Because coapplication of competitive agonists and antagonists of the same receptor could be difficult to interpret, we chose to test the effect of muscimol on sPFPs elicited by bath software of 50 m 4-AP, a well studied non-GABAergic convulsant (Rutecki et al
Because coapplication of competitive agonists and antagonists of the same receptor could be difficult to interpret, we chose to test the effect of muscimol on sPFPs elicited by bath software of 50 m 4-AP, a well studied non-GABAergic convulsant (Rutecki et al., 1987; Chesnut and Swann, 1990; Traub et al., 1995; Psarropoulou and Avoli, 1996). slices of P2 and older neocortex and P0 and older hippocampus. Mg2+-free remedy only induced spontaneous events in the majority of P2 and older slices from both areas; addition of GABAAR antagonists caused a dramatic increase in the mean amplitude, but not rate of recurrence, of these events in the hippocampus and in their mean rate of recurrence, but not amplitude, in the neocortex. In the hippocampus, GABAAR agonists suppressed amplitudes, but not rate of recurrence, of sPFPs, whereas glutamate antagonists suppressed rate of recurrence but not amplitudes. We conclude that neonatal rodent cerebral cortex possesses glutamatergic circuits capable of generating synchronous network activity and that, as with the adult, tonic GABAAR-mediated inhibition helps prevent this activity from becoming paroxysmal. (Schwartzkroin, 1981; Mueller et al., 1984; Muller et al., 1989) and of the immature rodent neocortex Timed-pregnant ICR white mouse and Sprague Dawley rat dams Etomoxir (sodium salt) (Hilltop Lab Animals, Scottdale, PA) were monitored at 12 hr intervals to determine time of delivery. The 1st 24 hr after birth were designated P0. Pups were anesthetized from the inhalation of methoxyflurane (Metofane; Mallinckrodt Veterinary, Mandelein, IL) inside a glass jar and decapitated, and the brain was eliminated into ice-cold artificial CSF (ACSF; composition in mm, NaCl 126, KCl 3, NaH2PO4 1.2, MgSO4 1.3, CaCl2 2, NaHCO3 26, and dextrose 20) saturated having a 95/5 mixture of O2/CO2. Coronal slices, 500 m solid, were cut using a Vibraslicer (WPI, Sarasota, FL) and managed for at least Etomoxir (sodium salt) 1 hr submerged inside a holding chamber filled with recirculated, oxygenated ACSF at space temp, before transfer to the recording chamber. For nominally Mg2+-free ACSF, MgCl2 was substituted by an equimolar concentration of CaCl2 (for a total of 3.3 mm CaCl2), to keep up the total divalent cation concentration. Bicuculline methchloride (BMC), SR-95531 [gabazine (GBZ)], muscimol hydrobromide, 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) disodium, d-(?)-2-amino-5-phosphonopentanoic acid (APV), and 4-aminopyridine (4-AP) were purchased from Sigma-RBI (St. Louis, MO), prepared as stock solutions in distilled water at (typically) 1000-collapse final concentration, Etomoxir (sodium salt) divided into aliquots, and stored at ?20 C. During the experiment, thawed aliquots were kept on snow and safeguarded from light until use. For electrophysiological recording, individual slices were transferred to a submersion chamber, transilluminated, and continually superfused with space temp oxygenated ACSF at 2C3 ml/min. Extracellular field potentials were recorded using glass micropipettes (1 mm outer diameter; 0.58 mm inner diameter; A-M Systems, Carlsborg, WA) drawn on a Flaming-Brown pipette puller (Sutter Tools, Novato, CA), their suggestions broken under microscopic control to a final outer diameter of 5 m, and filled with 0.9% NaCl. DC signals were recorded using a unity gain head stage connected to a 1000X gain amplifier (Intronix Systems, Bolton, Ontario, Rabbit Polyclonal to CRABP2 Canada), low-pass filtered at 1 kHz, digitized with an analog-to-digital table (National Tools, Austin, TX) at 1000 samples/sec, and streamed to disk, using software written by A.A. in the LabView environment (National Instruments). Slices were routinely managed in the recording chamber for 8 hr after the dissection without any apparent deterioration of the reactions. Data acquisition adopted one of two paradigms. In one set of experiments (observe Figs. 4-7), activity was sampled under steady-state conditions by taking records of 5 min period in control remedy, after at least 20 min in the experimental condition and after at least 20 min of washout. In these experiments, superfusion was usually stopped during the 5 min of data acquisition to remove spurious signals resulting from fluctuations in the bath level. Inside a later set of experiments (observe Figs. ?Figs.1,1, ?,2),2), activity was sampled continually for up to 64 min, throughout the wash in and washout of the experimental remedy. In these experiments, a research micropipette was placed in the bath, and its transmission was subtracted from your record, therefore eliminating the fluctuation noise. To verify that transiently preventing the.