Ermirio R, Ruggeri P, Cogo C E, Molinari C, Calaresu F R
Istituto di Fisiologia Umana, Facoltà di Medicina e Chirurgia, Università di Genova, Italy.
Am J Physiol. 1991 Jun;260(6 Pt 2):R1089-94. doi: 10.1152/ajpregu.1991.260.6.R1089.
Effects of microinjection of atrial natriuretic factor (ANF) into cardioinhibitory sites in the nucleus ambiguous (NA) or on single vagal cardioinhibitory neurons (VCN) were investigated in urethan-anesthetized rats. Sites containing cardioinhibitory neurons were identified by observing a marked and reproducible bradycardia in response to microiontophoretically applied (20-40 nA) or microinjected (20 nl) 0.1 M L-glutamate. In 35 of the 40 (87.5%) cardioinhibitory sites identified by microinjection of glutamate, ANF (20 nl of 10(-7) M) decreased heart rate (HR; -47.1 +/- 2.5 beats/min). No responses were elicited in the other five sites. In animals paralyzed and artificially ventilated, the HR effects of ANF were not significantly different before and after muscle paralysis. Microinjections of 10 nl of 10(-7) M ANF caused excitation of 19 of 21 VCN (90%), which was followed by a decrease in HR (-20.8 +/- 2.3 beats/min); no neuronal or cardiovascular responses were elicited by ANF in the remaining two VCN. Bilateral vagotomy or atropine sulfate (1 mg/kg iv) abolished cardiac slowing without affecting neuronal activation, whereas propranolol (2 mg/kg iv) did not affect either response to ANF. These results suggest that ANF is a neuromediator involved in the excitation of cardioinhibitory neurons in the NA.
在乌拉坦麻醉的大鼠中，研究了向疑核（NA）的心抑制位点或单个迷走神经心抑制神经元（VCN）微量注射心房利钠因子（ANF）的作用。通过观察对微量离子导入法施加（20 - 40 nA）或微量注射（20 nl）0.1 M L-谷氨酸产生的明显且可重复的心动过缓，来确定含有心抑制神经元的位点。在通过微量注射谷氨酸确定的40个心抑制位点中的35个（87.5%），ANF（10⁻⁷ M的20 nl）可使心率（HR）降低（-47.1 ± 2.5次/分钟）。在其他五个位点未引发反应。在瘫痪并进行人工通气的动物中，肌肉瘫痪前后ANF对HR的影响无显著差异。微量注射10 nl的10⁻⁷ M ANF可使21个VCN中的19个（90%）兴奋，随后HR降低（-20.8 ± 2.3次/分钟）；在其余两个VCN中，ANF未引发神经元或心血管反应。双侧迷走神经切断术或硫酸阿托品（1 mg/kg静脉注射）可消除心脏减慢，但不影响神经元激活，而普萘洛尔（2 mg/kg静脉注射）对ANF的任何一种反应均无影响。这些结果表明，ANF是一种参与NA中心抑制神经元兴奋的神经介质。
