Journal of Applied Physiology, Vol 43, Issue 6 1039-1045, Copyright © 1977 by American Physiological Society
Role of autonomic nervous system controlling surface tension in fetal rabbit lungs
A. J. Corbet, P. Flax and A. J. Rudolph
After the maternal abdomen was opened under methoxyflurane anesthesia,
fetal rabbits of 27.5 days gestation were given injections through the
intact uterine wall of saline, pilocarpine, isoxsuprine, muscarine,
phenylephrine, atropine, phenoxybenzamine, or propranolo, alone or in
appropriate combinations. Fetal rabbits were delivered by hysterotomy and
killed without breathing 2.5 h later. Static pressure-volume curves with
air showed improved retention on deflation in fetal rabbits that had
injections of pilocarpine, or isoxsuprine, but not of muscarine or
phenylephrine. The effect of pilocarpine on the pressure-volume curve was
blocked by atropine, phenoxybenzamine, and propranolol, and the effect of
isoxsuprine was blocked by propranolol but not phenoxybenzamine. The data
suggest that pilocarpine produces secretion of surfactant into lung air
spaces by exciting the sympathetic nervous system, a known function of
pilocarpine, rather than the parasympathetic nervous system. This may
result in stimulation of the same beta-adrenergic receptors affected by
isoxsuprine which is also thought to stimulate surfactant secretion.
