Effects of nicotine on heart rate studied by direct perfusion of sinus code

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Abstract
In 26 dogs after pentobarbital anesthesia, the heart was exposed and the sinus node artery cannulated. Nicotine base solutions were injected into the sinus node in concentrations ranging from 0.01 to 100 [mu]g/ml. No systemic effects were obtained from concentrations below 100 [mu]g/ml. With 1.0 and 10 [mu]g/ml, both slowing and acceleration of the heart were observed. The slowing was abolished by intrandal atropine and the accleration by intranodal propranolol and intranodal hexamethonium. Nicotine also inhibited the effect of electrical stimulation of the cervical vagus nerve without modifying the response to intranodally injected acetylcholine. The heart rate response to stellate ganglion stimulation was not abolished by nicotine.