When the heart inhibits the brain: cardiac phases modulate Short-interval intracortical inhibition

Background: The phasic cardiovascular activity influences the central nervous system through the systolic baroreceptor inputs, inducing widespread inhibitory effects on behaviour. Despite this, few studies assessed how the cardiac systole affects neurotransmission within our nervous system. Hypothesis: Phasic systolic baroreceptor inputs affect the motor system through intracortical-inhibition modulation, in particular of fast-acting inhibitory postsynaptic potentials GABAA neurotransmission. Methods: Through Transcranial magnetic stimulation (TMS) delivered during resting-state over the left primary motor cortex and across the different cardiac phases, we measured corticospinal excitability-(CSE) and distinct indices of intracortical motor inhibition: short-(SICI) and long-(LICI) interval, corresponding to GABAA and GABAB neurotransmission, respectively. Results: We found a significant interaction between the cardiac phase and intracortical inhibition specific for SICI only. SICI was stronger at systole than at diastole. Conclusions: These results show a tight relationship between the cardiac cycle and the inhibitory neurotransmission within M1, and in particular with GABAA–ergic mediated motor inhibition.

研究背景：阶段性心血管活动可通过收缩期压力感受器传入信号作用于中枢神经系统，对行为产生广泛的抑制效应。然而目前鲜有研究探讨心脏收缩期如何影响神经系统内的神经传递过程。
研究假说：阶段性收缩期压力感受器传入信号通过调控皮层内抑制，尤其是γ-氨基丁酸A型（GABAA）介导的快速作用抑制性突触后电位神经传递，来影响运动系统。
研究方法：本研究通过在静息状态下对左侧初级运动皮层施加经颅磁刺激（Transcranial magnetic stimulation, TMS），并覆盖不同心脏时相，以此测量皮质脊髓兴奋性（CSE）以及皮层内运动抑制的两类核心指标：短间隔皮层内抑制（SICI）与长间隔皮层内抑制（LICI），二者分别对应GABAA与GABAB型神经传递。
研究结果：我们发现心脏时相与皮层内抑制之间存在显著交互作用，且该交互作用仅特异性见于短间隔皮层内抑制（SICI）。SICI在心脏收缩期的强度显著高于舒张期。
研究结论：上述结果表明，心脏周期与初级运动皮层（M1）内的抑制性神经传递存在紧密关联，尤其与GABAA能介导的运动抑制密切相关。