Serotonergic regulation of the central heart auricles of Sepia officinalis L. (Mollusca, Cephalopoda).
In pharmacological bioassays on isolated isotonically suspended auricles of Sepia officinalis, the regulatory action of the neurotransmitter serotonin (5-hydroxytryptamine, 5-HT) on these autonomous contractile compartments was demonstrated. 5-HT induced concentration-dependent positive effects on frequency and tone, whereas the concentrations/response curve for the amplitude showed a biphasic course. All applied antagonists inhibited mainly the effect of 5-HT on frequency and amplitude. The chronotropic effects of 5-HT were blocked mainly by the 5-HT(1,2) antagonist methiothepin (pA(2)=8.01), the 5-HT(1a) antagonist NAN-190 (pA(2)-) and in lesser extent by the 5-HT(1,2) antagonist mianserin (pA(2)=6.81). In the presence of each antagonist applied the 5-HT action on amplitude was transformed into a positive inotropic effect with the maximum under influence of NAN-190 and the 5-HT(2,1c)-antagonist ketanserin. The auricular tone was also influenced by the antagonists and in combination with methiothepin it turned into strong negative tonotropic effect. In addition to the pharmacological bioassays, the presence of 5-HT in nerve endings within the auricle wall was demonstrated by immunohistochemical and fluorescence microscopic findings. Altogether the findings presented here confirm that 5-HT evokes excitatory effects on the autonomous contractile auricle of S. officinalis and acts obviously over different receptors, whereby a 5-HT(1)- and a 5-HT(2)-like seem to be involved.
Lehr
Tobias
T
Institut für Allgemeine und Spezielle Zoologie, Abteilung Entwicklungsbiologie, Stephanstrasse 24, D-35390 Giessen, Germany.
Schipp
Rudolf
R
D000818:Animals; D016275:Atrial Function / Q000187:drug effects / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D005453:Fluorescence; D006325:Heart Atria / Q000187:drug effects; D066298:In Vitro Techniques; D007650:Ketanserin / Q000494:pharmacology; D008803:Mianserin / Q000494:pharmacology; D008974:Mollusca; D009200:Myocardial Contraction / Q000187:drug effects; D010879:Piperazines / Q000494:pharmacology; D012701:Serotonin / Q000378:metabolism* / Q000494:pharmacology; D012702:Serotonin Antagonists / Q000494:pharmacology
D010879:Piperazines; D012702:Serotonin Antagonists; C058895:1-(2-methoxyphenyl)-4-(4-(2-phthalimido)butyl)piperazine; D008803:Mianserin; D012701:Serotonin; D007650:Ketanserin