• BMB Reports
• /
• v.28 no.5
• /
• pp.382-386
• /
• 1995

One of the reaction pathways in light-invoked signal transduction can be initiated through ion fluxes across the plasma membrane in higher plants. We isolated protoplasts from oat coleoptile and examined the effects of light on the membrane potential using a membrane potential-sensitive fluorescent probe (bisoxonol). Both red and far-red light initially induced a hyperpolarization in oat cells. Red light-induced hyperpolarization was effectively dissipated by 100 mM $K^+$, but the hyperpolarization induced by far-red light was not depolarized by any of the cations ($K^+$, $Ca^{2+}$, $Li^+$, $Na^+$) tested. The depolarization induced by red light and $K^+$ was inhibited by 200 mM TEA, which is a $K^+$ channel blocker. These results suggest that $K^+$ influx through the inward $K^+$ channel may be a depolarization path in the phytochrome-mediated signal transduction.

• Journal of Plant Biology
• /
• v.36 no.4
• /
• pp.383-389
• /
• 1993

The effects of light and $CO_2$ on the electrophysiological characteristics of guard cells in the intact leaf and in the detached epidermis have been investigated. Guard cells in intact leaves showed the membrane hyperpolarization in response to light. The biggest induced change of the membrane potential difference (PD) in the guard cells of the intact leaf was 13 m V by light and 42 mV by $CO_2$ in Commelina communis. Similar results were obtained with Tradescantia virginiana. However, there were no changes of membrane PD in detached epidermis. In order to determine the influence of the mesophyll on the changes of membrane PD, infiltration of the mesophyll cells with photosynthetic inhibitors was performed. In CCCP infiltrated leaf discs the guard cell membrane was depolarized slightly by red-light and hyperpolarized by $CO_2$, but in leaf discs infiltrated with DCCD and DCMU the guard cell membrane was hyperpolrized by both red-light and $CO_2$ as the control leaf discs. In azide infiltrated leaf discs the guard cell membrane showed no response to light and there was a much reduced membrane hyperpolarization by $CO_2$ compared to other responses. It was likely that azide caused leaf damage and the activity of cell metabolism was decreased greatly, resulting in small membrane PD changes by $CO_2$ and no changes by redlight. Therefore, it can be suggested that red light was sensed by the mesophyll and the light induced guard cell membrane hyperpolarization was related to energy produced by cyclic-photophosphorylation, but ${CO_2}-induced$ guard cell membrane hyperpolarization was not related to photosynthesis. Alkalisation of the vacuole was observed when the intact leaf was exposed to $CO_2$, indicating that membrane hyperpolarization was mainly the result of proton efflux.efflux.

• The Korean Journal of Physiology and Pharmacology
• /
• v.9 no.1
• /
• pp.37-43
• /
• 2005

Our previous report demonstrated that chick myoblasts are equipped with $Ca^{2+}$-permeable stretchactivated channels and $Ca^{2+}-activated$ potassium channels ($K_{Ca}$), and that hyperpolarization-induced by $K_{Ca}$ channels provides driving force for $Ca^{2+}$ influx through the stretch-activated channels into the cells. Here, we showed that acetylcholine (ACh) also hyperpolarized the membrane of cultured chick myoblasts, suggesting that nicotinic acetylcholine receptor (nAChR) may be another pathway for $Ca^{2+}$ influx. Under cell-attatched patch configuration, ACh increased the open probability of $K_{Ca}$ channels from 0.007 to 0.055 only when extracellular $Ca^{2+}$ was present. Nicotine, a nAChR agonist, increased the open probability of $K_{Ca}$ channels from 0.008 to 0.023, whereas muscarine failed to do so. Since the activity of $K_{Ca}$ channel is sensitive to intracellular $Ca^{2+}$ level, nAChR seems to be capable of inducing $Ca^{2+}$ influx. Using the $Ca^{2+}$ imaging analysis, we were able to provide direct evidence that ACh induced $Ca^{2+}$ influx from extracellular solution, which was dramatically increased by valinomycin-mediated hyperpolarization. In addition, ACh hyperpolarized the membrane potential from $-12.5{\pm}3$ to $-31.2{\pm}5$ mV by generating the outward current through $K_{Ca}$ channels. These results suggest that activation of nAChR increases $Ca^{2+}$ influx, which activates $K_{Ca}$ channels, thereby hyperpolarizing the membrane potential in chick myoblasts.

• The Korean Journal of Physiology
• /
• v.23 no.1
• /
• pp.35-42
• /
• 1989

The present study was performed to observe the effects of cations on resting membrane potential and pump activity in the unfertilized eggs of ICR strain mice. After an induction of superovulation, the fresh eggs with zona pellucida were collected and the membrane potentials were recorded. Recordings of membrane potential in this study was obtained from the physiological conditions ($37^{\circ}C$ and 4mM Ca in standard solution), differently from the another reports with unphysiological conditions (room temprature and high Ca in standard solution) for a stable and long-lasting observations. Presented data was obtained within 6 hours after collection from the oviduct. The results observed are as follows, 1) Resting potential of the unfertilized eggs was $-25.8{\pm}3.8mV$ $(Mean{\pm}Se,\;n=31)$. 2) As the K ion concentration was increased, resting membrane potential was depolarized but showed hyperpolarization with $K^{+}$ below 25mM. 3) Alteration of the resting membrane potential for the changes of $Na^{+}$ concentration were hardly observed, while resting potential was hyperpolarized as $Ca^{2+}$ concentration was increased. 4) Pump activity as transient or prolonged hyperpolarization was $-2.29{\pm}0.75mV$ $(Mean{\pm}Se,\;n=16)$, the hyperpolarization was increased in both amplitude and duration under the 10mM $Ca^{2+}$ solution. 5) Hyperpolarization due to pump activity was decreased or disappeared by $5{\times}10^{-5}\;M$ ouabain treatment and could not be observed under the both Na-free and Ca-free solutions. 6) Above results are likely to suggest that the resting potential of the mouse unfertilized eggs is affected to mainly by Ca-dependent K conductance and Na-Ca exchange mechanism and that there is pump activity coupling between $K{+}$, $Na^{+}$ and $Ca^{2+}$.

• Korean Journal of Veterinary Research
• /
• v.29 no.3
• /
• pp.245-251
• /
• 1989

In order to manifest the presence of Na-K pump and its property on the unfertilized egg membranes of mouse, membrane potential was recorded under the physiological condition (at $37^{\circ}C$ and 4mM $Ca^{2+}$). After an induction of superovulation, the fresh eggs with zona pellucida were collected from mouse oviduct. Transient hyperpolarization as pump action was recorded after the switch into the high potassium perfusate (15mM $K^+$) from K-free perfusate, and the difference between membrane potential observed just before the perfusion of high potassium solution and the maximal membrane potenlial during the perfusion of high potassium solution was regard as pump activities. The results observed were as follows, 1. Resting mombrane potential was depolarized under the treatment of $10^{-5}M$ ouabain. 2. Pump activities of the unfertilized mouse eggs were $-3.38{\pm}0.61mV$ ($Mean{\pm}SD$, n=6), recorded as transient hyperpolarization due to the electrogenic property. 3. Pump activities were blocked by both treatment of $10^{-5}M$ ouabain and perfusion of Nafree solution, while increased by high $Na^+$ (300mM) perfusion ($-7.45{\pm}0.75mV$, n =2). 4. Hyperpolarization due to pump activity was not altered by $Mn^{2+}$. 5. Above results confirm the presence of ouabain-sensitive Na-K pump, which affected the membrane potential directly, on the unfertilized egg membranes of mouse.

• Journal of Korean Neurosurgical Society
• /
• v.42 no.3
• /
• pp.205-210
• /
• 2007

Objective : Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels mediate the hyperpolarization-activated currents (Ih) that participate in regulating neuronal membrane potential and contribute critically to pacemaker activity, promoting synchronization of neuronal networks. However, distinct regional and cellular localization of HCN channels in the brain have not been precisely defined. Aim of this study was to verify the precise cellular location of HCN1 channels in rat cerebellum to better understand the physiological role these channels play in synaptic transmission between CNS neurons. Methods : HCN1 expression in rat brain was analyzed using immunohistochemistry and electron-microscopic observations. Postsynaptic density-95 (PSD-95), otherwise known as locating and clustering protein, was also examined to clarify its role in the subcellular location of HCN1 channels. In addition, to presume the binding of HCN1 channels with PSD-95, putative binding motifs in these channels were investigated using software-searching method. Results : HCN1 channels were locally distributed at the presynaptic terminal of basket cell and exactly corresponded with the location of PSD-95. Moreover, nine putative SH3 domain of PSD-95 binding motifs were discovered in HCN1 channels from motif analysis. Conclusion : Distinct localization of HCN1 channels in rat cerebellum is possible, especially when analyzed in conjunction with the SH3 domain of PSD-95. Considering that HCN1 channels contribute to spontaneous rhythmic action potentials, it is suggested that HCN1 channels located at the presynaptic terminal of neurons may play an important role in synaptic plasticity.

• The Korean Journal of Physiology and Pharmacology
• /
• v.5 no.5
• /
• pp.373-380
• /
• 2001

The action of opioid on the hyperpolarization-activated cation current $(I_h)$ in substantia gelatinosa neurons were investigated by using whole-cell voltage-clamp recording in rat spinal brain slices. Hyperpolarizing voltage steps revealed slowly activating currents in a subgroup of neurons. The half-maximal activation and the reversal potential of the current were compatible to neuronal $I_h.$ DAMGO $(1\;{\mu}M),$ a selective- opioid agonist, reduced the amplitude of $I_h$ reversibly. This reduction was dose-dependent and was blocked by CTOP $(2\;{\mu}M),$ a selective ${\mu}-opioid$ antagonist. DAMGO shifted the voltage dependence of activation to more hyperpolarized potential. Cesium (1 mM) or ZD 7288 $(100\;{\mu}M)$ blocked $I_h$ and the currents inhibited by cesium, ZD 7288 and DAMGO shared a similar time and voltage dependence. These results suggest that activation of ${\mu}-opioid$ receptor by DAMGO can inhibit $I_h$ in a subgroup of rat substantia gelatinosa neurons.

• Journal of Microbiology and Biotechnology
• /
• v.13 no.6
• /
• pp.833-840
• /
• 2003

Sperm motility of salmonid fishes is suppressed by external $K^{+}$ and initiated by decrease of $K^{+}$ concentration surrounding the sperm. It was shown that the decrease in external $K^{+}$ concentration induced not only the initiation of sperm motility, but also hyperpolarization of the plasma membrane and synthesis of cAMP in the sperm of rainbow trout, steelhead trout, and masu salmon. Inhibitors of $K^{+}$ channels, especially voltage-dependent $K^{+}$ channels, inhibited these three reactions, and the inhibitions were abolished by subsequent addition of a $K^{+}$ ionophore, valinomycin, suggesting that $K^{+}$ efflux through the $K^{+}$ channel contributes to rapid changes in the membrane potential of sperm and cAMP synthesis, thereby resulting in the initiation of sperm motility of salmonid fishes.

• Journal of the Korean Magnetic Resonance Society
• /
• v.21 no.4
• /
• pp.126-130
• /
• 2017

In the developed NMR hyperpolarization techniques, Parahydrogen-Induced Polarization (PHIP) technique is widely utilized to overcome the low sensitivity of the NMR/MRI. Parahydrogen generator is essential to produce high spin order of parahydrogen molecule. Commercial parahydrogen generator is well developed with user-friendly systems. However, it has drawbacks of long preparation time (~ 2h including cooling down time of 1h) and high cost (~ 200 million won) for the commercial setup. We designed a simple and portable parahydrogen generating system with low cost (~ 2 million won), which produce polarization in less than 1 min. With the designed parahydrogen generator, we successfully performed the PHIP with Wilkinson's catalyst on styrene. This study will broaden the parahydrogen based polarization transfer study on many researchers by providing the simple portable and low cost parahydrogen generator.

• International Journal of Oral Biology
• /
• v.34 no.4
• /
• pp.191-197
• /
• 2009

Somatostatin (SST) is a known neuromodulator of the central nervous system. The substantia gelatinosa (SG) of the trigeminal subnucleus caudalis (Vc) receives many thinmyelinated $A{\delta}$-fiber and unmyelinated C primary afferent fibers and is involved in nociceptive processing. Many studies have demonstrated that SST plays a pivotal role in pain modulation in the spinal cord. However, little is yet known about the direct effects of SST on the SG neurons of the Vc in adult mice. In our present study, we investigated the direct membrane effects of SST and a type 2 SST receptor agonist, seglitide (SEG), on the SG neurons of the Vc using a gramicidin-perforated current clamp in adult mice. The majority (53%, n = 27/51) of the adult SG neurons were hyperpolarized by SST (300 nM) but no differences were found in the hyperpolarization response rate between males and females. When SST was applied successively, the second response was smaller ($76{\pm}9.5%$, n=19), suggesting that SST receptors are desensitized by repeated application. SST-induced hyperpolarization was also maintained under conditions where presynaptic events were blocked ($75{\pm}1.0%$, n=5), suggesting that this neuromodulator exerts direct effects upon postsynaptic SG neurons. SEG was further found to induce membrane hyperpolarization of the SG neurons of the Vc. These results collectively demonstrate that SST inhibits the SG neuronal activities of the Vc in adult mice with no gender bias, and that these effects are mediated via a type 2 SST receptor, suggesting that this is a potential target for orofacial pain modulation.