Development of synaptic onset latency and threshold in auditory cortex in rats / 中华耳鼻咽喉头颈外科杂志

ABSTRACT

<p><b>OBJECTIVE</b>To study the change of synaptic onset latency and threshold in primary auditory cortex (A1) during the development of SD rat.</p><p><b>METHODS</b>Extracellular recording was used to locate A1, followed by transferred to loose-patch and whole-cell patch in vivo to record the spike activity, synaptic onset latency and threshold responses respectively. Rats were divided into 4 groups according to ages, postnatal 12-15 days, 16-18 days, 19-24 days and adult (> 3 months).</p><p><b>RESULTS</b>1. The onset latency of local field potential in A1 of adult rats[(10-20)ms] was shorter than young rats[(20-30)ms]. 2. During development, the onset latency of spikes of a single neuron in response to white noise pulses decreased. And the latency in young rats P12-15 [(40.15 ± 2.67) ms] and P16-18 [(33.86 ± 4.61) ms] were longer than in adults [(22.93 ± 2.94) ms] (ANOVA-test, t = 4.330 and 1.995, P = 0.00 and 0.04) . However, the onset latencies of P19-24 [(24.80 ± 3.63) ms] and adult had no significant difference (P > 0.05). 3.Synaptic onset latencies of both excitation and inhibition were significantly longer in P12-15[ (38.94 ± 1.90) ms, (35.26 ± 2.40) ms] and P16-18[ (32.68 ± 2.52) ms, (30.24 ± 2.18) ms] than in adults [(19.4 ± 1.06) ms, (18.91 ± 0.77) ms] excitation (t = 6.255 and 4.662, P < 0.01) inhibition (t = 8.918 and 4.820, P < 0.01) showed significant difference. Whereas the onset latencies of P19-24[ (23.67 ± 2.46) ms, (21.43 ± 1.80) ms] and adults displayed no prominent difference(P > 0.01). Meanwhile, the difference between the onset latencies of excitation and inhibition became narrower during development[ (3.15 ± 1.02) ms, (2.01 ± 0.73) ms, (1.79 ± 0.85) ms, (0.39 ± 0.48) ms]. P12-15 had notably difference in comparison to adults (t = 1.739, P < 0.01). 4. The thresholds of synaptic response were notably higher in P12-15 (40.0 ± 1.6) dB and P16-18 (41.3 ± 11.6) dB when compared with adults (30.9 ± 0.6) dB (t = 5.284 and 5.867, P < 0.01) . While that of P19-24 (35.0 ± 32.7) dB showed no distinct difference (P > 0.01).</p><p><b>CONCLUSION</b>Single neuron spiking activity, synaptic onset latency and threshold evoked by sound stimulus gradually mature during the development in rat A1.</p>