Abstract:

Objective To investigate the dynamic changes of intrinsic properties and encoding at cortical GABAergic neurons with increase of depolarizing stimulus intensity in mice. Methods FVB-Tg (Gad GFP) 45704 Swn/J mice aged 15 to 22 d were sacrificed, and the cortical slices were obtained and cultured in vitro. The intrinsic properties and encoding parameters were recorded by using Axoclamp-2B amplifier. The changes of inter-spike intervals (ISI) and standard deviation of spike timing (SDST), as well as absolute refractory period (ARP) at cortical GABAergic neurons with increase of depolarizing stimulus intensity (threshold stimulus intensity ×0.7 group, ×0.85 group, ×1 group and ×1.25 group respectively) in mice were observed, and the association of ARP at cortical GABAergic neurons with ISI and SDST was analysed. Results With the increase of depolarizing stimulus intensity, the spike capacity of cortical GABAergic neurons was significantly increased, and ARP, ISI and SDST were significantly decreased (P<0.01) There was linear correlation between ARP and ISI in threshold stimulus intensity ×0.7 group, ×0.85 group, ×1 group and ×1.25 group (r²=0.9, 0.91, 0.82 and 0.84 respectively, P<0.05 for all), and there was also linear correlation between ARP and SDST in these groups (r²=0.97, 0.98, 0.93 and 0.89 respectively, P<0.05 for all). Conclusion With the increase of depolarizing stimulus intensity, the reduction of ARP at cortical GABAergic neurons improves spike capacity and capability of neural coding, which in turn enhances their ability in stabilizing the excitatory state of cerebral cortex.

Key words: cerebral cortex, GABAergic neuron, depolarizing stimulus, neural coding, mice