Suction electrode

Figure 4.5 Influence of oxidant stress on action potentials recorded In an isolated rabbit ventricular myocyte, (a) Control action potential, (b) Action potential recorded 3 min after exposure to oxidant stress induced by the photoactivation of rose bengal (50 nu). (c) Spontaneous and repetitive action potential discharges induced 6.5 min after exposure to rose bengal. Action potentials were recorded via a 2.5 MQ suction electrode and a current-clamp amplifier. The cell was stimulated at 0.1 Hz with a 2 ms suprathreshold current pulse and, when the cell showed automaticity (after 6 min), stimulation was stopped. Redrawn from Matsuura and Shattock (1991b).

The second technique is the hemisected spinal cord in vitro, initially of amphibia but now more commonly of neonatal rats [6]. Grease-seals or suction electrodes are used to record DC potentials or synaptic responses from ventral or dorsal roots. Since compounds are usually added to the bathing solution, more quantitative information from this in vitro preparation can be obtained than fi-om microelectrophoresis experiments in vivo. 

Figure 4. Experimental chamber for recording from the 6th abdominal ganglion of the cockroach. The ganglion (black) is placed in a wax chamber (shaded) and the nerve cord is embedded in vaseline, thus isolating the cut end of the nerve cord from the ganglion. A stimulus pulse (p) was applied to the cereal nerve via a suction electrode (s). Recordings from the nerve cord were made via silver wire electrodes (e), and chemicals were added to the left side of the saline-filled chamber Copyright 1986 American Cyanamid Co. Reprinted with permission.

To first obtain an ECG the patient must be physically connected to the amplifier front end. The patient/amplifier interface is formed by a special bioelectrode that converts the ionic current flow of the body to the electron flow of the metallic wire. These electrodes typically rely on a chemical paste or gel with a high ionic concentration. This acts as the transducer at the tissue-electrode interface. For short-term applications the use of silver-coated suction electrodes or sticky metallic foil electrodes are... 

FIGURE 4.4 Examples of different skin electrodes (a) metal plate electrodes, (b) suction electrode for EGG, (c) metal cup EEG electrode, (d) recessed electrode, (e) disposable electrode with electrolyte-impregnated sponge (shown in cross section), (f) disposable hydrogel electrode (shown in cross section), (g) thin-film electrode for use with neonates (shown in cross section), and (h) carbon-filled elastomer dry electrode. 

Figure 8.6. Suction electrode. A more sophisticated version uses a silver-silver chloride button electrode imbedded in the wall of a plastic electrode holder. Only the pore tip is glass. Suction is obtained via a thin catheter tube attached to a standard hypodermic syringe.

A particular type of suction electrode used in neurological studies was described in Chapter 8. Various gross suction electrodes have been developed for body-surface recording from animals and man. The most commonly used is the precordial suction-cup electrode in electrocardiography. 

Since suction electrodes are basically recessed electrodes, problems with electrical contact can develop. One must use a good wetting electrolyte to insure maintenance of a high-integrity electrical connection. 

Note Alternatively, stain a small number of NMls by stimulating a single nerve in HL3 with dye (and no high K+) using a suction electrode. As the nerve innervates only a few muscles in a single abdominal or thoracic domain, only few NMls are labeled. 

Figure 15.1. Drosophila embryonic neuromuscular preparation. Top panel) Dissected Drosophila embryo viewed with a scanning electron microscope (SEM) anterior (A) to the left, posterior (P) to the right. The prominent CNS lies along the ventral midline. Bottom panel) Schematic drawing of the four ventral longitudinal muscles in one segment. The CNS, peripheral nerve, and NMJ on these four muscles are drawn. The typical recording configuration involves whole-cell patch-clamp recording from muscle 6 and suction-electrode stimulation of the peripheral nerve.

Suction Electrode Motor Nerve Stimulation. The most common way to stimulate synaptic transmission at the NMJ is with a glass suction electrode on the segmental nerve (Figure... 

Direct CNS Stimulation. An alternative to the standard suction electrode stimulation of the peripheral nerve is direct stimulation of the CNS (Nishikawa and Kidokoro 1995). A microelectrode filled with 3-4 M KCl or potassium acetate is inserted into the middle of the ventral ganglion and positive pulses of approximately 2 pA in intensity and approximately 2 msec in duration are delivered (Dietcher et al. 1998). Synaptic transmission is recorded in the patch-clamped muscle in the standard configuration. 

Figure 15.2. Drosophila larval neuromuscular junction system. A wandering third-instar larva is dissected open to reveal the ventral neuromusculature (see Figure 15.1). The peripheral nerve is severed and stimulated with a glass suction electrode. The muscle is recorded from in two-electrode voltage-clamp (TEVC) configuration. The postsynaptic excitatory junctional current (EJC) is recorded to assay synaptic transmission bottom inset). Top inset) Basis of synaptic transmission event being evoked by nerve stimulation and recorded via ion flux through muscle glutamate receptors.

Conventional intracellular voltage recording of synaptic potentials (EJPs [excitatory junctional potentials] Jan and Jan 1976a) is the most traditional and simplest electro-physiological technique. The muscle is impaled with a single sharp electrode filled with 3 M KCl or potassium acetate (15-40 M 2 resistance). Nerve-evoked EJPs are recorded by stimulating the appropriate segmental nerve (0.2-1 msec) with a fire-polished suction electrode (see above). 

The PDMN may be cut with fine scissors approximately 20-40 jim from the thoracic ganglion. The entire nerve is sucked into a glass suction electrode (5-10- im inner diameter)... 

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