Influence of cooling rate on activity of ionotropic glutamate receptors in brain slices at hypothermia

• AMPA- and NMDA-dependent synaptic activity depends on cooling rate at hypothermia.
• Low rate of cooling promotes the nerve cell adaptation at hypothermia.
• Low cooling rate preserves the plasticity in the brain tissue.

Hypothermia is a known approach in the treatment of neurological pathologies. Mild hypothermia enhances the therapeutic window for application of medicines, while deep hypothermia is often accompanied by complications, including problems in the recovery of brain functions. The purpose of present study was to investigate the functioning of glutamate ionotropic receptors in brain slices cooled with different rates during mild, moderate and deep hypothermia. Using a system of gradual cooling combined with electrophysiological recordings in slices, we have shown that synaptic activity mediated by the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid and N-methyl-D-aspartate receptors in rat olfactory cortex was strongly dependent on the rate of lowering the temperature. High cooling rate caused a progressive decrease in glutamate receptor activity in brain slices during gradual cooling from mild to deep hypothermia. On the contrary, low cooling rate slightly changed the synaptic responses in deep hypothermia. The short-term potentiation may be induced in slices by electric tetanization at 16  °C in this case. Hence, low cooling rate promoted preservation of neuronal activity and plasticity in the brain tissue.