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

Area of Science:

• Neuroscience
• Neurochemistry
• Pharmacology

Background:

• Cholinergic system function is crucial for cognitive processes.
• Differences in neurotransmitter systems may underlie strain-specific behaviors and stress responses.
• Understanding presynaptic and postsynaptic adaptations is key to neurobiology.

Purpose of the Study:

• To investigate strain differences in hippocampal cholinergic parameters between Wistar-Kyoto (WKY) and Brown-Norway (BN) rats.
• To examine the effects of immobilization stress on these cholinergic parameters.
• To explore the relationship between choline uptake, choline acetyltransferase activity, and muscarinic receptor binding.

Main Methods:

• Measurement of [3H]choline uptake in hippocampal synaptosomes.
• Quantification of [3H]quinuclidinylbenzilate (QNB) binding to muscarinic receptors.
• Assay of choline acetyltransferase (ChAT) activity.
• Comparison between WKY and BN rat strains before and after immobilization stress.

Main Results:

• WKY rats showed significantly higher [3H]choline uptake (+38%) and lower maximal QNB binding (-28%) in the hippocampus compared to BN rats.
• Immobilization stress reduced [3H]choline accumulation more profoundly in WKY rats.
• Maximal QNB binding increased post-stress exclusively in WKY rats.
• Choline acetyltransferase activity was higher in WKY rats but unaffected by stress in either strain.

Conclusions:

• Hippocampal choline accumulation correlates positively with choline acetyltransferase activity.
• Maximal muscarinic cholinergic binding capacity is inversely related to presynaptic cholinergic activity.
• Immobilization stress decreases choline accumulation and may increase QNB binding, potentially as a compensatory mechanism for cholinergic synapses during prolonged neuronal activity.