Abstract
The contractile activity of smooth muscle in the capsules of bovine tracheobronchial lymph nodes was recorded. On electrical stimulation with a field (impulse amplitude 55 V, duration 0.5 msec, frequency 0.5, 1, 2, 4, 8, 16, and 32 Hz), strips of lymph node capsule showed frequency-dependent increases in tone and phasic contraction frequency. Reactions evoked by electrical stimulation were significantly (by 80%) suppressed by tetrodotoxin (10–6 M). Blockade of M-cholinoreceptors with atropine did not lead to any change in the effects of stimulation. The contractile response of preparations to electrical stimulation on the background of phentolamine (10–7–10–6 M) were significantly suppressed but not completely prevented. Propranolol (10–7–10–6 M) did not alter or slightly increased the contractile responses of lymph node capsules to electrical stimulation. These data lead to the conclusion that the contractile activity of tracheobronchial lymph node capsule smooth muscle is modulated (at least partially) by excitatory noradrenergic nerve fibers.
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