Walter J Wojcik

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Baclofen and gamma-aminobutyric acid (GABA) are shown to inhibit basal adenylate cyclase activity in brain of rat. The response is mediated through the GABAB receptor, and the rank order of potency for agonists is (-)-baclofen (EC50 = 4 microM) greater than GABA (EC50 = 17 microM) greater than muscimol greater than (+)-baclofen. GABAA agonists are not(More)
There are two major classes of gamma-aminobutyric acid (GABA)-sensitive receptors: GABAA and GABAB. The GABAA receptor, the better known of the two GABA receptors, is a heterooligomeric complex that forms a chloride channel. Multiple subtypes of the GABAA receptor result from the composition of different subunits. In contrast to the GABAA receptor, the(More)
In primary cultures of cerebellar granule cells, [3H]nitrendipine binds with high affinity to a single site (KD 1 nM and Bmax 20 fmol/mg protein). The 1,4-dihydropyridine (DHP) class of compounds such as nitrendipine, nifedipine, and BAY K 8644 displace [3H]nitrendipine binding at nanomolar concentrations. Verapamil partially inhibits whereas diltiazem(More)
Stimulation of either adenosine A1 or A2 receptors results in a decrease or an increase in the adenylate cyclase activity, respectively. With various concentrations of the adenosine agonist N6-phenylisopropyladenosine, both responses on cyclase are observed in a crude membrane preparation from rat striatum. The A2 receptors appeared to be associated(More)
Three types of striatal lesions were performed to determine the site of adenosine synthesis and release and the location of adenosine A2 receptors: decortication; injection of 6-hydroxydopamine (6-OHDA) into the median forebrain bundle; and injection of kainic acid into the striatum. The parameters measured in the striatum were content of adenosine,(More)
Two alpha-adrenoreceptor blocking agents, phentolamine (5 mg/kg, IP) and phenoxybenzamine (10 mg/kg IP) were administered to rats deprived of rapid eye movement (REM) sleep for 24 hours to test the hypothesis that reduced noradrenergic transmission may abolish REM sleep rebound. The hypothesis was based on results from our previous studies which showed that(More)
gamma-Aminobutyric acidB (GABAB) receptor recognition sites that inhibit cyclic AMP formation, open potassium channels, and close calcium channels are coupled to these effector systems by guanine nucleotide binding proteins (G proteins). These G proteins are ADP-ribosylated by islet-activating protein (IAP), also known as pertussis toxin. This process(More)
In primary cultures of cerebellar granule cells, D,L baclofen (p-chlorophenyl-GABA) inhibited approximately 50% of the calcium-45 influx induced with cell depolarization. The half maximal effective concentration for baclofen was 4 nM. Basal calcium influx was not influenced by baclofen thus suggesting that its inhibitory action could be exerted via a(More)
Activation of muscarinic receptors with carbachol has no effect on intracellular Ca2+ concentration in cerebellar granule cell cultures. Only after elevating intracellular Ca2+ concentrations using either 40 mM KCl or activating glutamatergic receptors was carbachol able to increase intracellular Ca2+. The response lasted about 10 s, and the median increase(More)
In cerebellar granule cells, baclofen acted with micromolar concentrations at proposed gamma-aminobutyric acid-B receptors to inhibit the formation of cyclic AMP and depolarization-induced release of glutamate. Nanomolar concentrations of baclofen inhibited depolarization-induced influx of calcium. All three responses to baclofen were attenuated after(More)