neurons to take up choline and/or a loss of chol
inergic neurons.