Abstract: | At present, there are no direct methods to determine the number of synaptic receptor-related channels activated in the course
of synaptic transmission (N) or a value of the single-channel conductance (γ). Peak-scaled nonstationary fluctuation analysis (PS NSFA) should be considered
the most well-developed indirect approach used for estimating these parameters. Despite the relatively wide using of this
approach for the analysis of various synaptic currents, some aspects of possible errors that can occur in the course of data
acquisition or their subsequent processing have not been studied. We examined in detail the problem of applicability of PS
NSFA in the study of spontaneous and evoked GABA-ergic inhibitory postsynaptic currents (IPSCs). IPSCs were recorded using
a dual patch-clamp technique from hippocampal neurons growing in low-density cultures. Parameters of the recorded IPSCs and
values for different components of GABA-ergic synaptic transmission reported earlier were used for simulations and PS-NSFA
analysis. In Monte Carlo computer simulations of evoked IPSCs, the influence of series resistance, background noise, asynchronicity
of transmitter release, GABAA channel properties, dendritic attenuation, and instrumental filtering on γ estimates obtained by PS NSFA was examined. We
concluded that the γ and, consequently, N values may be satisfactorily estimated by the suggested approach using spontaneous and evoked IPSCs recorded in inhibitory
synaptic connections in hippocampal cultures within a wide range of experimental conditions. We also estimated the mean of
the single-channel conductance of synaptic GABAA receptors in neurons from primary hippocampal cultures and found that this value (29 ± 5 pS) agrees well with the high conductance
of single synaptic GABAA receptors observed in acute hippocampal slices. This indicates that dissociated cultures are an adequate model for studying
the properties of synaptic GABAA receptors.
Neirofiziologiya/Neurophysiology, Vol. 37, No. 4, pp. 379–388, July–August, 2004. |