Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

Query: EC:1.14.16.2 (tyrosine hydroxylase)
14,760 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The acetone precipitation of a partially purified tyrosine 3-monooxygenase (L-tyrosine, tetrahydropteridine: oxygen oxidoreductase (3-hydroxylating), EC 1.14.16.2) resulted in the complete loss of enzymatic activity. The enzymatic activity was restored by incubation with iron and dithiothreitol. The restoration of the activity was a pH-, temperature- and time-dependent reaction. Since cobalt, nickel, copper, zinc, manganese, cadmium, magnesium calcium and barium ions were all ineffective in restoring activity, iron ion appeared to be specifically required in the restoration of the enzyme activity. Dithiothreitol could be partially replaced in the restoration step by glutathione, 2-mercaptoethanol or cysteine.
...
PMID:Inactivation of tyrosine 3-monooxygenase by acetone precipitation and its restoration by incubation with a sulfhydryl agent and iron. 611 46

Enhancer elements regulating the neuronal gene, tyrosine hydroxylase (TH), were identified in TH-expressing peripheral nervous system PATH and central nervous system CATH cell lines. Mutational analysis in which rat TH 5'-flanking sequences directed chloramphenicol acetyltransferase (CAT) reporter gene expression demonstrated that mutating the cyclic AMP response element (CRE) at -45 base pair reduced expression by 80-90%. A CRE linked to an enhancerless TH promoter fully supported expression. Cotransfection of a dominant-negative CREB protein reduced expression 50-60%, suggesting that the CRE is bound by CREB or a CREB dimerization partner. Although mutating the AP1/dyad (AD) element at -205 base pair only modestly reduced CAT levels, AD minimal enhancer constructs gave 45-80% of wild type expression when positioned at -91 or -95. However, in its native context at -205, the AD could not support expression. In contrast, a CRE, moved from its normal position at -45 to -206, gave full activity. These results indicate that the CRE is critical for TH transcription in central nervous system CATH and peripheral nervous system PATH cells, whereas the AD is less important and its enhancer activity is context-and/or position-dependent. These results represent the first attempts to map regulatory elements directing TH expression in central nervous system cell lines.
...
PMID:The cyclic AMP response element directs tyrosine hydroxylase expression in catecholaminergic central and peripheral nervous system cell lines from transgenic mice. 766 71

1. Intracellular microelectrode and whole-cell patch-clamp recordings were obtained from adult guinea pig celiac ganglion neurons grown in tissue culture for 7-14 days. Over 90% of neurons showed phasic-type action-potential discharge with the use of either type of recording electrode; they stained immunohistochemically for catecholamines, tyrosine hydroxylase, and neuropeptide Y. Input resistance (140 M omega) and action-potential amplitude (103 mV) were significantly greater with whole-cell than with microelectrode recordings, but other passive electrical properties were similar. 2. Five potassium currents were characterized: an apamin-sensitive after hyperpolarizing current (IAHP), an apamin and tetraethylammonium-insensitive slow IAHP, an M-like current, a transient outward IA current, and a delayed rectifier IK current. A hyperpolarization-activated cationic Ih current was also present. The first three currents were not observed with whole-cell recordings. 3. Cadmium (200 microM), cobalt (1 mM), lanthanum (30 microM), or a low calcium/high magnesium solution blocked both IAHPS and the M-like current; barium (1 mM) also blocked these currents. 4. Kinetics of the M-like current were best described by a double exponential fit to deactivating tail currents with time constants of 50 and 390 ms at -50 mV. The apamin-sensitive and slow IAHP decayed exponentially with time constants of 145 ms and 3.5 s, respectively. There was no correlation between occurrence of M-like current (95% of neurons) and slow IAHP (40% of neurons), nor any correlation between magnitude of M-like current and IAHP in those cells exhibiting both currents. 5. Muscarine and substance P (SP) caused depolarizations or inward currents (under voltage clamp) at the resting potential (-55 mV) associated with a decreased membrane conductance. The slow IAHP and the M-like current, but not the apamin-sensitive IAHP nor the IA, were blocked by muscarine and SP (IC50 3 microM and 100 nM, respectively). Muscarine and SP also decreased a "leak" potassium current. 6. We conclude that celiac neurons express two calcium-dependent IAHP currents and a calcium-dependent M-current; these are seen by fine-tipped intracellular microelectrodes but not by whole-cell patch electrodes. These currents are not required for spike frequency accommodation. Muscarine and SP reduce these currents, as well as voltage-independent leakage potassium current.
...
PMID:Potassium currents and their modulation by muscarine and substance P in neuronal cultures from adult guinea pig celiac ganglia. 768 76

In the rostral ventrolateral medulla (RVLM), angiotensin II (Ang II) receptors are concentrated in the region that contains neurons innervating sympathetic preganglionic neurons. We sought to determine whether these bulbospinal cells are sensitive to Ang II. Retrogradely labeled bulbospinal RVLM neurons (N = 125) were recorded in thin slices from neonatal rats. Most (33 of 46) histologically recovered bulbospinal neurons were C1 cells (immunoreactive for tyrosine hydroxylase [TH-ir] or phenylethanolamine N-methyltransferase [PNMT-ir]). Bulbospinal RVLM neurons were spontaneously active (2.7 +/- 0.2 spikes per second, n = 69) with 'resting' potential of -54 +/- 0.4 mV (n = 77) and input resistance of 879 +/- 53 M omega (n = 47). Ang II (0.3 to 1 mumol/L) increased the spontaneous firing rate of most bulbospinal neurons (+250%, 28 of 39). In current-clamp mode, Ang II (1 mumol/L) produced depolarization (+6.8 +/- 0.6 mV, n = 59 neurons) and increased input resistance (+21 +/- 2%, n = 36 neurons). In voltage-clamp mode, Ang II elicited an inward current (9.7 +/- 0.9 pA; holding potential, -40 to -55 mV; n = 25 neurons) that reversed polarity at the K+ equilibrium potential (n = 8 neurons) and was barium sensitive (n = 4 neurons). Ang II-evoked conductance change was voltage independent (-40 to -140 mV, n = 8 neurons). The effects of Ang II were blocked by losartan (9 of 9 neurons) but persisted in low Ca2+/high Mg2+ (7 of 7 neurons). Ang II-sensitive cells were inhibited by alpha 2-adrenergic receptor agonists (12 of 15 neurons). Ang II excited 91% (30 of 33) of TH-ir or PNMT-ir cells but 23% (3 of 13) of non-TH-ir neurons. In conclusion, RVLM bulbospinal cells express Ang II type-1 receptors whose activation leads to a reduction in resting K+ conductance.
...
PMID:Angiotensin II decreases a resting K+ conductance in rat bulbospinal neurons of the C1 area. 857 71

Orphanin FQ (OFQ) is a novel heptadecapeptide whose structure resembles that of dynorphin A1-17. Its receptor shares appreciable homology with mu-, delta- and kappa-opioid receptors, and is highly expressed in the hypothalamus. The present study examined the effects of OFQ on neurons within the arcuate nucleus (ARC) of the mediobasal hypothalamus, using intracellular recordings from coronal slices. In current clamp, OFQ produced a hyperpolarization of ARC neurons, including those immunopositive for beta-endorphin, tyrosine hydroxylase and gonadotropin-releasing hormone. This hyperpolarization was dose-dependent, insensitive to antagonism by naloxone and was associated with a decrease in input resistance. In voltage clamp, OFQ produced an outward current associated with an increase in conductance. Varying the extracellular K+ concentration shifted the reversal potential for the OFQ response to the degree predicted by the Nernst equation. Furthermore, barium chloride markedly attenuated both the OFQ-induced hyperpolarization and decrease in input resistance. Administration of maximally effective concentrations of OFQ, followed by coadministration of maximal concentrations of either OFQ and the mu-opioid receptor agonist DAMGO or OFQ and the GABAB receptor agonist baclofen produced additive hyperpolarizations and outward currents. If DAMGO was applied first, followed by the coadministration of DAMGO and OFQ, then the responses were occluded. Taken together, these results indicate that OFQ inhibits beta-endorphin neurons, as well as A12 dopamine and GnRH neurosecretory cells, within the ARC by activating a subset of inwardly-rectifying K+ channels. This suggests that OFQ is not only an antiopioid peptide, but that it also modulates the hypothalamo-pituitary axis and, ultimately, reproductive behavior.
...
PMID:The peptide orphanin FQ inhibits beta-endorphin neurons and neurosecretory cells in the hypothalamic arcuate nucleus by activating an inwardly-rectifying K+ conductance. 950 37

The effects of methionine-enkephalin (ME) on visualized bulbospinal neurons of the rostral ventrolateral medulla (RVL) were characterized in thin slices at 32 degrees C using the whole cell patch-clamp technique. Thirty-five percent of the recorded neurons were found to be tyrosine hydroxylase immunoreactive (C1 neurons). In voltage-clamp recordings, ME (3 microM) induced an outward current in 66% of RVL bulbospinal neurons. A similar percentage of C1 and non-C1 neurons were opioid sensitive. The current induced by ME was inwardly rectifying, reversed close to the potassium equilibrium potential, and was blocked by barium. Most spontaneous postsynaptic currents recorded in these neurons were tetrodotoxin (TTX)-resistant miniature postsynaptic currents (mPSCs). Approximately, 75% of mPSCs had rapid kinetics (decay time = 4.7 ms) and were glutamatergic [miniature excitatory postsynaptic currents (mEPSCs)] because they were blocked by 6-cyano-7-nitroquinoxaline-2,3-dione (10 microM). The remaining mPSCs had much slower kinetics (decay time = 19.6 ms) and were GABAergic [miniature inhibitory postsynaptic currents (mIPSCs)] as they were blocked by gabazine (3 microM) but not by strychnine (3-10 microM). ME decreased the frequency of mEPSCs and mIPSCs by 69 and 43%, respectively. The inhibitory effects of ME were mimicked by the selective mu-opioid receptor agonist endomorphin-1 (EM, 3 microM) and were blocked by naloxone (1 microM). In the absence of TTX, excitatory PSCs evoked by focal electrical stimulation were isolated by application of gabazine and strychnine. EM reduced the amplitude of the evoked EPSCs by 41% without changing their decay time. We conclude that opioids inhibit the majority of RVL C1 and non-C1 bulbospinal neurons by activating a potassium conductance postsynaptically and by decreasing the presynaptic release of glutamate. These cellular mechanisms could explain the depressive cardiovascular effects and the sympathoinhibition produced by opioid transmitters in the RVL, in particular during hypotensive hemorrhage.
...
PMID:Pre- and postsynaptic inhibitory actions of methionine-enkephalin on identified bulbospinal neurons of the rat RVL. 977 56

The rostral ventrolateral medulla (RVLM) controls sympathetic tone via excitatory bulbospinal neurons. It is also the main target of alpha2-adrenoceptor (alpha2-AR) agonists used for treatment of hypertension. In this study, we examined the synaptic mechanisms by which alpha2-AR agonists may inhibit the activity of RVLM bulbospinal neurons. We recorded selectively from RVLM bulbospinal neurons in brain stem slices of neonate rats (P5-P21) using the patch-clamp technique (holding potential -70 mV). alpha2-ARs were activated by norepinephrine (NE, 30 microM) in the presence of the alpha1-adrenoceptor blocker prazosin. NE induced modest outward currents (5-28 pA) in 70% of the cells that were blocked by barium and by the alpha2-AR antagonist 2-methoxyidazoxan. The magnitude of this current was not correlated with the tyrosine hydroxylase immunoreactivity of the neurons. Mono- and oligosynaptic excitatory postsynaptic currents (EPSCs) or monosynaptic inhibitory postsynaptic currents (IPSCs) were evoked by focal electrical stimulation. In all cells, NE decreased the amplitude of the evoked EPSCs in the absence or presence of barium (49 and 70%) and decreased the amplitude of the evoked IPSCs (64 and 59%). The effect of NE on EPSC amplitude was blocked by 2-methoxyidazoxan. Focal stimulation produced a 1- to 2-s EPSC afterdischarge (probably due to activation of interneurons) that was 53% inhibited by NE. In the presence of tetrodotoxin, NE decreased the frequency of miniature EPSCs by 74%. In short, alpha2-AR stimulation produces weak postsynaptic responses in RVLM bulbospinal neurons and powerful presynaptic inhibition of both glutamatergic and GABAergic inputs. Thus the inhibition of RVL bulbospinal neurons by alpha2-AR agonists in vivo results from a combination of postsynaptic inhibition, disfacilitation, and disinhibition.
...
PMID:Alpha2-adrenoceptor-mediated presynaptic inhibition in bulbospinal neurons of rostral ventrolateral medulla. 1048 30

Blood circulation changes in the inner ear play an important role in many physiological and pathological conditions of hearing function. The spiral modiolar artery (SMA) is the terminal artery to the cochlea. It was surrounded with nerve fibers immunostained by an antibody for tyrosine hydroxylase. By using intracellular recording techniques on the acutely isolated SMA, membrane properties of the smooth muscle cells and the neuromuscular transmission in this preparation were investigated. With minimum tension and normal extracellular K(+) concentration (5 mM), the majority of muscle cells showed a resting potential near -80 mV and an input resistance of about 8 MOmega. V/I plot showed an inward rectification in these cells. Barium (50-500 microM) caused strong depolarization and an increase in input resistance. Transmural electrical stimulation evoked stimulation intensity-dependent depolarizations (2-31 mV) following a short latency ( approximately 20 ms). The evoked potential by a low intensity stimulus was completely blocked by 1 microM tetrodotoxin. The potential and a depolarization induced by norepinephrine (10 microM) was usually partially (40-90%) blocked by alpha-receptor antagonists prazosin and/or idazoxan with concentrations up to 1 microM. Action potentials were observed when the depolarization was more than -40 mV. It is concluded that SMA smooth muscle cells, similar to those in other brain small arteries, highly express inward rectifying potassium channels; the cells receive catecholaminergic innervation, and stimulation of the nerves elicited an excitatory junction potential that is partially mediated by adrenergic receptors.
...
PMID:Membrane properties and the excitatory junction potentials in smooth muscle cells of cochlear spiral modiolar artery in guinea pigs. 1057 24

Moxonidine is an antihypertensive drug that lowers sympathetic vasomotor tone by stimulating either alpha2-adrenergic (alpha2-AR) or imidazoline I1 receptors within the rostral ventrolateral medulla (RVL). In this study, we investigated the effects of moxonidine (10 microM) on RVL neurons in brain stem slices of neonatal rats. We recorded mainly from retrogradely labeled RVL bulbospinal neurons (putative presympathetic neurons) except for some extracellular recordings. Prazosin was used to block alpha1-adrenoceptors. Moxonidine inhibited the extracellularly recorded discharges of all spontaneously active RVL neurons tested (bulbospinal and unidentified). This effect was reversed or blocked by the selective alpha2-AR antagonist SKF 86466 (10 microM). In contrast, the I1 imidazoline ligand AGN 192403 (10 microM) had no effect on the spontaneous activity. In whole cell recordings (holding potential -70 mV), moxonidine produced a small and variable outward current (mean 7 pA). This current was observed in both tyrosine hydroxylase-immunoreactive and other bulbospinal neurons and was blocked by SKF 86466. Excitatory postsynaptic currents (EPSCs) evoked by focal electrical stimulation were isolated by incubation with gabazine and strychnine, and inhibitory postsynaptic currents (IPSCs) were isolated with 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX). Moxonidine reduced the amplitude of the evoked EPSCs (EC(50) = 1 microM; 53% inhibition at 10 microM) but not their decay time constant (5.6 ms). The effect of moxonidine on EPSCs persisted in barium (300 microM) and was reduced approximately 80% by SKF 86466. Moxonidine also reduced the amplitude of evoked IPSCs by 63%. In conclusion, moxonidine inhibits putative RVL presympathetic neurons both presynaptically and postsynaptically. All observed effects in the present study are consistent with an alpha2-AR agonist activity of moxonidine.
...
PMID:Prototypical imidazoline-1 receptor ligand moxonidine activates alpha2-adrenoceptors in bulbospinal neurons of the RVL. 1066 92

Cell lines derived from tumors engineered in the CNS offer promise as models of specific neuronal cell types. CAD cells are an unusual subclone of a murine cell line derived from tyrosine hydroxylase (TH) driven tumorigenesis, which undergoes reversible morphological differentiation on serum deprivation. Using single-cell electrophysiology we have examined the properties of ion channels expressed in CAD cells. Despite relatively low resting potentials, CAD cells can be induced to fire robust action potentials when mildly artificially hyperpolarized. Correspondingly, voltage-dependent sodium and potassium currents were elicited under voltage clamp. Sodium currents are TTX sensitive and exhibit conventional activation and inactivation properties. The potassium currents reflected two pharmacologically distinguishable populations of delayed rectifier type channels while no transient A-type channels were observed. Using barium as a charge carrier, we observed an inactivating current that was completely blocked by nimodipine and thus associated with L-type calcium channels. On differentiation, three changes in functional channel expression occurred; a 4-fold decrease in sodium current density, a 1.5-fold increase in potassium current density, and the induction of a small noninactivating barium current component. The neuronal morphology, excitability properties, and changes in channel function with differentiation make CAD cells an attractive model for study of catecholaminergic neurons.
...
PMID:Voltage-dependent ion channels in CAD cells: A catecholaminergic neuronal line that exhibits inducible differentiation. 1111 Aug 18


1

---