The sigma1 receptor agonist enhances long-term depression caused by activation of metabotropic glutamate receptors in rat hippocampal neurons

Introduction. Metabotropic glutamate receptors of group 1 (mGluR1/5) are an important component of the hippocampal inhibitory system. Disturbances of their work lead to manifestation of various pathologies of the nervous system. The search for effective ways of regulating the work of mGluR1/5 is an urgent problem of neuropharmacology. In the present study, we assessed for the first time the possibility of modulating mGluR1/5 by activation of sigma1 receptors (Sig1-R), chaperone proteins capable of directly to directly interact with other proteins and to enhance their activity.

Objective. To study the effect of a specific Sig1-R agonist, PRE-084, on long-term depression of glutamate inputs in the hippocampus caused by activation of mGluR1/5.

Materials and methods. On slices of the hippocampus of rat brain in the CA1 region, population spikes (PS) caused by stimulation of Shaffer collaterals were registered. Activation of mGluR1/5 was induced by the application of 50 μM of specific agonist of these receptors, dihydroxyphenylglycine (DHPG), for 10 min. Activation of Sig1-R was induced by the application of 10 μM of specific agonist PRE-084 for 20 min.

Results. A short-term incubation of a rat hippocampal slice in a solution containing DHPG, caused a long-term depression of PS, so that within 30 min after the slice was washed away from the preparation, its amplitude was 60.0±14.4% of the control value (n=5). In the second series of experiments DHPG was applied against the background of the agonist Sig1-R PRE-084. PRE-084 was found to cause an increase in the inhibitory aftereffect of DHPG, so that the amplitude of the PS measured after 30 min after removal of the preparations from the surrounding solution was 16.0±1.7% (р<0.05).

Conclusion. It was shown for the first time that activation of Sig1-R enhances the functional activity of mGluR1/5.