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Biol Bull 93: 72-88. (August 1947)
© 1947 Marine Biological Laboratory
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THE ACTION OF ELECTRICAL STIMULATION AND OF CERTAIN DRUGS ON CARDIAC NERVES OF THE CRAB, CANCER IRRORATUS

RALPH I. SMITH 1

1 The Biological Laboratories, Harvard University, Cambridge, Mass.

1. The heart of Cancer irroratus has been perfused in situ, the beat recorded mechanically, and the inhibitory and excitatory nerves stimulated while the heart was perfused with various drugs.

2. Nervous inhibition of the heart induced by stimulation of the inhibitory nerves is usually total with no inhibitory after-effect.

3. Nervous excitation of the heart induced by stimulation of the excitatory nerves frequently shows a stimulatory after-effect.

4. The cardio-inhibitory nerves appear to be more effective than the excitatory nerves, but each type of, nerve can modify to some extent the effectiveness of the other.

5. The excitatory nerves are effective when stimulated at frequencies ranging from 200-300 per second down to 10 per second or less.

6. The inhibitory nerves produce total inhibition when stimulated from 15-20 to 100-200 times per second. At frequencies extending above and below this range, partial inhibition may be obtained.

7. Strychnine, in concentrations of 1:2,500, blocks reversibly the action of both excitatory and inhibitory nerves.

8. Atropine is without effect upon excitatory and inhibitory nerves, as well as upon the heart ganglion in concentrations sufficient to abolish the action of applied acetylcholine.

9. Nicotine, in low concentrations, augments the effectiveness of the excitatory nerves as well as of the heart ganglion.

10. Nicotine in high concentrations may block the passage of impulses from cardiac ganglion to muscle; hence it could not be determined with certainty if nicotine blocks the excitatory nerves.

11. Neither eserine alone, nor with acetylcholine in stimulatory concentrations, augmented cardio-inhibition or excitation. It is suggested that the lack of effect of eserine upon the excitatory nerves deserves restudy.

12. It is probable that the excitatory nerves are cholinergic, and exert a somewhat "nicotine-like" effect upon the heart ganglion, which in turn exerts a "nicotine-like" action at the neuromuscular junction.

13. No light has been thrown on the pharmacological nature of the cardio-inhibitory nerves.




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I. M. Cooke
Reliable, Responsive Pacemaking and Pattern Generation With Minimal Cell Numbers: the Crustacean Cardiac Ganglion
Biol. Bull., April 1, 2002; 202(2): 108 - 136.
[Abstract] [Full Text] [PDF]


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