Activation of the heart normally begins in the sinoatrial node (SAN). Electrical impulses spontaneously released by SAN pacemaker cells (SANPCs) trigger the contraction of the heart. However, the cellular nature of SANPCs remains controversial. Here, we report that SANPCs exhibit glutamatergic neuron-like properties. By comparing the single-cell transcriptome of SANPCs with that of cells from primary visual cortex in mouse, we found that SANPCs co-clustered with cortical neurons. Tissue and cellular imaging confirmed that SANPCs contained key elements of glutamatergic neurotransmitter system, expressing genes encoding glutamate synthesis pathway (Gls), ionotropic and metabotropic glutamate receptors (Grina, Gria3, Grm1 and Grm5), and glutamate transporters (Slc17a7). SANPCs highly expressed cell markers of glutamatergic neurons (Snap25 and Slc17a7), whereas Gad1, a marker of GABAergic neurons, was negative. Functional studies revealed that inhibition of glutamate receptors or transporters reduced spontaneous pacing frequency of isolated SAN tissues and spontaneous Ca²⁺ transients frequency in single SANPC. Collectively, our work suggests that SANPCs share dominant biological properties with glutamatergic neurons, and the glutamatergic neurotransmitter system may act as an intrinsic regulation module of heart rhythm, which provides a potential intervention target for pacemaker cell-associated arrhythmias.

心脏的激活通常始于窦房结 (SAN)。SAN 起搏器细胞 (SANPC) 自发释放的电脉冲触发心脏收缩。然而，SANPCs 的细胞性质仍然存在争议。在这里，我们报告 SANPCs 表现出谷氨酸能神经元样特性。通过比较SANPCs的单细胞转录组与小鼠初级视觉皮层细胞的转录组，我们发现SANPCs与皮质神经元共聚集。组织和细胞成像证实 SANPCs 含有谷氨酸能神经递质系统的关键元件，表达编码谷氨酸合成途径 ( Gls )、离子型和代谢型谷氨酸受体 ( Grina、Gria3、Grm1和Grm5）和谷氨酸转运蛋白（Slc17a7）。SANPCs 高表达谷氨酸能神经元的细胞标志物（Snap25和Slc17a7），而GAD1是 GABA 能神经元的标志物，呈阴性。功能研究表明，谷氨酸受体或转运蛋白的抑制降低了分离的 SAN 组织的自发起搏频率和单个 SANPC 中自发的 Ca ²⁺瞬变频率。总的来说，我们的工作表明，SANPCs 与谷氨酸能神经元具有共同的主要生物学特性，谷氨酸能神经递质系统可能作为心律的内在调节模块，为起搏细胞相关的心律失常提供潜在的干预目标。