Jc. Jorgerivera et E. Marder, TNRNFLRFAMIDE AND SDRNFLRFAMIDE MODULATE MUSCLES OF THE STOMATOGASTRIC SYSTEM OF THE CRAB CANCER-BOREALIS, Journal of comparative physiology. A, Sensory, neural, and behavioral physiology, 179(6), 1996, pp. 741-751
The effects of the extended FLRF amide-like peptides, TNRNFLRFamide an
d SDRNFLRFamide, were studied on the stomach musculature of the crab C
ancel borealis. Peptide-induced modulation of nerve-evoked contraction
s was used to screen muscles. All but 2 of the 17 muscles tested were
modulated by the peptides. In several muscles of the pyloric region, p
eptides induced long-lasting myogenic activity. In other muscles, the
peptides increased the amplitude of nerve-evoked contractions, excitat
ory junctional potentials, and excitatory junctional currents, but pro
duced no apparent change in the input resistance of the muscle fibers.
The threshold concentration was 10(-10) M for TNRNFLRFamide and betwe
en 10(-9) M to 10(-8) M for SDRNFLRFamide. The absence of direct pepti
de-containing innervation to these muscles and the wide-spread sensiti
vity of these muscles to the peptides suggest that TNRNFLRFamide and S
DRNFLRFamide may be released from neurosecretory structures to modulat
e stomatogastric musculature hormonally. We speculate that hormonally
released peptide will be crucial for maintaining appreciable muscle co
ntraction in response to low-frequency and low-intensity motor dischar
ge.