High affinity choline uptake in striatum and hippocampus: Differential effects of treatments which release acetylcholine

We have compared the effect of treatments known to release acetylcholine (ACh) on high affinity choline (Ch) uptake in rat striatum and hippocampus. First, Ch uptake into synaptosome-rich P 2 fractions was measured after the systemic administration of drugs which increase ACh release. Pentylenetetrazol (75 mg/kg, i.p.) increased the uptake of Ch into hippocampal P 2 fractions by 45%. However, this treatment had no effect on striatal Ch uptake. Fluphenazine (0.5 or 5 mg/kg, s.c.), a drug which selectively increases ACh release in striatum, also failed to alter Ch uptake by tissue fractions prepared from that region. Second, P 2 fractions were incubated in a depolarizing, high potassium (62 mM) Krebs-Ringer phosphate buffer, after which Ch uptake was measured. This treatment increased hippocampal Ch uptake by 150%, while uptake into striatal tissue was increased by only 31%. The results of these studies suggest that in vitro Ch uptake is considerably less responsive in striatum than in hippocampus to the effects of prior alterations in ACh release. This is true whether alterations are induced in vivo or in vitro . These findings indicate that ACh synthesis may be regulated differently in the two brain regions.