Effect of Myelopeptide 2 on Addiction Memory in the Mouse

As is known, myelopeptides (MPs) influence the formation of long-term post-tetanic potentiation (LTP)—that is, they affect synaptic plasticity. To investigate the effect of MPs on the formation of addictive memory, we employed a morphine-induced conditioned place preference (CPP).

The experiment was conducted on male C57BL/6 inbred mice. Morphine hydrochloride (10 mg/kg, 100 µL) and MP2 (2 µg/kg, 50 µL) were dissolved in sterile 0.9% NaCl and administered intraperitoneally.  CPP was established using a standard protocol for morphinization.  Extracellular recording of excitatory postsynaptic potentials (EPSPs) was performed using glass microelectrodes placed in the stratum radiatum of the hippocampal slices CA1 region. Stimuls were applied to the Schaffer collateral region.

In control conditions, the amplitude of the field EPSP increased in 1.5 time after tetanization and remained elevated for 60 minutes or longer. Administration of MP2 during the conditioning phase blocked the acquisition of the conditioned place preference response and its subsequent recovery following extinction. MP2 completely blocks the formation of LTP in experiments on animal hippocampal slices during the conditioning stage corresponding to the acquisition of the morphine-induced conditioned place preference and the consolidation of addictive memory. The research was carried out within the state assignment of Ministry of Science and Higher Education of the Russian Federation for FRC FTM.