The pacemaker neurons of the heart ganglion are innervated from the CNS through two pairs of acceleratory nerves. The effect of acceleratory nerve stimulation was examined with intracellular electrodes from the pacemaker cells. The major effects on the pacemaker potential were an increase in the rate of rise of the spontaneous depolarization and in the duration of the plateau. The aftereffect of stimulation could last for minutes. No clear excitatory postsynaptic potential (EPSP) was observed, however. On high frequency stimulation, a small depolarizing response (the initial response) was sometimes observed, but the major postsynaptic event was the following slow depolarization, or the enhancement of the pacemaker potential (the late response). With hyperpolarization the initial response did not significantly change its amplitude, but the late response disappeared, showing that the latter has the property of the local response. The membrane conductance did not increase with acceleratory stimulation. The injection of depolarizing current increased the rate of rise of the spontaneous depolarization, but only slightly in comparison with acceleratory stimulation, and did not increase the burst duration. It is concluded that the acceleratory effect is not mediated by the EPSP but is due to a direct action of the transmitter on the pacemaker membrane.
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1 August 1969
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August 01 1969
Acceleratory Synapses on Pacemaker Neurons in the Heart Ganglion of a Stomatopod, Squilla oratoria
Akira Watanabe,
Akira Watanabe
From the Department of Physiology, Tokyo Medical and Dental University, Yushima, Bunkyo-ku, Tokyo, Japan.
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Shosaku Obara,
Shosaku Obara
From the Department of Physiology, Tokyo Medical and Dental University, Yushima, Bunkyo-ku, Tokyo, Japan.
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Toyohiro Akiyama
Toyohiro Akiyama
From the Department of Physiology, Tokyo Medical and Dental University, Yushima, Bunkyo-ku, Tokyo, Japan.
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Akira Watanabe
From the Department of Physiology, Tokyo Medical and Dental University, Yushima, Bunkyo-ku, Tokyo, Japan.
Shosaku Obara
From the Department of Physiology, Tokyo Medical and Dental University, Yushima, Bunkyo-ku, Tokyo, Japan.
Toyohiro Akiyama
From the Department of Physiology, Tokyo Medical and Dental University, Yushima, Bunkyo-ku, Tokyo, Japan.
Dr. Akiyama's present address is the Department of Neurology, College of Physicians and Surgeons, Columbia University, New York 10032
Received:
February 10 1969
Online ISSN: 1540-7748
Print ISSN: 0022-1295
Copyright © 1969 by The Rockefeller University Press
1969
J Gen Physiol (1969) 54 (2): 212–231.
Article history
Received:
February 10 1969
Citation
Akira Watanabe, Shosaku Obara, Toyohiro Akiyama; Acceleratory Synapses on Pacemaker Neurons in the Heart Ganglion of a Stomatopod, Squilla oratoria . J Gen Physiol 1 August 1969; 54 (2): 212–231. doi: https://doi.org/10.1085/jgp.54.2.212
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