Grass model s88 stimulator

Experiments were performed on Aplysia californica (100 to 300 g) obtained from Marinus (Newport Beach, CA, USA). Aplysia are hermaphroditic (i.e., each animal has reproductive organs normally associated with both male and female sexes). Animals were maintained in circulating artificial seawater (ASW) at 14 to 16 °C with a 12 h day-12 h night cycle.
Intracellular recordings were made using single-barrel electrodes (5 to 10 MΩ) filled with 0.6 M K₂SO₄ and 60 mM KCl. Intracellular signals were acquired using an AxoClamp 2B or 900A amplifier (Molecular Devices), a Neuroprobe amplifier (model 1600; A-M Systems), or a Getting model 5A amplifier. A Grass model S88 stimulator was used for stimulation. Extracellular signals were acquired from polyethylene suction electrodes using a differential alternating current amplifier (model 1700; A-M Systems). Recordings were made in ASW (460 mM NaCl, 10 mM KCl, 55 mM MgCl₂, 11 mM CaCl₂, and 10 mM HEPES buffer, pH 7.6) unless otherwise indicated. All chemicals were purchased from Sigma (St. Louis, MO).

Baseline afterdischarge thresholds (ADTs) in the amygdala were measured 8 weeks following surgery, using the ascending series method (Figure 1A). Subjects were placed in a corn-bedded open field chamber and connected to a Grass model S-88 stimulator (Grass Instruments, Quincy, MA, USA), which delivered pulses through the recording electrode. The subjects received a one-second train of stimulation pulses at a frequency of 60 Hz, composed of a 1 ms positive and 1 ms negative phase separated by 0.5 ms. The initial stimulus intensity was 40 μA. The current was increased in steps of 20 μA up to 400 μA, and then in steps of 40 μA from 400 μA onwards, until an afterdischarge was evoked. The interval between stimulations was 5 min. The same electrodes were used for stimulating and recording focal electroencephalographic (EEG) activity.
Baseline ADT was measured again, 2 weeks later, after which, the animals were randomized to the n-3 PUFA adequate or deficient diets (see next section). ADTs were measured once every 4–6 weeks thereafter for 34 weeks. The second baseline ADT measurement was used as the reference point of comparison for assessing subsequent changes in seizure thresholds because the first baseline threshold measurements are known to drop drastically (but plateau to some extent) following the first stimulation (16 (link)).