Cholinergic and non-cholinergic synaptic mechanisms in the aged rat hippocampus.

We compared age-related alterations in the electrophysiological and pharmacological properties of CA1 hippocampal pyramidal neurons in three strains of rats (Sprague-Dawley, Fisher 344 and Wistar) at 3-4 and 25-32 months of age, using the in vitro slice preparation. The most consistent age-related alterations were: a decrease in membrane excitability, a decrease in the amplitude and duration of inhibitory postsynaptic potentials and a decreased sensitivity to the effect of the cholinergic agonist carbachol. In contrast, no consistent alterations in calcium-dependent events were observed in these strains of rats. The age-related changes in the duration of the after-hyperpolarization (AHP) were different (and even opposite) depending on the strain studied. Our results show that age-related changes observed in a given strain are not necessarily present in all strains of the same species.