Journal of Applied Physiology, Vol 59, Issue 5 1597-1600, Copyright © 1985 by American Physiological Society
Chemosensitivity of crayfish slowly adapting stretch receptors to nicotine
R. F. Taylor and D. T. Frazier
It has recently been demonstrated that slowly adapting stretch receptors
(SASRs) in the airways of the dog respond directly to nicotine (Federation
Proc. 43: 318, 1984). The purpose of the present experiment was to
investigate this chemical effect on an isolated stretch receptor. The
crayfish muscle receptor organ was chosen, since crayfish muscle is
reported to be insensitive to nicotine or acetylcholine and therefore
permits the testing of any direct chemical effect of nicotine on the muscle
stretch receptors. The tail was removed and pinned out in a tissue bath,
and a stretch receptor organ was surgically isolated. Single-unit SASR
extracellular nerve recordings were made while simultaneously measuring
tension in the tail. Drugs were prepared in Van Harreveld's solution and
administered into the bath kept at 18 degrees C. When resting muscle
tension was essentially reduced to zero by cutting both ends of the
receptor organ muscle, nicotine (0.07 microM) added to the bath increased
receptor activity fourfold. This response was abolished by treatment with
hexamethonium (690 microM). In a second group of animals in which the
muscle was left intact, nicotine was shown to significantly increase
receptor sensitivity to step changes in muscle tension. Once again
hexamethonium blocked the response to nicotine. These results demonstrate
that the sensitivity of mechanoreceptor can be altered by chemical
interaction with nicotinic receptors, which dramatically alter sensory
receptor activity.
