Swelling and cAMP on hyperpolarization-activated Cl- conductance in rat Leydig cells.

We have used the whole cell patch-clamp technique to characterize changes in membrane conductance induced by osmotic swelling in mature rat Leydig cells dialyzed with ATP (control cells) or adenosine 3',5'-cyclic monophosphate (cAMP) plus ATP (cAMP cells). A spontaneous current activation occurs in both groups in isosmotic conditions (300/295 mosM in/out). This development is entirely counteracted in control cells and partly inhibited in cAMP cells by exposing them to a hyperosmotic (350 mosM) bath solution, and these currents increase again in a hyposmotic (205 mosM) bath solution.

Responses of ipsilateral retino-tectal (type I1) units of the frog (Rana esculenta) to moving configurational bars.

In frogs, retinal information projecting to the ipsilateral optic tectum uses a complex, at least bi-synaptic, route. Ipsilateral visual units recorded at the tectal level correspond to isthmic axon terminals. For a better approach of their visual function, these units have been stimulated with moving (V = 7.

Stimulation, data acquisition, spikes detection and time/rate analysis with a graphical programming system: an application to vision studies.

A Macintosh-based system performs stimulus control and data acquisition, and an off-line analysis, in experiments on visually driven neurons in frog. The stimulus is a target moved on a modified XY recorder. The computer is equipped with a multifunction input/output board to perform stimulus control and data acquisition.

Involvement of a pertussis toxin-sensitive G-protein in excitation-contraction coupling of intact and cut-end voltage-clamped skeletal muscle fibres.

In voltage-clamped frog muscle fibres 10 ng/ml PTX induced a decrease (approximately 35%) of tension when applied externally. Internal application in cut-end fibres significantly depressed tension after 20 min. This effect increased with time to reach 65% after 60 min.

The depressing effect of tetracaine and ryanodine on the slow outward current correlated with that of contraction in voltage-clamped frog muscle fibres.

The effects of tetracaine (10-50 microM) and ryanodine (0.1-10 microM) were tested on the slow outward K+ current (Iso) and the mechanical tension of isolated frog muscle fibres in a voltage-clamp device (double mannitol-gap) connected to a mechanoelectric transducer. In the concentration range tested, both drugs induced a simultaneous inhibition of tension and current.