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Biol Bull 118: 111-119. (February 1960)
© 1960 Marine Biological Laboratory
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THE RELEASE OF EFFERENT NERVE ACTIVITY IN THE ROACH, PERIPLANETA AMERICANA, BY EXTRACTS OF THE CORPUS CARDIACUM

NANCY MILBURN 1, ELIZABETH A. WEIANT 1, and KENNETH D. ROEDER 1

1 Department of Biology, Tufts University, Medford 55, Massachusetts

1. Increased activity and regular bursts of efferent nerve spikes are seen on nerves IX and X from the cercal ganglion of roaches when extracts of corpora cardiaca are applied to the exposed abdominal cord or injected into the head capsule. Such motor nerve activity is usually inhibited in the intact animal by the presence of some influence arising in the subesophageal ganglion (Roeder, Tozian and Weiant, 1960). The corpus cardiacum extracts appear to suppress the action of this inhibitory center. The threshold concentration for this effect is approximately one pair of corpora cardiaca per 0.01 ml. of saline when the extract is applied to the abdominal cord, or three pairs injected into the head in about 0.01 to 0.02 ml. of saline. In decapitated male mantids a similar type of nerve fiber activity is believed to result in behavior associated with mating.

2. The corpus cardiacum extracts seem temporarily to increase the activity of the abdominal nerve cord in preparations with an intact central nervous system. When high concentrations of extract are used, the cord activity is occasionally depressed or blocked. The effects of the extract are only partially reversible by washing the preparation with saline.

3. The activity of certain efferent fibers in the thoracic region is similarly affected by corpus cardiacum extract, the action mimicking that produced by decapitation or cord transection.

4. Corpus cardiacum extracts have no significant effects on the transmission of impulses at the synapse between the cercal nerve and the giant fibers in an electrically stimulated preparation.

5. The DDT-toxin of Sternberg does not have the same effect on the roach nervous system as the active principle in extracts of corpora cardiaca.

6. The corpus cardiacum extracts may be preserved successfully by quick-freezing. Their activity is decreased by prolonged heating, but warming for five minutes at 90° to 100° C. leaves the potency unaffected. Such warming seems to increase by several hours the length of time that an extract will remain potent.




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