Article 11
Receptor differentiation and mechanisms of signal transduction in the circulatory system of Sepia officinalis
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R. SCHIPP*, T. LEHR
Institut für Allgemeine und Spezielle Zoologie, Justus-Liebig-Universität Giessen, Stephanstrasse 24, 35390 Giessen, Germany
* corresponding author:
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ABSTRACT. – Considering most recent pharmacological as well as histo- and biochemical findings, receptor differentiations and mechanisms of signal transduction in central organs of the circulatory system of Sepia officinalis are demonstrated. In this easily available species the systemic and branchial heart, the cephalic aorta and vein as well as the branchial vein are well accessible to experimental studies; these studies suggest:
1. The neurotransmitters: acetylcholine (ACh), noradrenaline (NA), adrenaline (A), dopamine (DA), 5-hydroxytryptamine (5-HT), FMRFamide and nitric oxide (NO) are involved in the neuroregulation showing very different action profiles in the organs mentioned.
2. As in vertebrates there is a general but differing excitatory-inhibitory antagonism between monoamines and ACh.
3. The ACh-receptor seems to be of a nicotinic type, mediating inhibitory actions in the heart organs and arteries but a peristalsis activation in the cephalic vein.
4. Catecholamines act by an α1-like receptor coupled with the PI-cycle, that is ascertained for the cephalic aorta, the systemic and branchial heart; for the auricle and branchial vein additionally a β-like cAMP coupled receptor seems probable.
5. 5-HT is an essential neurotransmitter in all the organs studied; in the denselyinnervated, autonomously contractile auricle, the central motor of the blood circulation, four different receptors seem to be established: a 5HT1– and 5-HT4-like receptor, cAMP coupled and a 5-HT2-like receptor, PI-response-coupled as well as a 5-HT3-like receptor that is probably an ion channel.
6. NO is demonstrated for the cephalic aorta and the rhythmically contractile bulbus of the branchial heart, mediating inhibitory and dilatatory actions by the cGMP mechanism.
