Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0043167 (pertussis)
 19,595 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The cortex of the rabbit (Oryctolagus cuniculus) is rich in melatonin binding sites, and particularly abundant is the parietal cortex. Consequently, we characterized the putative melatonin receptor in the parietal cortex by a series of in vitro ligand-receptor binding experiments and biochemical and electrophysiological studies. The in vitro saturation and competition experiments demonstrated that the binding in the crude cortical membrane preparations was of high affinity and specificity. Guanine nucleotides (GDP, GTP, and GTP gamma S) inhibited the specific 2-[125I]iodomelatonin binding in a dose-dependent manner. Coincubation with a nonhydrolyzable GTP analog provoked a shift in the binding affinity; the numerical values of the Kd increased from 20-30 to 200-600 pM. Melatonin, in nanomolar concentrations, was able to inhibit the forskolin-stimulated accumulation of cAMP in parietal cortex explants, and preincubation with pertussis toxin counteracted this effect of melatonin. Apparently, the melatonin binding site in the rabbit parietal cortex is linked to its second messenger via a pertussis toxin-sensitive G-protein, probably of the inhibitory Gi class, similar to what has been described for different parts of the brain of other vertebrates. The experiments on the spontaneous firing activity of single neurons in the third to fourth layer of the parietal cortex in anesthetized animals showed that melatonin and its potent agonist 2-iodomelatonin exhibited gamma-aminobutyric acid (GABA)-like effects and were able alone, in nanomolar concentrations, to significantly slow the neuronal firing activity. Moreover, both melatonin and 2-iodomelatonin potentiated the effect of GABA on the neuronal activity, leading to powerful inhibition of the tested neurons. Undoubtedly, the binding site in the rabbit parietal cortex possesses all of the characteristics of a functional receptor. We suggest that melatonin is involved in the control of fundamental cortical functions and that it acts in concert with GABA, one of the two major inhibitory neurotransmitters in the central nervous system.
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PMID:Melatonin signal transduction and mechanism of action in the central nervous system: using the rabbit cortex as a model. 131 48

Intracellular recordings were obtained from the basolateral amygdala in in vitro rat brain slice preparations to examine whether gamma-aminobutyric acid (GABA)B receptors are altered after in vivo kindling-induced epileptogenesis. Stimulating the stria terminalis evoked excitatory (EPSPs) and inhibitory (IPSPs) postsynaptic potentials in control neurons, and epileptiform bursting or enhanced EPSPs, but no IPSPs, in neurons from animals, 4 to 8 weeks after the last kindled seizure. Baclofen (0.1 nM-100 microM) depressed EPSPs in control and kindled basolateral amygdala neurons, but the EC50 appeared to be shifted 100-fold from 5 nM in control to 500 nM in kindled neurons. Further analysis suggested a high-affinity component may be affected in kind led neurons. The absence of IPSPs in kindled neurons could not account for this shift, because effects of baclofen on EPSP amplitude were reduced in kindled animals even when GABAA receptors were blocked with bicuculline methiodide (30 microM) and postsynpatic GABAB receptors with intracellular guanosine 5'-O-3-thiotriphosphate (10 mM); 6-cyano-2,3-dihydroxy-7-nitroquinoxaline (10 microM) was also present to block bicuculline methiodide-induced bursting. Membrane responses to exogenously applied N-methyl-D-aspartate and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid were not affected by baclofen. Baclofen also hyperpolarized basolateral amygdala neurons and reduced membrane input resistance with an EC50 of 1 microM in control and kindled neurons. Post- but not presynaptic effects of baclofen were blocked by 2-hydroxy-saclofen (100 microM) and pertussis toxin pretreatment. In conclusion, kindling-induced epileptogenesis reduces the sensitivity of presynaptic GABAB receptors, an effect which may contribute to the enhancement of excitatory transmission in kindled animals. Furthermore, different pharmacological properties of pre- and postsynaptic receptors in the amygdala suggest two distinct populations of GABAB receptors whose long-lasting responses to kindling-induced seizures are different.
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PMID:Epileptogenesis reduces the sensitivity of presynaptic gamma-aminobutyric acidB receptors on glutamatergic afferents in the amygdala. 132 20

Serotonin is a neuromodulator that mediates a wide range of effects by interacting with multiple receptors. Using a strategy based on nucleotide sequence homology between genes encoding receptors that interact with guanine nucleotide-binding proteins, we have isolated a mouse gene encoding an additional serotonin receptor. When expressed in cultured cells, it displayed the pharmacological profile and coupling with adenylate cyclase characteristic of the 5HT1B receptor subtype. In NIH 3T3 cells expressing this receptor, serotonin induced a decrease in forskolin-stimulated cAMP levels. This effect was blocked by pertussis toxin, indicating that the 5HT1B receptor interacts with a pertussis toxin-sensitive guanine nucleotide-binding protein. To obtain clues as to the possible function of the 5HT1B receptor, we have analyzed its pattern of expression in the adult mouse brain by in situ hybridization. Our results, together with previous autoradiographic studies, suggest that the 5HT1B receptors are localized presynaptically on the terminals of striatal neurons and Purkinje cells and that they might modulate the release of neurotransmitters such as gamma-aminobutyric acid. The predominant expression of the 5HT1B receptor in the striatum and cerebellum points to an involvement of this receptor in motor control.
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PMID:Mouse 5HT1B serotonin receptor: cloning, functional expression, and localization in motor control centers. 155 7

To elucidate the possible involvement of GTP-binding proteins (G proteins) in the mechanism of exocytosis, we studied effects of pertussis toxin (PTX), guanosine 5'-O-(3-thiotriphosphate) (GTP-gamma-S), and antibodies against the G proteins (Gi and G(o)) on the secretory function of bovine adrenal chromaffin cells. Pretreatment of chromaffin cells with PTX resulted in an increase in acetylcholine-evoked catecholamine release. High K(+)-, histamine-, or gamma-aminobutyric acid-evoked catecholamine release was also potentiated by PTX pretreatment. The concentration of extracellular Ca2+ required for maximal release by 10(-4) M acetylcholine was decreased significantly in PTX-treated cells. In digitonin-permeabilized cells, PTX pretreatment resulted in a decrease of the half-maximal concentration (Km) of Ca2+ required for exocytosis with no significant change in the maximal stimulation (Vmax). Exposure of permeabilized cells to GTP-gamma-S (a nonhydrolyzable GTP analogue) inhibited Ca(2+)-dependent exocytosis by reducing the affinity for Ca2+. The effects of PTX pretreatment were mimicked by treatment of permeabilized cells with polyclonal antibodies selective for the alpha subunit of the PTX-sensitive G protein, G(o). Treatment with similar antibodies against the alpha subunit of Gi had no effect. These findings suggest that G(o) directly controls the Ca(2+)-triggered process in the machinery of exocytosis by lowering the affinity of the unknown target for Ca2+.
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PMID:Regulatory role of the GTP-binding protein, G(o), in the mechanism of exocytosis in adrenal chromaffin cells. 157 7

Ca signals in bovine adrenal chromaffin cells were studied both in Fura-2/AM-loaded intact cells, and in voltage-clamped cells under whole-cell patch-clamp conditions. The effects of gamma-aminobutyric acid b subtype (GABAb) receptor activation on K(+)-depolarization-induced signals and on voltage-activated Ca2+ currents were investigated. Both GABA (20 microM) plus bicuculline (20 microM) and (-)baclofen (20-100 microM), effectively inhibited the Ca signal in intact cells. The effects caused by baclofen continued to develop during the time interval between two successive stimuli. The restoration of the Ca signal during washout of baclofen was also delayed and continued in some experiments for 10-20 min. The inhibitory effect of baclofen on the Ca signal was eliminated by pre-treatment of the cells with pertussis toxin (PTX, 1 micrograms/ml, for 4-6 h at 37 degrees C). Baclofen (50 microM) inhibited Ca2+ current in whole-cell mode by at most 20%. The effect developed quickly and was reversible. Infusion into the cells of a non-hydrolyzable analogue of guanosine 5'-triphosphate GTP gamma S (100 microM), led to complete inhibition of the Ca2+ conductance and of voltage-evoked intracellular Ca ([CA]i) transients within 2 min. In paired cells intracellularly perfused with GTP gamma S-free solution, the Ca2+ current amplitude decreased by only about 30% for 5-6 min. It is concluded that bovine chromaffin cells have functional GABAb receptors the activation of which, mediated by a PTX-sensitive GTP-binding protein, inhibits the evoked increase in cytosolic free Ca2+.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Pertussis-toxin-sensitive inhibition by (-) baclofen of Ca signals in bovine chromaffin cells. 166 9

1. We examined the effects of gamma-aminobutyric acid (GABA) and baclofen on pre- and postsynaptic membrane conductances in dissociated rat hippocampal cells. Both GABA (5 microM with 10 microM-bicuculline) and baclofen (50 microM) caused small but significant increases in membrane conductance that were blocked by 2-hydroxysaclofen (100 microM), a GABAB receptor antagonist. This increase in membrane conductance seems to be mediated by GABAB receptors. 2. At a low concentration of GABA (1 microM) which has a very small direct postsynaptic effect on GABAA receptors, no postsynaptic GABAB effect was detected. However, at this concentration, GABA near maximally attenuated both excitatory and inhibitory synaptic currents. This GABA effect on transmitter release was significantly attenuated by 2-hydroxysaclofen. 3. Baclofen was also more potent in attenuating the inhibitory synaptic conductance than increasing postsynaptic conductance. Concentrations below 1 microM diminished synaptic currents by greater than 50%. At these low baclofen concentrations 2-hydroxysaclofen significantly attenuated baclofen's reduction of synaptic currents. 4. The effects of GABA and baclofen on synaptic conductances were blocked by pretreating the cultures with pertussis toxin, suggesting that a GTP-associated protein, Gi or Go is responsible for reducing transmitter release. 5. Despite the ability of GABA to diminish inhibitory synaptic currents through GABAB receptor activation, we observed no effect of 2-hydroxysaclofen on paired-pulse depression. Therefore, these presynaptic GABAB receptors may not be true 'autoreceptors'. 6. Our findings indicate that in culture, at least, the presynaptic GABAB effect responsible for synaptic modulation has a pharmacological profile similar to the postsynaptic GABAB effect. At present, it is unnecessary to postulate two different types of GABAB receptors.
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PMID:The modulation of rat hippocampal synaptic conductances by baclofen and gamma-aminobutyric acid. 166 62

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 pertussis toxin pretreatment of cell cultures. The inhibition of calcium influx and glutamate release were reversed by the cyclic AMP analog, 8-(4-chlorphenylthio)-cyclic AMP. The release of glutamate was dependent on the influx of extracellular calcium, which enters the cell through dihydropyridine-sensitive voltage-dependent calcium channels. Because the decrease in calcium influx by baclofen and nifedipine were additive, the baclofen-mediated decrease in calcium influx may not involve a dihydropyridine-sensitive calcium channel. These results show similarities between the baclofen-mediated inhibition of cyclic AMP formation and glutamate release, suggesting a relationship between these two events. The baclofen-mediated inhibition of calcium influx may not be related to baclofen's inhibition of glutamate release.
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PMID:gamma-Aminobutyric acid-B receptors inhibit glutamate release from cerebellar granule cells: consequences of inhibiting cyclic AMP formation and calcium influx. 167 50

Transmembrane currents induced by (-)-baclofen (BAC), a specific agonist of the gamma-aminobutyric acid-B (GABAB) receptor, in Xenopus oocytes injected with guinea pig cerebral mRNA were electrophysiologically and pharmacologically characterized under a voltage-clamp condition. The oocytes injected with mRNA acquired responsiveness to BAC and showed two types of currents at a holding potential of -50 mV. One was the slow and smooth inward current which had a short latency and associated with a decrease in membrane conductance, and its amplitude was decreased by hyperpolarization and increased by depolarization. The other was the large fast oscillatory inward current with a long-latency, which was decreased in amplitude by depolarization and reversed at -26 mV. Both currents were not blocked by bicuculline but were depressed by 2-hydroxysaclofen (2-OH-SAC), though the smooth current was less sensitive to 2-OH-SAC; about 40% blockade at the 2-OH-SAC concentration capable of abolishing the oscillatory current. The smooth current was depressed by Ba2+. The oscillatory current was time-dependently attenuated and almost abolished by intracellularly injected pertussis toxin (PTX), while the smooth current was not depressed by this toxin even when the oscillatory current was nearly abolished. The intracellular injection of GTP-gamma-S into oocytes attenuated both oscillatory and smooth currents. These results suggest the possibility that GABAB receptors expressed in Xenopus oocytes by cerebral mRNA are functionally coupled with two signal transduction systems, one is the opening of Ca2(+)-dependent Cl- channels mediated by PTX-sensitive GTP-binding protein(s) and the other is the closure of K+ channels through PTX-insensitive GTP-binding protein(s).
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PMID:GABAB receptors expressed in Xenopus oocytes by guinea pig cerebral mRNA are functionally coupled with Ca2(+)-dependent Cl- channels and with K+ channels, through GTP-binding proteins. 170 75

The effects of gamma-aminobutyric acid (GABA) and isoguvacine on the thyrotropin (TSH) secretion stimulated by thyrotropin releasing hormone (TRH), were investigated in vitro with perifused rat pituitaries. At nanomolar concentrations the two agonists induced potentiation of the TRH-induced TSH release. The potentiation was blocked by SR 95531 a specific GABAA antagonist. The isoguvacine potentiation of the TSH response to TRH failed to occur when cobalt (Co2+) was added to the perifused medium. Nifedipine completely blocked the GABA or isoguvacine potentiation of the TSH response while omega-conotoxin did not modify it. Pre-perifusion of the pituitaries with pertussis toxin did not change the TSH response to TRH but completely inhibited the isoguvacine potentiation of the response. Our results demonstrate that the GABA potentiation of TRH-induced TSH release occurring through the stimulation of GABAA receptor sites is a calcium (Ca2+)-dependent phenomenon, probably mediated by activation of dihydropyridine (DHP)-sensitive, omega-conotoxin-insensitive Ca2+ channels involving a pertussis toxin-sensitive G protein.
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PMID:Involvement of dihydropyridine-sensitive calcium channels in the GABAA potentiation of TRH-induced TSH release. 170 71

The stimulation of postsynaptic gamma-aminobutyric acid (GABA)B receptors leads to slow inhibitory postsynaptic potentials due to the influx of K(+)-ions. This was studied biochemically, in vitro in mammalian cultured spinal cord neurons by using 86Rb as a substitute for K+. (-)-Baclofen, a GABAB receptor agonist, produced a concentration-dependent increase in the 86Rb-influx. This effect was stereospecific and blocked by GABAB receptor antagonists like CGP 35 348 (3-aminopropyl-diethoxymethyl-phosphonic acid) and phaclofen. Apart from the GABAB receptors, both adenosine via adenosine1 receptors and 5-hydroxytryptamine (5-HT) via 5-HT1 alpha agonists also increased the 86Rb-influx. These agonists failed to show any additivity between them when they were combined in their maximal concentration. In addition, their effect was antagonized specifically by their respective antagonists without influencing the others. These findings suggest the presence of GABAB, adenosine1 and 5-HT1 alpha receptors in the cultured spinal cord neurons, which exhibit a heterologous regulation of the same K(+)-channel. The effect of these agonists were antagonized by phorbol 12,13-didecanoate, an activator of protein kinase C, and pretreatment with pertussis toxin. This suggests that these agonists by acting on their own receptors converge on the same K(+)-channel through the Gi/Go proteins. In summary, we have developed a biochemical functional assay for studying and characterizing GABAB synaptic pharmacology in vitro, using spinal cord neurons.
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PMID:A functional assay to measure postsynaptic gamma-aminobutyric acidB responses in cultured spinal cord neurons: heterologous regulation of the same K+ channel. 184 95


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