Journal of Neurophysiology, Vol 63, Issue 6 1426-1435, Copyright © 1990 by APS

ARTICLES

Regulation of heartbeat in Lymnaea by motoneurons containing FMRFamide-like peptides

K. J. Buckett, M. Peters, G. J. Dockray, J. Van Minnen and P. R. Benjamin
MRC Neurophysiology Research Group, School of Biological Sciences, University of Sussex, Falmer, Brighton, United Kingdom.

1. Intracellular stimulation of single neurons in the Lymnaea CNS was carried out to identify heart motoneurons. 2. Two of the identified motoneurons, the E heart excitor (Ehe) cells, were shown to contain Phe-Met-Arg-Phe-NH2 (FMRFamide)-like peptides by immunocytochemical staining of dye-marked neurons and by radioimmunoassay (RIA) applied to extracts of single dissected cells. 3. Bursts of spikes in the Ehe cells increased heart rate, beat amplitude and muscle tonus. This response was mimicked by perfusion of exogenous FMRFamide at low concentration (10(-6) to 5 x 10(-8) M) through the interior of the intact heart. 4. Application of selective antagonists to 5-hydroxytryptamine (5-HT) and dopamine failed to block Ehe cardiac effects. 5. Detailed evidence that the Ehe cells were heart motoneurons was obtained. 1) Anatomic mapping using the dye Lucifer yellow showed Ehe cells had peripheral projections restricted mainly to the intestinal nerve, the only nerve known to innervate the heart. 2) Perfusion of the CNS with a saline containing Co2+ blocked central chemical synapses but did not affect activity of Ehe cells on the heart. 3) Simultaneous intracellular recordings from Ehe cells and auricle muscle fibers showed unitary excitatory junction potentials following with constant latency from spikes in Ehe cells. 6. The present study elucidates the role of FMRFamide in cardioregulation and provides the first evidence that it acts as an excitatory neurotransmitter on the snail heart.

This article has been cited by other articles:

				C. R. Jimenez, S. Spijker, S. de Schipper, J. C. Lodder, C. K. Janse, W. P. M. Geraerts, J. van Minnen, N. I. Syed, A. L. Burlingame, A. B. Smit, et al. Peptidomics of a Single Identified Neuron Reveals Diversity of Multiple Neuropeptides with Convergent Actions on Cellular Excitability J. Neurosci., January 11, 2006; 26(2): 518 - 529. [Abstract] [Full Text] [PDF]

				S. J. Perry, V. A. Straub, M. G. Schofield, J. F. Burke, and P. R. Benjamin Neuronal Expression of an FMRFamide-Gated Na+ Channel and Its Modulation by Acid pH J. Neurosci., August 1, 2001; 21(15): 5559 - 5567. [Abstract] [Full Text] [PDF]

				M. S. Yeoman and P. R. Benjamin Two Types of Voltage-Gated K+ Currents in Dissociated Heart Ventricular Muscle Cells of the Snail Lymnaea stagnalis J Neurophysiol, November 1, 1999; 82(5): 2415 - 2427. [Abstract] [Full Text] [PDF]

				B. L. Brezden, M. S. Yeoman, D. R. Gardner, and P. R. Benjamin FMRFamide-Activated Ca2+ Channels in Lymnaea Heart Cells Are Modulated by "SEEPLY," a Neuropeptide Encoded on the Same Gene J Neurophysiol, April 1, 1999; 81(4): 1818 - 1826. [Abstract] [Full Text] [PDF]

				D Willoughby, M. Yeoman, and P. Benjamin Inositol-1,4,5-trisphosphate and inositol-1,3,4,5-tetrakisphosphate are second messenger targets for cardioactive neuropeptides encoded on the FMRFamide gene J. Exp. Biol., January 10, 1999; 202(19): 2581 - 2593. [Abstract] [PDF]

				C. P. Tensen, K. J. A. Cox, A. B. Smit, R. C. van der Schors, W. Meyerhof, D. Richter, R. J. Planta, P. M. Hermann, J. van Minnen, W. P. M. Geraerts, et al. The Lymnaea Cardioexcitatory Peptide (LyCEP) Receptor: A G-Protein-Coupled Receptor for a Novel Member of the RFamide Neuropeptide Family J. Neurosci., December 1, 1998; 18(23): 9812 - 9821. [Abstract] [Full Text] [PDF]