Priola D V, Cao X, Smith D C
Department of Physiology, University of New Mexico School of Medicine, Albuquerque 87131.
Am J Physiol. 1994 Apr;266(4 Pt 2):H1401-7. doi: 10.1152/ajpheart.1994.266.4.H1401.
The experiments were performed to determine whether the neuromodulatory effect of substance P (SP) could be demonstrated in the isolated atrium. Strips from the right (RA) and left atria (LA) of normal (control) and denervated canine hearts were placed in an isolated muscle bath, and isometric muscle tension was measured. Inotropic responses to direct muscarinic stimulation were obtained with 1 x 10(-9) to 1 x 10(-8) M acetylcholine (ACh), and responses to stimulation of the intramyocardial intrinsic cardiac nerves (ICN) were produced with nicotine (Nic), 1.0-10 x 10(-6) M. The same drugs were tested in the presence of 1 x 10(-6) M SP, which had no significant inotropic effects of its own. Responses to ACh were unaffected by SP. The primary negative inotropic response to Nic was greatly attenuated by SP in both control and denervated atria, whereas the secondary positive response in control atria was unaffected. This inhibition was very pronounced in LA but less so in the RA. We conclude that SP appears to modulate the responses of the ICN to nicotinic stimulation in a manner similar to that previously observed in intact animals. This mechanism may provide a means of direct modification of efferent cardiac responses by afferent nerves within the heart itself.
进行这些实验是为了确定在离体心房中是否能证实P物质（SP）的神经调节作用。将正常（对照）和去神经犬心脏的右心房（RA）和左心房（LA）的肌条置于离体肌肉浴中，并测量等长肌肉张力。用1×10⁻⁹至1×10⁻⁸M乙酰胆碱（ACh）获得对直接毒蕈碱刺激的变力反应，用1.0 - 10×10⁻⁶M尼古丁（Nic）刺激心肌内固有心脏神经（ICN）产生反应。在存在1×10⁻⁶M SP的情况下测试相同的药物，SP本身没有显著的变力作用。对ACh的反应不受SP影响。在对照和去神经的心房中，SP都极大地减弱了对Nic的主要负性变力反应，而对照心房中的次要正性反应不受影响。这种抑制在LA中非常明显，但在RA中则较弱。我们得出结论，SP似乎以类似于先前在完整动物中观察到的方式调节ICN对烟碱刺激的反应。这种机制可能提供了一种由心脏自身内的传入神经直接改变传出心脏反应的方式。
