L-Carnosine Dipeptide (β-Alanyl-L-Histidine): Cryoprotector of Nervous Tissue of Nonhibernating Animals

In this work the cryoprotective properties of the dipeptide L-carnosine (β-alanyl-L-histidine) on slices of the rat brain olfactory cortex are investigated. Changes in the activity of N-methyl-D-aspartate receptors, as the most vulnerable to the effects of cryopreservation (CP), were analyzed; for this purpose, the NMDA-synaptic component of the excitatory postsynaptic potential (abbreviated as NMDA potentials) was recorded extracellularly. The slices were incubated in a medium with L-carnosine (20 mM) and frozen at a slow rate (0.1°C/min) to –10°C, and after CP (30 days) they were warmed at the same rate (0.1°C/min) to 37°C. The effectiveness of L-carnosine for cryoprotection was determined by changes in the amplitudes of NMDA potentials after CP compared to before CP. The dipeptide restored the pH of the freezing medium (6.9, without L-carnosine) to optimal values (7.3–7.4), promoted the dehydration of free water from slices after CP, and inhibited the development of glutamate excitotoxicity in slices. The data obtained prove that L‑carnosine exhibits the properties of a non-toxic, effective cryoprotector in the nervous tissue of warm-blooded, non-hibernating animals.