Effects of neuroactive agents on the isolated heart activities of marine bivalve Meretrix lusoria.
By recording method, we measured simultaneously both the contractile force (CF) and the action potential (AP) of the isolated heart to confirm the chief cardioregulatory transmitters of a marine bivalve. The effects of several neuroactive agents on CF, HR and the amplitude of AP in marine bivalve were investigated. Acetylcholine and carbachol produced inhibitory effects on the heart performance at 1.0 x 10(-11) M. Choline also exhibited inhibitory effects at a higher concentration, but atropine, curare, pilocarpine and hexamethonium bromide (all at 1.0 x 10(-4) M) exerted no significant effects on the spontaneous cardiac activities. 5-HT and 8-OH-DPAT produced positive chronotropic and inotropic effects on the heart at 1.0 x 10(-8) M, whereas adrenaline and dopamine were positively inotropic at 1.0 x 10(-5) M. The perfusion of adrenaline or dopamine typically prolonged the plateau duration of the action potential, and then enhanced CF. However, histamine, GABA and PGF2 alpha all exerted no significant effect on either CF or the amplitude of AP of the isolated heart. The results indicate that 5-HT and acetylcholine are excitatory and inhibitory agents, respectively, that regulate the isolated cardiac performance in a marine bivalve. The mechanism of positively inotropic effects of biogenic amines is discussed.
Lee
C M
CM
Department and Institute of Biology, National Taiwan Normal University, Taipei, Republic of China.
Lin
J T
JT
Tsai
T S
TS
D000109:Acetylcholine / Q000494:pharmacology; D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D015306:Biogenic Monoamines / Q000494:pharmacology; D049872:Bivalvia; D006321:Heart / Q000187:drug effects* / Q000502:physiology; D066298:In Vitro Techniques; D009200:Myocardial Contraction / Q000187:drug effects*; D018377:Neurotransmitter Agents / Q000494:pharmacology*
D015306:Biogenic Monoamines; D018377:Neurotransmitter Agents; D000109:Acetylcholine