The enterins inhibit the contractile activity of the anterior aorta of Aplysia kurodai.
2002
SUMMARY The anterior aorta is one of the largest blood vessels in the marine
mollusc Aplysia kurodai . We examined the actions of recently
identified neuropeptides, the enterins, on this blood vessel.
Immunohistochemistry revealed that the enterin-immunopositive nerve fibers and
varicosity-like structures are abundant in the aorta. When the enterins were
applied to the aorta, the basal tonus of the arterial muscles was diminished.
The enterins also decreased the contraction amplitude of the anterior aorta
evoked either by the application of an Aplysia cardioactive peptide,
NdWFamide, or by the stimulation of a nerve innervating the aorta (the vulvar
nerve). We found that the enterins activate the 4-aminopyridine
(4-AP)-sensitive K + channels, and thereby hyperpolarize the
membrane potential of the aortic muscles. In the presence of 4-AP, the
enterins failed to inhibit the muscle contraction evoked by the vulvar nerve
stimulation, suggesting that the inhibition is mainly due to the activation of
the 4-AP-sensitive K + channels. The inhibition of the
NdWFamide-evoked contraction by the enterin was not, however, affected by
4-AP. These results suggest that the enterins are involved in inhibitory
regulation of the contractile activity of the anterior aorta, and that the
inhibition could be due to multiple mechanisms.
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