BDNF (Brain-Derived Neurotrophic Factor) Mediated Presynaptic Neuronal Signal from the Inhibitory Setting of Cortical Pyramidal Neurons Recorded from Brain Slices

BDNF (brain-derived neurotrophic factor) has a tremendous effect on GABAergic synaptic transmission in the developing and adult central nervous system. Paired pulse stimuli are the common way to observe the paired-pulse ratio (PPR) that is the indicator of presynaptic transmission. During paired-pulse stimuli, the second response might be larger or smaller than the first one. To investigate BDFN induced presynaptic signal in the inhibitory neuron of the visual cortex, we used whole-cell patch-clamp recordings from the pyramidal neurons of mice visual cortex and studied signals evoked by paired-pulse stimuli. A total of seven mice brain slices were prepared for this study. AP5 and NBQX were added in artificial cerebrospinal fluid (aCSF) to block NMDA and non-NMDA receptors, respectively. Three levels of BDNF concentrations were used to see the effect of BDNF on GABAergic synaptic release; 0 ng/ml, 20 ng/ml, and 100 ng/ml of BDNF concentrations. Inhibitory postsynaptic currents as IPSC1 and IPSC2 were recorded after paired-pulse stimuli in the pyramidal neurons during all three conditions. PPR was measured as IPSC2/IPSC1. PPRs were compared among groups to see the significant differences. There were no significant differences between 0 ng/ml vs 20 ng/ml, 0 ng/ml vs 100 ng/ml and 20 ng/ml vs 100 ng/ml of BDNF concentrations. However, there was a tendency of reducing PPR during 20 & 100 ng/ml of BDNF concentration compare to 0 ng/ml might indicate diminished presynaptic transmitter releases. These results may suggest that BDNF has no activity-independent effect on the PPR of transmitter release at visual cortical inhibitory synapses.