The cardio-regulator nerves of hermit crabs: Multimodal activation of the heart by the accelerator axons
- 24 Downloads
Some branches of the cardio-accelerator axons run directly to peripheral ganglionic tissue in the hermit crabs (Aniculus aniculus andDardanus crassimanus). Effects of the branches on cardiac tissues were studied electrophysiologically in a preparation in which the main trunk had been severed.
The branches of the cardio-accelerator axons exerted their acceleratory effects directly on two different tissues, peripheral motor processes of the ganglion and the myocardium.
Stimuli applied to the cardio-accelerator axons elicited impulses in ganglionic motor axons at terminal processes, but not in a one-to-one manner. For each ganglionic axon impulse an EJP was recorded from the myocardium. Therefore, the EJPs were identified as intrinsic EJPs due to activation of ganglionic axons by cardio-accelerator axons.
Small depolarizing potentials recorded from the myocardium corresponded one-to-one to stimuli applied to the cardio-accelerator axons. The following results show that the small potentials were EJPs: (i) The potentials showed summation and facilitation. (ii) Amplitude of the potentials varied depending on the level of the membrane potential. (iii) Amplitude of the potentials increased in a high Ca2+, low Mg2+ saline and decreased in a Ca2+-free, high Mg2+ saline. The EJPs were identified as extrinsic EJPs evoked directly in a muscle cell innervated by the accelerator axons.
The cardio-accelerator nerves excite the heart by multimodal activation, i.e. directly on the main trunk of the cardiac ganglion, on peripheral motor processes of the ganglion, and on the myocardium.
KeywordsMuscle Cell Membrane Potential Cardiac Tissue Motor Process Hermit Crab
dorsal cardiac nerve
Unable to display preview. Download preview PDF.
- Alexandrowicz JS (1932) The innervation of the heart of the Crustacea. I. Decapoda. Q J Microsc Sci 75:181–249Google Scholar
- Anderson M, Cooke IM (1971) Neural activation of the heart of the lobsterHomarus americanus. J Exp Biol 55:449–468Google Scholar
- Benson JA (1981) Synaptic and regenerative responses of cardiac muscle fibers in the crab,Portunus sanguinolentus. J Comp Physiol 143:349–356Google Scholar
- Brown HF (1964) Electrophysiological investigations of the heart ofSquilla mantis. II. The heart muscle. J Exp Biol 41:701–722Google Scholar
- Delaleu JC, Holley A (1976) Neural regulation of the heart muscle in an isopod crustacean: acceleration and peripheral inhibition. J Exp Biol 64:345–356Google Scholar
- Florey E (1960) Studies on the nervous regulation of the heart beat in decapod Crustacea. J Gen Physiol 43:1061–1081Google Scholar
- Hallett M (1971) Lobster heart: electrophysiology of single cells including effects of the regulator nerves. Comp Biochem Physiol 39A:643–648Google Scholar
- Holley A, Delaleu JC (1972) Electrophysiology of the heart of an isopod crustacean:Porcellio dilatatus. I. General properties. J Exp Biol 57:589–608Google Scholar
- Kihara A, Kuwasawa K (1984) Neuroanatomical and electrophysiological analysis of the nervous regulation in the heart of the isopod crustacean,Bathynomus doederleini. J Comp Physiol A 154:883–894Google Scholar
- Kuramoto T, Kuwasawa K (1980) Ganglionic activation of the myocardium of the lobster,Panulirus japonicus. J Comp Physiol 139:67–76Google Scholar
- Maynard DM (1953) Activity in a crustacean ganglion. I. Cardio-inhibition and acceleration inPanulirus argus. Biol Bull 104:156–170Google Scholar
- Maynard DM (1961) Cardiac inhibition in decapod Crustacea. In: Florey E (ed) Nervous inhibition. Pergamon, Oxford, pp 144–178Google Scholar
- Miyazaki T, Kuwasawa K, Yazawa T, Mashimo K (1985) The cardiac inhibition of a neurally mediated primary response in the shadow reflex of aquatic crustaceans. Zool Sci 2 (in press)Google Scholar
- Terzuolo CA, Bullock TH (1958) Acceleration and inhibition in crustacean ganglion cells. Arch Ital Biol 96:117–134Google Scholar
- Wiersma CAG, Novitski E (1942) The mechanism of the nervous regulation of the crayfish heart. J Exp Biol 19:255–265Google Scholar
- Yazawa T, Kuwasawa K (1984) The cardio-regulator nerves of the hermit crabs: anatomical and electrophysiological identification of their distribution inside the heart. J Comp Physiol A 154:871–881Google Scholar