Mechanosensitivity of voltage-gated K⁺ currents in rat trigeminal ganglion neurons

Piao, Lin,Ying Li, Hai,Park, Chul-Kyu,Cho, Ik-Hyun,Piao, Zheng Gen,Jung, Sung Jun,Choi, Se-Young,Lee, Sung Joong,Park, Kyungpyo,Kim, Joong-Soo,Oh, Seog Bae Wiley Subscription Services, Inc., A Wiley Company 2006 JOURNAL OF NEUROSCIENCE RESEARCH - Vol.83 No.7

<P>We investigated the mechanosensitivity of voltage-gated K<SUP>+</SUP> channel (VGPC) currents by using whole-cell patch clamp recording in rat trigeminal ganglion (TG) neurons. On the basis of biophysical and pharmacological properties, two types of VGPC currents were isolated. One was transient (I<SUB>K,A</SUB>), the other sustained (I<SUB>K,V</SUB>). Hypotonic stimulation (200 mOsm) markedly increased both I<SUB>K,A</SUB> and I<SUB>K,V</SUB> without affecting their activation and inactivation kinetics. Gadolinium, a well-known blocker of mechanosensitive channels, failed to block the enhancement of I<SUB>K,A</SUB> and I<SUB>K,V</SUB> induced by hypotonic stimulation. During hypotonic stimulation, cytochalasin D, an actin-based cytoskeletal disruptor, further increased I<SUB>K,A</SUB> and I<SUB>K,V</SUB>, whereas phalloidin, an actin-based cytoskeletal stabilizer, reduced I<SUB>K,A</SUB> and I<SUB>K,V</SUB>. Confocal imaging with Texas red-phalloidin showed that actin-based cytoskeleton was disrupted by hypotonic stimulation, which was similar to the effect of cytochalasin D. Our results suggest that both I<SUB>K,A</SUB> and I<SUB>K,V</SUB> are mechanosensitive and that actin-based cytoskeleton is likely to regulate the mechanosensitivity of VGPC currents in TG neurons. © 2006 Wiley-Liss, Inc.</P>

Characterization of Intermediate Conductance K<SUP>⁢</SUP> Channels in Submandibular Gland Acinar Cells

Sung-Man Cho,Zheng Gen Piao,Yoon Bae Kim,Joong-Soo Kim,Kyungpyo Park 대한생리학회-대한약리학회 2002 The Korean Journal of Physiology & Pharmacology Vol.6 No.6

<P> There are some evidences that K<SUP>⁢</SUP> efflux evoked by muscarinic stimulation is not mainly mediated by large conductance K<SUP>⁢</SUP> (BK) channels in salivary gland. In this experiment, we therefore characterised non BK channels in rat submandibular gland acinar cells and examined the possibility of agonist effect on this channel using a patch clamp technique. Two types of K<SUP>⁢</SUP> channels were observed in these cells. BK channels were observed in 3 cells from total 6 cells and its average conductance was 152⁑7 pS (n=3). The conductance of the another types of K<SUP>⁢</SUP> channel was estimated as 71⁑7 pS (n=6). On the basis of the conductance of this channel, we defined this channel as intermediate conductance K<SUP>⁢ </SUP>(IK) channels, which were observed from all 6 cells we studied. When we increased Ca<SUP>2⁢</SUP> concentration of the bath solution in inside-out mode, the IK channel activity was greatly increased, suggesting this channel is Ca<SUP>2⁢</SUP> sensitive. We next examined the effect of carbachol (CCh) and isoproterenol on the activity of the IK channels. 10<SUP>⁣5 </SUP>M isoproterenol significantly increased the open probability (Po) from 0.08⁑0.02 to 0.21⁑0.03 (n=4, P<0.05). Application of 10<SUP>⁣5 </SUP>M CCh also increased Po from 0.048⁑0.03 to 0.55⁑0.33 (n=5, P<0.05) at the maximum channel activity. The degree of BK channel activation induced by the same concentration of CCh was lower than that of IK channels; Po value was 0.011⁑0.003 and 0.027⁑0.005 in control and during CCh stimulation (n=3), respectively. The result suggests that IK channels exist in salivary acinar cells and its channel activity is regulated by muscaricinic and β- adrenergic agonist. We conclude that IK channels also play a putative role in secretion as well as the BK channels in rat submandibular gland acinar cells.

Changes in Expression of High Voltage-Activated Calcium Channel in Facial Motoneurons Following Facial Nerve Injury

Bang, Geug-Young,Piao, Zheng Gen,Choi, Se-Young,Lee, Sung Joong,Park, Kyungpyo,Kim, Joong Soo,Oh, Seog Bae Korean Academy of Oral Biology and the UCLA Dental 2004 International Journal of Oral Biology Vol.29 No.4

Peripheral nerve injury is known to cause plastic changes in soma as well as degenerative changes in terminal axons. In the present study, we examined whether facial nerve injury induces changes in expression of calcium channels in rat facial motoneurons. Facial motor nucleus was located by retrograde tracing with a fluorecent dye DiI applied into proximal end of axotomized facial nerve. Immunohistochemistry and RT-PCR analysis were performed to examine changes in calcium channel expression in facial motoneurons 3 days, 1 week and 2 weeks after peripheral facial nerve transection at the entry of stylomastoid foramen. We found that α_(1A), α_(1B), α_(1C) and α_(1E) subunits, which form P/Q-, N-, L-, and R-type Ca^(2+) channels respectively, are constitutively present in uninjured normal facial motoneurons. Whereas the intensity of α_(1B) and α_(1C) subunit immunostaining was reduced in axotomized facial motoneurons, the alterations of α_(1A) and α_(1E) subunit expression were not observed following facial nerve axolomy. RT-PCR analysis also confirmed the constitutive expression of P/Q-, L-, N- and R-type Ca^(2+) channels in normal facial motonuerons, and down-regulation of a,B and aw subunit mRNA in axotomized facial motoneurons. These results suggest that changes of calcium channel expression in facial motoneurons may reflect the degenerative process of soma following axotomy.

GABAergic Synaptic Input to Mesencephalic Trigeminal Neurons in Rat

Ryu, Hyo-Chel,Piao, Zheng Gen,Choi, Se-Young,Lee, Sung Joong,Park, Kyungpyo,Kim, Joong Soo,Oh, Seog Bae Korean Academy of Oral Biology and the UCLA Dental 2005 International Journal of Oral Biology Vol.30 No.2

The mesencephalic trigeminal nucleus (Mes V) contains cell bodies of primary afferent sensory neurons that relay proprioceptive information from the periodontium and masticatory muscles and function as typical sensory neurons or potentially as integrative interneurons. In the present study, we studied these two potential functions using combined experimental approaches of retrograde labeling and whole cell patch clamp recording. Mes V neurons that presumably originate from periodontal nerve fibers in subsets of Mes V nucleus were identified by retrograde labeling with a fluorescent dye, DiI, which was applied onto inferior alveolar nerve. These cells were elliptical perikarya shaped cells about 40 μm in diameter. In these neurons, we measured high voltage-activated calcium channel (HVACC) currents. GABA_(B) agonist, baclofen, inhibited calcium currents, and the HVACC currents inhibition by baclofen was voltage-dependent, exhibited prepulse facilitation, indicating that it was mediated by G_(i)/G_(o) protein. Taken together, our results demonstrate that Mes V neurons not only have cell bodies originating from periodontium, but also receive synaptic inputs including GABAergic neurons suggesting that Mes V neurons function as both primary sensory neurons and integrative interneurons.

Ca2+-activated K+ Currents of Pancreatic Duct Cells in Guinea-pig

이한욱,Jingchao Li,구나연,Zheng Gen Piao,황성민,한재웅,최한샘,이종흔,김중수,박경표 대한약리학회 2004 The Korean Journal of Physiology & Pharmacology Vol.8 No.6

There are numerous studies on transepithelial transports in duct cells including Cl- and/or HCO3-. However, studies on transepithelial K+ transport of normal duct cells in exocrine glands are scarce. In the present study, we examined the characteristics of K+ currents in single duct cells isolated from guinea pig pancreas, using a whole-cell patch clamp technique. Both Cl- and K+ conductance were found with KCl rich pipette solutions. When the bath solution was changed to low Cl-, reversal potentials shifted to the negative side, -75±4 mV, suggesting that this current is dominantly selective to K+. We then characterized this outward rectifying K+ current and examined its Ca2+ dependency. The K+ currents were activated by intracellular Ca2+. 100 nM or 500 nM Ca2+ in pipette significantly (P<0.05) increased outward currents (currents were normalized, 76.8±7.9 pA, n=4 or 107.9±35.5 pA, n=6) at +100 mV membrane potential, compared to those with 0 nM Ca2+ in pipette (27.8±3.7 pA, n=6). We next examined whether this K+ current, recorded with 100 nM Ca2+ in pipette, was inhibited by various inhibitors, including Ba2+, TEA and iberiotoxin. The currents were inhibited by 40.4±% (n=3), 87.0±% (n=5) and 82.5±% (n=9) by 1 mM Ba2+, 5 mM TEA and 100 nM iberiotoxin, respectively. Particularly, an almost complete inhibition of the current by 100 nM iberiotoxin further confirmed that this current was activated by intracellular Ca2+. The K+ current may play a role in secretory process, since recycling of K+ is critical for the initiation and sustaining of Cl- or HCO3- secretion in these cells.

Characterization of Intermediate Conductance $K^+$ Channels in Submandibular Gland Acinar Cells

Cho, Sung-Man,Piao, Zheng-Gen,Kim, Yoon-Bae,Kim, Joong-Soo,Park, Kyung-Pyo The Korean Society of Pharmacology 2002 The Korean Journal of Physiology & Pharmacology Vol.6 No.6

There are some evidences that $K^+$ efflux evoked by muscarinic stimulation is not mainly mediated by large conductance $K^+$ (BK) channels in salivary gland. In this experiment, we therefore characterised non BK channels in rat submandibular gland acinar cells and examined the possibility of agonist effect on this channel using a patch clamp technique. Two types of $K^+$ channels were observed in these cells. BK channels were observed in 3 cells from total 6 cells and its average conductance was $152{\pm}7$ pS (n=3). The conductance of the another types of $K^+$ channel was estimated as $71{\pm}7$ pS (n=6). On the basis of the conductance of this channel, we defined this channel as intermediate conductance $K^+$ (IK) channels, which were observed from all 6 cells we studied. When we increased $Ca^{2+}$ concentration of the bath solution in inside-out mode, the IK channel activity was greatly increased, suggesting this channel is $Ca^{2+}$ sensitive. We next examined the effect of carbachol (CCh) and isoproterenol on the activity of the IK channels. $10^{-5}$ M isoproterenol significantly increased the open probability (Po) from $0.08{\pm}0.02$ to $0.21{\pm}0.03$ (n=4, P<0.05). Application of $10^{-5}$ M CCh also increased Po from $0.048{\pm}0.03$ to $0.55{\pm}0.33$ (n=5, P<0.05) at the maximum channel activity. The degree of BK channel activation induced by the same concentration of CCh was lower than that of IK channels; Po value was $0.011{\pm}0.003$ and $0.027{\pm}0.005$ in control and during CCh stimulation (n=3), respectively. The result suggests that IK channels exist in salivary acinar cells and its channel activity is regulated by muscaricinic and ${\beta}-adrenergic$ agonist. We conclude that IK channels also play a putative role in secretion as well as the BK channels in rat submandibular gland acinar cells.

Ca<SUP>2⁢</SUP>-activated K<SUP>⁢</SUP> Currents of Pancreatic Duct Cells in Guinea-pig

Han-Wook Lee,Jingchao Li,Na-Youn Koo,Zheng Gen Piao,Sung Min Hwang,Jae-Woong Han,Han-Saem Choi,Jong-Heun Lee,Joong Soo Kim,Kyungpyo Park 대한생리학회-대한약리학회 2004 The Korean Journal of Physiology & Pharmacology Vol.8 No.6

There are numerous studies on transepithelial transports in duct cells including Cl<SUP>⁣</SUP> and/or HCO<SUB>3</SUB><SUP>⁣</SUP>. However, studies on transepithelial K<SUP>⁢</SUP> transport of normal duct cells in exocrine glands are scarce. In the present study, we examined the characteristics of K<SUP>⁢</SUP> currents in single duct cells isolated from guinea pig pancreas, using a whole-cell patch clamp technique. Both Cl<SUP>⁣</SUP> and K<SUP>⁢</SUP> conductance were found with KCl rich pipette solutions. When the bath solution was changed to low Cl<SUP>⁣</SUP>, reversal potentials shifted to the negative side, ⁣75⁑4 mV, suggesting that this current is dominantly selective to K<SUP>⁢</SUP>. We then characterized this outward rectifying K<SUP>⁢</SUP> current and examined its Ca<SUP>2⁢</SUP> dependency. The K<SUP>⁢</SUP> currents were activated by intracellular Ca<SUP>2⁢</SUP>. 100 nM or 500 nM Ca<SUP>2⁢</SUP> in pipette significantly (P<0.05) increased outward currents (currents were normalized, 76.8⁑7.9 pA, n=4 or 107.9⁑35.5 pA, n=6) at ⁢100 mV membrane potential, compared to those with 0 nM Ca<SUP>2⁢</SUP> in pipette (27.8⁑3.7 pA, n=6). We next examined whether this K<SUP>⁢</SUP> current, recorded with 100 nM Ca<SUP>2⁢</SUP> in pipette, was inhibited by various inhibitors, including Ba<SUP>2⁢</SUP>, TEA and iberiotoxin. The currents were inhibited by 40.4⁑% (n=3), 87.0⁑% (n=5) and 82.5⁑% (n=9) by 1 mM Ba<SUP>2⁢</SUP>, 5 mM TEA and 100 nM iberiotoxin, respectively. Particularly, an almost complete inhibition of the current by 100 nM iberiotoxin further confirmed that this current was activated by intracellular Ca<SUP>2⁢</SUP>. The K<SUP>⁢</SUP> current may play a role in secretory process, since recycling of K<SUP>⁢</SUP> is critical for the initiation and sustaining of Cl<SUP>⁣</SUP> or HCO<SUB>3</SUB><SUP>⁣</SUP> secretion in these cells.

[$Ca^{2+}-activated\;K^+$ Currents of Pancreatic Duct Cells in Guinea-pig

Lee, Han-Wook,Li, Jing Chao,Koo, Na-Youn,Piao, Zheng Gen,Hwang, Sung-Min,Han, Jae-Woong,Choi, Han-Saem,Lee, Jong-Heun,Kim, Joong-Soo,Park, Kyung-Pyo The Korean Society of Pharmacology 2004 The Korean Journal of Physiology & Pharmacology Vol.8 No.6

There are numerous studies on transepithelial transports in duct cells including $Cl^-$ and/or $HCO_3^-$. However, studies on transepithelial $K^+$ transport of normal duct cells in exocrine glands are scarce. In the present study, we examined the characteristics of $K^+$ currents in single duct cells isolated from guinea pig pancreas, using a whole-cell patch clamp technique. Both $Cl^-$ and $K^+$ conductance were found with KCI rich pipette solutions. When the bath solution was changed to low $Cl^-$, reversal potentials shifted to the negative side, $-75{\pm}4\;mV$, suggesting that this current is dominantly selective to $K^+$. We then characterized this outward rectifying $K^+$ current and examined its $Ca^{2+}$ dependency. The $K^+$ currents were activated by intracellular $Ca^{2+}$. 100 nM or 500 nM $Ca^{2+}$ in pipette significantly (P<0.05) increased outward currents (currents were normalized, $76.8{\pm}7.9\;pA$, n=4 or $107.9{\pm}35.5\;pA$, n=6) at +100 mV membrane potential, compared to those with 0 nM $Ca^{2+}$ in pipette $(27.8{\pm}3.7\;pA,\;n=6)$. We next examined whether this $K^+$ current, recorded with 100 nM $Ca^{2+}$ in pipette, was inhibited by various inhibitors, including $Ba^{2+}$, TEA and iberiotoxin. The currents were inhibited by $40.4{\pm}%$ (n=3), $87.0{\pm}%$ (n=5) and $82.5{\pm}%$ (n=9) by 1 mM $Ba^{2+}$, 5 mM TEA and 100 nM iberiotoxin, respectively. Particularly, an almost complete inhibition of the current by 100 nM iberiotoxin further confirmed that this current was activated by intracellular $Ca^{2+}$. The $K^+$ current may play a role in secretory process, slnce recycling of $K^+$ is critical for the initiation and sustaining of $CI^-$ or $HCO_3^-$ secretion in these cells.