Cholinergic regulation of body-wall muscle contraction of the ascidian Styela rustica (Linnaeus, 1767)

Abstract

The regulation of body wall muscle contraction in the ascidian Styela rustica was studied. Acetyl choline (ACh, 1-10 μM) induced a significant contraction of isolated muscle strips. The ACh induced con tractile response was potentiated and prolonged in the presence of proserine (15 μM), which confirms ace tylcholinesterase activity in the S. rustica body wall muscle. Atropine (1-100 μM, M cholinoreceptor blocker) did not prevent the ACh induced contractile response, while d tubocurarine (1-100 μM, N choli noreceptor blocker) progressively reduced muscle contraction induced by 10 μM ACh. Thus, neuromuscular transmission in the S. rustica body wall muscle is mediated by nicotinic like ACh receptors. Procaine reduced ACh induced (10 μM) muscle contraction. As well, our experiments showed spontaneous rhythmic contractile activity in isolated muscle strips of S. rustica. Atropine, d tubocurarine, procaine, and proserine did not alter rhythmic activity. Myogenic automaticity is suggested as a possible cause of the rhythmic con traction of the ascidian body wall muscle.

Pharmacological analysis of the transmembrane action potential configuration in myoepithelial cells of the spontaneously beating heart of the ascidianStyela rustica in vitro

“…Ascidians Styela rustica Linnaeus 1767 (Ascidiacea, Tunicata) (n=23; body mass 6±1 g, body height 65±5 mm) were collected by SCUBA divers from a depth of 2-10 m in the vicinity of the White Sea Biological Station, Moscow State University (Kandalaksha Bay, Karelia, Russia; 66°34′N, 33°08′E), in July-August 2013. Prior to experiments, the animals were kept in aquariums with running seawater at 8±1°С for 1-8 days, as described previously (Kuzmin et al, 2012).…”

“…The composition of the water was as follows: 280 mmol l −1 NaCl, 6 mmol l −1 KCl, 1.6 mmol l −1 NaHCO 3 , 36 mmol l −1 MgCl 2 , 7 mmol l −1 CaCl 2 , 19 mmol l −1 Na 2 SO 4 , 0.5 mmol l −1 KBr and 0.5 mmol l −1 NaF. Water salinity in the White Sea is 24‰; its pH was adjusted to 8.1±0.2 (Kuzmin et al, 2012).…”