Electrophysiological Characteristics In HVC-RA Synapse Of Zebra Finches (Taeniopygia Guttata) And Comparison The Effect Of Different Stimulus Patterns

In this paper, we study for the first time theelectrophysiological characteristics in HVC-RA Synapse of the zebra finches in vivo and comparison the effect of different stimulus patterns .A stimulating electrode was placed in HVC nucleus and a glass micropipettes was inserted into RA sub-field to record maximal field potentials. We used Paired-pulse technique as test stimulation to study the paired pulses efficacy and compare the effect of different stimulus patterns including lHz, 5Hz, 50Hz, lOOHz and electrical theta-burst on the HVC-RA synaptic transmission. The results showed as follows:1. At HVC-RA synapse, we recorded evoked potentials of which PS, slope and area increased in a certain extent, but latency and duration (50% of peak) were stable with the stimulus intensity increasing. The input/output characters of evoked potential showed the change of the evoked potentials with stimulus intensity was conformed to the principle of electrics.2. Used 1/3,1/2,2/3,3/4,and the maximal of the value that induced the largest response of synapses as test stimulus intensity, paired-pulse stimulation with intervals of 50-ms, 75-ms 100-ms showed latency and duration (50% of peak) almost unchanged, but PS, slope and area produced paired-pulse facilitation (PPF) significantly.3. The PPF of the PS, slope and area decreased with the increasing of the interval of the paired-pulses all of which reached the maximal at the interval of 50-ms. The PPF of area was higher than the PPF of the other two, but there were no remarkable difference between them.4. Used 1/3,1/2,2/3,3/4,and the maximal of the value that induced the largest response of synapses as test stimulus intensity, we found that the PPF of the PS , slope and areaall decreased with the increasing of stimulus intensity.5. Some change of the evoked potential weren't observed by LFS of lHz with 20 pulses. But LFS of 5Hz with 20 pulses depressed the evoked potential significantly which returned to the baseline within 2-8 minutes. PS , slope and area showed the same changes .6. Most of the electrical theta-burst stimulation depressed the synaptic transmission efficiency significantly .The slope and area returned to the baseline within 10 minutes, But what interesting was the PS showed significantly potentiation right after depression (33.3% of all test).7. HFS (50Hz and lOOHz, 20 or 100 pulses) induced just a short-time depression which returned to baseline within 30 minutes, no matter how to increase stimulus frequency and stimulus time. PS, slope and area had the same changes.In conclusion, there was significantly paired pulse facilitation in HVC-RA synapse which decreased with the increasing of paired-pulses interval and test stimulus intensity. Both HFS and some of LFS depressed synaptic transmission for a short time.