A comparison of the effects of pancuronium bromide and its monoquaternary analogue, ORG NC 45, on autonomic and somatic neurotransmission in the rat.

1 Potentiation by pancuronium of the effects of adrenergic nerve stimulation, previously shown in cardiovascular tissues, was also found in rat anococcygeus and vas deferens, in vitro or in vivo. 2 In the pithed rat, in the presence of pancuronium, pre-junctional alpha-adrenoceptor-mediated feedback inhibition of cardiac sympathetic transmission was uncovered at relatively low stimulation frequencies by phentolamine or yohimbine. 3 The effects of pancuronium and its mono-quaternary analogue Org NC 45 on autonomic and somatic neuromuscular transmission were compared, in the pithed rat. Org NC 45 was less potent than pancuronium at blocking somatic neuromuscular transmission by a factor of 2.1, at blocking cardiac, parasympathetic transmission by a factor of 538 and at potentiating sympathetic transmission by a factor of 33.

Organ-specificity of placebo effects on blood pressure.

There is increasing evidence that verbal suggestions accompanying placebo interventions can alter autonomic functions. The underlying mechanisms of these changes are not well understood. However, previous studies point at the specificity of such effects. The aim of the experiment was to lower blood pressure by a placebo intervention and to investigate the specificity of autonomic changes. Forty-five healthy participants received a single administration of an active drug (a homeopathic remedy), an identically-looking placebo drug, or no drug. Active drugs and placebo drugs were administered in a double-blind design and were accompanied by verbal suggestions of a blood-pressure lowering effect. Systolic and diastolic blood pressure, the electrocardiogram, electrodermal activity, and the electrogastrogram were recorded during 30min before and after the intervention, and changes in situational anxiety were assessed. Results indicated a decrease of systolic blood pressure in the placebo group, as compared to the control group. Diastolic blood pressure levels, heart rate, respiratory sinus arrhythmia, skin conductance, gastric slow-wave frequency and situational anxiety did not change differentially between groups. In conclusion, the reduction in systolic blood pressure following the placebo intervention could not be attributed to stress relief or anxiety reduction. Rather, results suggest that the placebo intervention specifically reduced systolic blood pressure.

Neuromuscular blocking and autonomic effects of vecuronium and atracurium in the anaesthetized cat.

The effects of vecuronium and atracurium on neuromuscular transmission, on the responses of the heart rate to vagal stimulation and on the responses to preganglionic stimulation of the nictitating membrane were compared in the chloralose-anaesthetized cat. Vecuronium was four times more potent than atracurium as a neuromuscular blocking agent, whereas the two compounds had similar potencies in blocking the effects of stimulation of the cardiac vagus. The vagal/neuromuscular ratios measured at 50% inhibition were 96 for vecuronium and 25 for atracurium. Vecuronium possessed a slightly shorter recovery time than atracurium and shorter duration of action on the soleus muscle. The onset times of the two compounds were not significantly different. Both compounds had longer time-courses of action than suxamethonium. Very large doses of vecuronium decreased the responses of the preganglionic stimulation of the nictitating membrane, suggesting that at high doses the compound possesses ganglion blocking activity. Large doses of atracurium also decrease the nictitating membrane responses and, in some cats, contractions of the nictitating membrane associated with increases in heart rate and arterial pressure were observed.