Strain-dependent and stress-induced changes in rat hippocampal cholinergic system

The study demonstrates that in the hippocampus of inbred Wistar-Kyoto (WKY) rats [³H]choline uptake is 38% higher than in Brown-Norway (BN) rats. In contrast, the maximum binding capacity of [³H]quinuclidinylbenzilate (QNB) is 28% lower in WKY than in BN rats. After immobilization stress there is a reduction in [³H]choline accumulation which is more pronounced in WKY rats. Furthermore, maximal QNB binding after stress is increased only in WKY rats. Choline acetyltransferase activity, which was 83.5% higher in WKY rats, was not altered after stress in both strains. We conclude that: (1) choline accumulation is directly related to choline acetyltransferase activity in hippocampal synaptosomes; (2) maximum cholinergic muscarinic binding capacity is inversely related to the above two presynaptic activities and (3) immobilization stress results in a decreased choline accumulation and may lead to an increased QNB binding. The results imply that reduction in choline accumulation may be a compensatory mechanism of cholinergic synapses during adaptation to lenghty periods of neuronal activity.