Aim: 

The SAMP8 mouse is an accelerated-senescence model useful to evaluate aging impairments such as learning deficits. This study combines a classical conditioning eyeblink paradigm with a parallel evaluation of excitatory postsynaptic potentials (EPSP) fields evoked at the CA1-Prefrontal synapse to evaluate a hypothetical correlation between learning capabilities and accelerated aging in SAMP8 mice.

Methods: 

5-month-old SAMP8 (accelerated senescence) and SAMR1 (senescence resistant) mice were used. EMG recording electrodes were implanted in the orbicularis oculi muscle of the left upper eyelid. For classical conditioning of eyelid responses, we used a tone (20 ms; 6 kHz; 80 dB) as a conditioned stimulus. Bipolar stimulating electrodes were implanted on the ipsilateral supraorbitary branch of the trigeminal nerve for presentation of the unconditioned stimulus. Animals were also implanted with stimulating and recording electrodes aimed to activate CA1-Prefrontal synapses of the right (contralateral) hemisphere.

Results: 

Curves representing percent of conditioned responses corresponding to the different conditioning sessions presented levels in SAMR1 mice that duplicated the same set of data obtained from SAMP8 animals. Moreover, the amplitude of EPSP fields evoked during conditioning in SAMR1 mice, expressed as a percent of data collected during the first session (habituation), were increased in two folds until the last conditioning sessions, while EPSP fields from SAMP8 were not modified.

Conclusion: 

The CA1-Prefrontal synapses are involved in associative learning processes, and this process is impaired in the SAMP8 model of accelerated senescence.