Journal of Neurophysiology, Vol 61, Issue 5 1053-1063, Copyright © 1989 by APS

ARTICLES

Innervation of vascular and cardiac muscle of Aplysia by multimodal motoneuron L7

A. Alevizos, C. H. Bailey, M. Chen and J. Koester
Department of Psychiatry, Columbia University College of Physicians and Surgeons, New York, New York.

1. The cardiovascular system of Aplysia has proven to be a useful preparation for study of the neural control of circulation. To better understand the neural integration of function in this system, we have attempted to gain a more complete picture of its morphology and innervation patterns, with particular emphasis on the abdominal aorta and heart. 2. The vasoconstrictor muscle fibers of the abdominal aorta were found by dye injection to be extensively branched, with many processes that are less than 1 micron in diameter. Because of the wide spacing between individual muscle fibers, these fine processes, which have relatively few contractile filaments, may be required to mediate the electrical coupling that is observed between muscle cells. 3. L7, an identified cell in the abdominal ganglion, had been shown by others to be an excitatory motoneuron for the gill, the siphon, and the sheath-contracting muscles of the pleuroabdominal connectives, and also to excite the gill motoneurons in the branchial ganglion (5, 43, 56). We have found that this multimodal motoneuron also directly excites the auricle of the heart and the vasoconstrictor muscle of the abdominal aorta. 4. The excitatory effect of L7 on the abdominal aorta interacts synergistically with that produced by the other known excitatory inputs to that structure, the LBVc vasoconstrictor motoneurons. 5. The abdominal aorta is also richly innervated by axons immunoreactive for serotonin and for the neuropeptide FMRFamide. Serotonin inhibits the contractions of the aorta elicited by firing either L7 or the LBVC cells. In contrast, FMRFamide selectively inhibits the contractions elicited by the LBVC cells. 6. Our results suggest that a significant amount of the functional integration of the cardiovascular and respiratory systems is achieved by the use of a motoneuron common to both systems, and that there is likely to be extensive peripheral inhibitory modulation of the vasoconstrictor inputs to the abdominal aorta.

This article has been cited by other articles:

				K. Sasaki, F. Morishita, and Y. Furukawa Peptidergic innervation of the vasoconstrictor muscle of the abdominal aorta in Aplysia kurodai J. Exp. Biol., December 1, 2004; 207(25): 4439 - 4450. [Abstract] [Full Text] [PDF]

				S. Marinesco, K. E. Kolkman, and T. J. Carew Serotonergic Modulation in Aplysia. I. Distributed Serotonergic Network Persistently Activated by Sensitizing Stimuli J Neurophysiol, October 1, 2004; 92(4): 2468 - 2486. [Abstract] [Full Text] [PDF]

				C. Keating and P. E. Lloyd Differential Modulation of Motor Neurons That Innervate the Same Muscle but Use Different Excitatory Transmitters in Aplysia J Neurophysiol, October 1, 1999; 82(4): 1759 - 1767. [Abstract] [Full Text] [PDF]

				J. Levenson, J. H. Byrne, and A. Eskin Levels of Serotonin in the Hemolymph of Aplysia Are Modulated by Light/Dark Cycles and Sensitization Training J. Neurosci., September 15, 1999; 19(18): 8094 - 8103. [Abstract] [Full Text] [PDF]