Evoked inhibitory postsynaptic currents in the dynamics of development of cultured hippocampal neurons of rats

On a low-density culture of the hippocampal neurons of rats, we studied inhibitory transmission through the synaptic connection of a cell pair; a patch-clamp technique in the whole-cell configuration and direct exetracellular stimulation of the neurites were used. We found that the mean amplitude of evoked inhibitory postsynaptic currents (eIPSC) and variability of their amplitudes signficantly increased within the culturing period. The duration of the current rising phase also increased concurrently with the growth and differentiation of the neurons, but this chang was non-monotonic. The coefficient of variation of the current amplitudes, as well as the time constant of current decay (the latter reflects the properties of a postsynaptic unit), showed no clear changes in the course of culturing of the neurons. Our data show that in the course of synaptogenesis the number of unitary inhibitory synaptic contacts between cultured hippocampal neurons increases, while modifications of the transmission mechanism a the level of unitary synaptic contact are less significant.