Different excitation-contraction coupling mechanisms exist in squid, cuttlefish and octopod mantle muscle

C. M. Rogers, L. Nelson, B. J. Milligan, E. R. Brown

Research output: Contribution to journalArticlepeer-review

10 Citations (Scopus)

Abstract

Excitation-contraction (EC) coupling was studied in central zone mantle muscle fibres of a squid (Alloteuthis subulata), a cuttlefish (Sepia officinalis) and an octopod (Eledone cirrhosa). Thin slices of muscle were used for twitch experiments and enzymatic isolation of single fibres for whole-cell patch-clamp studies. The current required for a supramaximal twitch response during direct stimulation of muscle slices was lower for squid than for cuttlefish. In squid, but not in cuttlefish, the current-response relationship was independent of slice thickness (range 0.1-0.5 mm). Twitches of squid and cuttlefish slices were reversibly abolished by removal of extracellular Ca2+. In squid, but not in cuttlefish, the current-response relationship was Na+-dependent, and in the absence of Na+ higher current strengths were required to generate a supramaximal response. In whole-cell voltage-clamp experiments on isolated muscle fibres from squid, cuttlefish and Eledone cirrhosa, a sustained inward current was recorded upon depolarisation. This current was blocked by 5 mmol l-1 Co2+ and suppressed by 10 micromol l-1 nifedipine. In squid, an additional inward fast-activating transient current was seen which was blocked by 2 micromol l-1 tetrodotoxin and depolarised holding potentials. The fast current represents a voltage-activated Na+ channel, and the slow currents represent L-type Ca2+ channels. We conclude that squid possess a specialised rapid EC coupling mechanism in central zone fibres that is absent in cuttlefish and Eledone cirrhosa.

Original languageEnglish
Pages (from-to)3033-3041
Number of pages9
JournalJournal of Experimental Biology
Volume200
Issue number23
Publication statusPublished - Dec 1997

Fingerprint

Dive into the research topics of 'Different excitation-contraction coupling mechanisms exist in squid, cuttlefish and octopod mantle muscle'. Together they form a unique fingerprint.

Cite this