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Interhemispheric Modulation on Afferent Sensory Transmission to the Ventral Posterior Medial Thalamus by Contralateral Primary Somatosensory Cortex.

Sung Cherl JUNG ; In Sun CHOI ; Jin Hwa CHO ; Ji Hyun KIM ; Yong Chul BAE ; Maan Gee LEE ; Hyung Cheul SHIN ; Byung Ju CHOI

The Korean Journal of Physiology and Pharmacology.2004;8(3):129-132.

Single unit responses of the ventral posterior medial (VPM) thalamic neurons to stimulation were monitored in anesthetized rats during activation of contralateral primary somatosensory (SI) cortex by GABA antagonist. The temporal changes of afferent sensory transmission were quantitatively analyzed by poststimulus time histogram (PSTH). Mainly, afferent sensory transmission to VPM thalamus was facilitated (15 neurons of total 23) by GABA antagonist (bicuculline) applied to contralateral cortex, while 7 neurons were suppressed. However, when ipsilateral cortex was inactivated by GABA agonist, musimol, there was significant suppression of afferent sensory transmission of VPM thalamus. This suppressed responsiveness by ipsilateral musimol was not affected by bicuculline applied to contralateral cortex. These results suggest that afferent transmission to VPM thalamus may be subjected to the interhemispheric modulation via ipsilateral cortex during inactivation of GABAergic neurons in contralateral SI cortex.
Animals ; Bicuculline ; GABA Agonists ; GABA Antagonists ; GABAergic Neurons ; gamma-Aminobutyric Acid ; Neurons ; Rats ; Somatosensory Cortex* ; Thalamus*

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Physiological, Pharmacological and Toxicological Implications of Heterodimeric Amino Acid Transporters.

Yoshikatsu KANAI ; Hitoshi ENDOU

The Korean Journal of Physiology and Pharmacology.2004;8(3):117-128.

The heterodimeric amino acid transporter family is a subfamily of SLC7 solute transporter family which includes 14-transmembrane cationic amino acid transporters and 12-transmembrane heterodimeric amino acid transporters. The members of heterodimeric amino acid transporter family are linked via a disulfide bond to single membrane spanning glycoproteins such as 4F2hc (4F2 heavy chain) and rBAT (related to b0, +-amino acid transporter). Six members are associated with 4F2hc and one is linked to rBAT. Two additional members were identified as ones associated with unknown heavy chains. The members of heterodimeric amino acid transporter family exhibit diverse substrate selectivity and are expressed in variety of tissues. They play variety of physiological roles including epithelial transport of amino acids as well as the roles to provide cells in general with amino acids for cellular nutrition. The dysfunction or hyperfunction of the members of the heterodimeric amino acid transporter family are involved in some diseases and pathologic conditions. The genetic defects of the renal and intestinal transporters b0, +AT/BAT1 (b0, +-type amino acid transporter/b0, +-type amino acid transporter 1) and y+LAT1 (y+L-type amino acid transporter 1) result in the amino aciduria with sever clinical symptoms such as cystinuria and lysin uric protein intolerance, respectively. LAT1 is proposed to be involved in the progression of malignant tumor. xCT (x-C-type transporter) functions to protect cells against oxidative stress, while its over-function may be damaging neurons leading to the exacerbation of brain damage after brain ischemia. Because of broad substrate selectivity, system L transporters such as LAT1 transport amino acid-related compounds including L-Dopa and function as a drug transporter. System L also interacts with some environmental toxins with amino acid-related structure such as cysteine-conjugated methylmercury. Therefore, these transporter would be candidates for drug targets based on new therapeutic strategies.
Amino Acid Transport Systems* ; Amino Acid Transport Systems, Basic ; Amino Acids ; Brain ; Brain Ischemia ; Cystinuria ; Glycoproteins ; Humans ; Levodopa ; Membranes ; Neurons ; Oxidative Stress

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Multiple Regulation of Roundabout (Robo) Phosphorylation in a Heterologous Cell System.

Hwan Tae PARK

The Korean Journal of Physiology and Pharmacology.2004;8(2):111-115.

Roundabout (Robo) is the transmembrane receptor for slit, the neuronal guidance molecule. In this study, the tyrosine phosphorylation of Robo was observed in Robo-transfected human embryonic kidney cells and developing rat brains, and found to be increased by the treatment with protein kinase A activator, forskolin. In contrast, protein kinase C activation by phorbol-12-myristate-13-acetate decreased the phosphorylation of Robo. Intracellular calcium was required for the tyrosine phosphorylation. Furthermore, the transfection of an Eph receptor tyrosine kinase dramatically enhanced the tyrosine phosphorylation. These findings indicate that the tyrosine phosphorylation of Robo is regulated by multiple mechanisms, and that Eph receptor kinases may play a role in the regulation of tyrosine phosphorylation of Robo in the rat brain.
Animals ; Brain ; Calcium ; Colforsin ; Cyclic AMP-Dependent Protein Kinases ; Humans ; Kidney ; Neurons ; Phosphorylation* ; Phosphotransferases ; Protein Kinase C ; Protein Kinases ; Rats ; Receptor, EphA1 ; Receptors, Eph Family ; Transfection ; Tyrosine

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Heterogeneity of the SR-dependent Inward Na+-Ca2+ Exchange Current in the Heavily Ca2+-buffered Rat Ventricular Myocytes.

Kyung Bong YOON ; Sung Wan AHN ; Chang Mann KO

The Korean Journal of Physiology and Pharmacology.2004;8(2):101-110.

Voltage-sensitive release mechanism was pharmacologically dissected from the Ca2+-induced Ca2+ release in the SR Ca2+ release in the rat ventricular myocytes patch-clamped in a whole-cell mode. SR Ca2+ release process was monitored by using forward-mode Na+-Ca2+ exchange after restriction of the interactions between Ca2+ from SR and Na+-Ca2+ exchange within micro-domains with heavy cytosolic Ca2+ buffering with 10 mM BAPTA. During stimulation every 10 s with a pulse roughly mimicking action potential, the initial outward current gradually turned into a huge inward current of -12.9+/-0.5 pA/pF. From the inward current, two different inward INCXs were identified. One was 10 muM ryanodine-sensitive, constituting 14.2+/-2.3%. It was completely blocked by CdCl2 (0.1 mM and 0.5 mM) and by Na+-depletion. The other was identified by 5 mM NiCl2 after suppression of ICaL and ryanodine receptor, constituting 14.8+/-1.6%. This latter was blocked by either 10 mM caffeine-induced SR Ca2+-depletion or 1 mM tetracaine. IV-relationships illustrated that the latter was activated until the peak in 30~35 mV lower voltages than the former. Overall, it was concluded that the SR Ca2+ release process in the rat ventricular myocytes is mediated by the voltage-sensitive release mechanism in addition to the Ca2+-induced-Ca2+ release.
Action Potentials ; Animals ; Cadmium Chloride ; Cytosol ; Muscle Cells* ; Population Characteristics* ; Rats* ; Ryanodine Receptor Calcium Release Channel ; Tetracaine

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Nitric Oxide-cGMP-Protein Kinase G Pathway Contributes to Cardioprotective Effects of ATP-Sensitive K+ Channels in Rat Hearts.

Dang Van CUONG ; Nari KIM ; Hee Cheol CHO ; Euiyong KIM ; Jin HAN

The Korean Journal of Physiology and Pharmacology.2004;8(2):95-100.

Ischemic preconditioning (IPC) has been accepted as a heart protection phenomenon against ischemia and reperfusion (I/R) injury. The activation of ATP-sensitive potassium (KATP) channels and the release of myocardial nitric oxide (NO) induced by IPC were demonstrated as the triggers or mediators of IPC. A common action mechanism of NO is a direct or indirect increase in tissue cGMP content. Furthermore, cGMP has also been shown to contribute cardiac protective effect to reduce heart I/R-induced infarction. The present investigation tested the hypothesis that KATP channels attenuate DNA strand breaks and oxidative damage in an in vitro model of I/R utilizing rat ventricular myocytes. We estimated DNA strand breaks and oxidative damage by mean of single cell gel electrophoresis with endonuclease III cutting sites (comet assay). In the I/R model, the level of DNA damage increased massively. Preconditioning with a single 5-min anoxia, diazoxide (100muM), SNAP (300muM) and 8- (4-Chlorophenylthio)-guanosine-3', 5'-cyclic monophosphate (8-pCPT-cGMP) (100muM) followed by 15 min reoxygenation reduced DNA damage level against subsequent 30 min anoxia and 60 min reoxygenation. These protective effects were blocked by the concomitant presence of glibenclamide (50muM), 5-hydroxydecanoate (5-HD) (100muM) and 8- (4-Chlorophenylthio)-guanosine-3', 5'-cyclic monophosphate, Rp-isomer (Rp-8-pCPT-cGMP) (100muM). These results suggest that NO-cGMP-protein kinase G (PKG) pathway contributes to cardioprotective effect of KATP channels in rat ventricular myocytes.
Animals ; Anoxia ; Diazoxide ; DNA ; DNA Damage ; Electrophoresis ; Glyburide ; Heart* ; Infarction ; Ischemia ; Ischemic Preconditioning ; KATP Channels ; Muscle Cells ; Nitric Oxide ; Phosphotransferases* ; Potassium ; Rats* ; Reperfusion

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Effects of Central Interleukin-1 on the Cardiovascular Response in Hemorrhaged Rats.

Joon Ho KANG ; Jae Hee JANG ; Dong Kuk AHN ; Jae Sik PARK

The Korean Journal of Physiology and Pharmacology.2004;8(2):89-94.

The arterial pressure is regulated by the nervous and humoral mechanisms. The neuronal regulation is mostly carried out by the autonomic nervous system through the rostral ventrolateral medulla (RVLM), a key area for the cardiovascular regulation, and the humoral regulation is mediated by a number of substances, including the angiotensin (Ang) II and vasopressin. Recent studies suggest that central interleukin-1 (IL-1) activates the sympathetic nervous system and produces hypertension. The present study was undertaken to elucidate whether IL-1 and Ang II interact in the regulation of cardiovascular responses to the stress of hemorrhage. Thus, Sprague-Dawley rats were anesthetized and both femoral arteries were cannulated for direct measurement of arterial pressure and heart rate (HR) and for inducing hemorrhage. A guide cannula was placed into the lateral ventricle for injection of IL-1 (0.1, 1, 10, 20 ng/2mul) or Ang II (600 ng/10mul). A glass microelectrode was inserted into the RVLM to record the single unit spike potential. Barosensitive neurons were identified by an increased number of single unit spikes in RVLM following intravenous injection of nitroprusside. I.c.v. IL-1beta increased mean arterial pressure (MAP) in a dose-dependent fashion, but HR in a dose-independent pattern. The baroreceptor reflex sensitivity was not affected by i.c.v. IL-1beta. Both i.c.v. IL-1alpha and beta produced similar increase in MAP and HR. When hemorrhage was induced after i.c.v. injection of IL-1beta, the magnitude of MAP fall was not different from the control. The IL-1beta group showed a smaller decrease in HR and a lower spike potential count in RVLM than the control. MAP fall in response to hemorrhage after i.c.v. injection of Ang II was not different from the control. When both IL-1 and Ang II were simultaneously injected i.c.v., however, MAP fall was significantly smaller than the control, and HR was increased rather than decreased. These data suggest that IL-1, a defense immune mediator, manifests a hypertensive action in the central nervous system and attenuates the hypotensive response to hemorrhage by interaction with Ang II.
Action Potentials ; Angiotensin II ; Angiotensins ; Animals ; Arterial Pressure ; Autonomic Nervous System ; Baroreflex ; Catheters ; Central Nervous System ; Femoral Artery ; Glass ; Heart Rate ; Hemorrhage ; Hypertension ; Injections, Intravenous ; Interleukin-1* ; Lateral Ventricles ; Microelectrodes ; Neurons ; Nitroprusside ; Rats* ; Rats, Sprague-Dawley ; Sympathetic Nervous System ; Vasopressins

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Effects of Chlorhexidine digluconate on Rotational Rate of n- (9-Anthroyloxy)stearic acid in Model Membranes of Total Lipids Extracted from Porphyromonas gingivalis Outer Membranes.

Hye Ock JANG ; Dong Won KIM ; Byeong Ill KIM ; Hong Gu SIM ; Young Ho LEE ; Jong Hwa LEE ; Jung Ha BAE ; Moon Kyoung BAE ; Tae Hyuk KWON ; Il YUN

The Korean Journal of Physiology and Pharmacology.2004;8(2):83-88.

The purpose of this study was to provide a basis for studying the molecular mechanism of pharmacological action of chlorhexidine digluconate. Large unilamellar vesicles (OPGTL) were prepared with total lipids extracted from cultured Porphyromonas gingivalis outer membranes (OPG). The anthroyloxy probes were located at a graded series of depths inside a membrane, depending on its substitution position (n) in the aliphatic chain. Fluorescence polarization of n- (9-anthroyloxy)stearic acid was used to examine effects of chlorhexidine digluconate on differential rotational mobility, while changing the probes' substitution position (n) in the membrane phospholipids aliphatic chain. Magnitude of the rotational mobility of the intact six membrane components differed depending on the substitution position in the descending order of 16- (9-anthroyloxy)palmitic acid (16-AP), 12, 9, 6, 3 and 2- (9-anthroyloxy)stearic acid (12-AS, 9-AS, 6-AS, 3-AS and 2-AS). Chlorhexidine digluconate increased in a dose-dependent manner the rate of rotational mobility of hydrocarbon interior of the OPGTL prepared with total lipids extracted from cultured OPG, but decreased the mobility of membrane interface of the OPGTL. Disordering or ordering effects of chlorhexidine digluconate on membrane lipids may be responsible for some, but not all of its bacteriostatic and bactericidal actions.
Chlorhexidine* ; Fluorescence Polarization ; Liposomes ; Membrane Lipids ; Membranes* ; Phospholipids ; Porphyromonas gingivalis* ; Porphyromonas* ; Thiram ; Unilamellar Liposomes

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Increase of Synapsin I, Phosphosynapsin (ser-9), and GAP-43 in the Rat Hippocampus after Middle Cerebral Artery Occlusion.

Yeon Joo JUNG ; Pil Woo HUH ; Su Jin PARK ; Jung Sun PARK ; Kyung Eun LEE

The Korean Journal of Physiology and Pharmacology.2004;8(2):77-81.

The loss of neurons and synaptic contacts following cerebral ischemia may lead to a synaptic plastic modification, which may contribute to the functional recovery after a brain lesion. Using synapsin I and GAP-43 as markers, we investigated the neuronal cell death and the synaptic plastic modification in the rat hippocampus of a middle cerebral artery occlusion (MCAO) model. Cresyl violet staining revealed that neuronal cell damage occurred after 2 h of MCAO, which progressed during reperfusion for 2 weeks. The immunoreactivity of synapsin I and GAP-43 was increased in the stratum lucidum in the CA3 subfield as well as in the inner and outer molecular layers of dentate gyrus in the hippocampus at reperfusion for 2 weeks. The immunoreactivity of phosphosynapsin was increased in the stratum lucidum in the CA3 subfield during reperfusion for 1 week. Our data suggest that the increase in the synapsin I and GAP-43 immunoreactivity probably mediates either the functional adaptation of the neurons through reactive synaptogenesis from the pre-existing presynaptic nerve terminals or the structural remodeling of their axonal connections in the areas with ischemic loss of target cells. Furthermore, phosphosynapsin may play some role in the synaptic plastic adaptations before or during reactive synaptogenesis after the MCAO.
Animals ; Axons ; Brain ; Brain Ischemia ; Cell Death ; Dentate Gyrus ; GAP-43 Protein* ; Hippocampus* ; Infarction, Middle Cerebral Artery* ; Middle Cerebral Artery* ; Neurons ; Plastics ; Rats* ; Reperfusion ; Synapsins* ; Viola

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Presynaptic Mechanism Underlying Regulation of Transmitter Release by G Protein Coupled Receptors.

Tomoyuki TAKAHASHI ; Yoshinao KAJIKAWA ; Masahiro KIMURA ; Naoto SAITOH ; Tetsuhiro TSUJIMOTO

The Korean Journal of Physiology and Pharmacology.2004;8(2):69-76.

A variety of G protein coupled receptors (GPCRs) are expressed in the presynaptic terminals of central and peripheral synapses and play regulatory roles in transmitter release. The patch-clamp whole-cell recording technique, applied to the calyx of Held presynaptic terminal in brainstem slices of rodents, has made it possible to directly examine intracellular mechanisms underlying the GPCR-mediated presynaptic inhibition. At the calyx of Held, bath-application of agonists for GPCRs such as GABAB receptors, group III metabotropic glutamate receptors (mGluRs), adenosine A1 receptors, or adrenaline alpha2 receptors, attenuate evoked transmitter release via inhibiting voltage-activated Ca2+ currents without affecting voltage-activated K+ currents or inwardly rectifying K+ currents. Furthermore, inhibition of voltage-activated Ca2+ currents fully explains the magnitude of GPCR-mediated presynaptic inhibition, indicating no essential involvement of exocytotic mechanisms in the downstream of Ca2+ influx. Direct loadings of G protein beta gamma subunit (G beta gamma) into the calyceal terminal mimic and occlude the inhibitory effect of a GPCR agonist on presynaptic Ca2+ currents (IpCa), suggesting that G beta gammamediates presynaptic inhibition by GPCRs. Among presynaptic GPCRs glutamate and adenosine autoreceptors play regulatory roles in transmitter release during early postnatal period when the release probability (p) is high, but these functions are lost concomitantly with a decrease in p during postnatal development.
Adenosine ; Autoreceptors ; Brain Stem ; Epinephrine ; Glutamic Acid ; GTP-Binding Proteins* ; Patch-Clamp Techniques ; Presynaptic Terminals ; Receptor, Adenosine A1 ; Receptors, G-Protein-Coupled* ; Receptors, Metabotropic Glutamate ; Rodentia ; Synapses

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Pharmacokinetics of Dehydroevodiamine Following Intravenous Administration in Rats.

Seong Yun KIM ; Chan Soo MOON ; Yun Sik CHOI ; Sang Bok LEE

The Korean Journal of Physiology and Pharmacology.2004;8(1):65-67.

Dehydroevodiamine (DHED) is one of the bioactive components of the Chinese herbal medicine Wu-chu-yu-tang that has been shown to produce various pharmacological effects. In the present study, we investigated the pharmacokinetics of DHED after intravenous administration of two doses (2.5 and 5 mg/kg) in anesthetized rats. The plasma concentration of DHED was measured by reverse-phase high-performance liquid chromatography with UV detection. The mean area under the curve of the time-concentration profile was 21.9 and 53.9 microgram-min/ml after the 2.5- and 5-mg/kg doses, respectively, and the volume of distribution was 1584.9 and 1580.6 ml following 2.5- and 5-mg/kg doses, respectively. Plasma concentration profiles versus time were compatible with a two-compartment model and first-order kinetics. The terminal elimination half-life was 91.8+/-16.6 min and 78.7+/-11.9 min in the dose of 2.5 and 5 mg/kg, respectively. This is the first report to study the pharmacokinetics of DHED in animals.
Administration, Intravenous* ; Animals ; Asian Continental Ancestry Group ; Chromatography, High Pressure Liquid ; Chromatography, Liquid ; Half-Life ; Herbal Medicine ; Humans ; Injections, Intravenous ; Kinetics ; Pharmacokinetics* ; Plasma ; Rats*

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