The purpose of this research was determine whether the tachycardia from naloxone-precipitated withdrawal from opiates w vagally mediated. Our previous results with many drugs of abuse led to the hypothesis that naloxone-precipitated withdrawal, unlike the abused drugs that we have studied, produces sympathetically mediated tachycardia. The subjects were 19 individuals, male and female, who were dependent on opiates at the time of testing. We recorded heart rate continuously before and after the injection of naloxone (1 mg). The results indicated that the tachycardia from naloxone-precipitated withdrawal was substantial. These increases in heart rate were mirrored precisely by increases in the 0.10 Hz. rhythm. There was no change in vagal tone index. This pattern of response was consistent with sympathetic mediation of the effect on heart rate. The results with this drug, which is dysphoragenic, stand in marked contrast to our results with drugs of abuse.
