Characterization of stretch-activated calcium permeable cation channels in freshly isolated myocytes of the cricket (Gryllus bimaculatus) lateral oviduct

Stretch-activated channels (SACs) were investigated in myocytes isolated from the lateral oviduct in cricket Gryllus bimaculatus using the cell-attached or excised inside-out patch clamp technique. Application of both negative and positive pressure (10-100 cm H(2)O) into the patch pipettes induced the unitary channel current openings. The open probability (NPo) of the channel increased when negative pressure applied into the patch pipettes increased. The single channel conductance for this channel was approximately 20 pS with 140 mM Na(+), K(+), or Cs(+) in the patch pipettes and was approximately 13 pS with 100mM Ca(2+) or Ba(2+) in the patch pipettes. External application of Gd(3+), La(3+), Cd(2+) and Zn(2+)inhibited the channel with the IC(50) values of 14, 15, 28, and 18 microM respectively. Interestingly external application of TEA, a specific blocker of K(+) channel, also inhibited this channel with IC(50) value of 8.8mM. These results show for the first time the presence of stretch activated Ca(2+)-permeable nonselective cation channel in myocytes isolated from the cricket lateral oviduct. The physiological significance of this channel in oviposition behavior is discussed.