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Voltage-gated K+ channels in chemoreceptor sensory neurons of rat petrosal ganglion
Brain Research 897 (2001) 199–203 www.elsevier.com / locate / bres
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Voltage-gated K 1 channels in chemoreceptor sensory neurons of rat petrosal ganglion Ellen M. Andrews, Diana L. Kunze* Rammelkamp Center for Education and Research, MetroHealth Medical System and Department of Neurosciences, Case Western Reserve University, 2500 MetroHealth Drive, Cleveland, OH 44109 -1998, USA Accepted 9 January 2001
Abstract A subpopulation of sensory neurons in the petrosal ganglion transmits information between peripheral chemoreceptors (glomus cells) in the carotid body and relay neurons in the nucleus of the solitary tract. Expression of voltage-gated K 1 channels in these neurons was characterized by immunohistochemical localization. Five members of the Kv1 family, Kv1.1, Kv1.2, Kv1.4, Kv1.5 and Kv1.6 and members of two other families, Kv2.1 and Kv4.3, were identified in over 90% of the chemoreceptor neurons. Although the presence of these channel proteins was consistent throughout the population, individual neurons showed considerable variation in K 1 current profiles. 2001 Published by Elsevier Science B.V. Theme: Endocrine and autonomic regulation Topic: Respiratory regulation Keywords: Petrosal; Chemoreceptor; K 1 channel
The transmission of the signal from the chemoreceptors in the carotid body to the nucleus of the solitary tract is dependent on the voltage-gated K 1 (Kv) channels. While there is a substantial body of electrophysiological studies characterizing Kv channels in the chemoreceptor type 1 glomus cells [4], there is relatively little information on the sensory neurons they activate. A large number of distinct Kv channels have been cloned and characterized. Each has unique characteristics that may influence the neuronal activity in a different way. Our objective was to identify the Kv channels expressed in the population of petrosal neurons that are part of the peripheral chemoreceptor reflex pathway. These neurons were identified either by anterograde labeling from the carotid body or by the presence of immunoreactivity to the enzyme, tyrosine hydroxylase, TH [6]. Sprague–Dawley rats (2–3 weeks) were anesthetized with a cocktail of 0.1 ml ketamine HCl (100 mg / ml), 0.1 ml xylazine (20 mg / ml), and 0.2 ml acepromazine maleate *Corresponding author. Tel.: 11-216-778-8967; fax: 11-216-7782090. E-mail address: [email protected] (D.L. Kunze).
(10 mg / ml) at 1.2 ml / kg. The left carotid bifurcation was exposed and the carotid body isolated. Crystals of CM-DiI or DiI 291 (Molecular Probes) were placed on the carotid body and covered with Kwik-Sil (World Precision Instruments). After the Kwik-Sil hardened, the incision was sutured and the animal allowed to recover. A minimum of 3 days later the animal was sacrificed and the ganglion removed. The carotid body and the carotid sinus were examined to insure that the dye had remained confined to the carotid body region. For the immunohistochemistry studies, 16 labeled animals were anesthetized with halothane and decapitated. The petrosal ganglia were removed, frozen and serial 16 mm cryostat sections were fixed 15–20 min in 4% paraformaldehyde, 0.1 M lysine, 0.1 M sodium periodate, pH 6.2 and 0.1% Triton-X. Sections were rinsed and incubated with blocking solution (phosphate-buffered saline (PBS), 3% normal goat serum, 3% normal donkey serum, and 1% bovine serum albumin) for 30 min. All antibodies were diluted in blocking solution. Sections were incubated in primary antibodies 3 h at room temperature. The slides were rinsed in PBS and secondary antibodies were added for 90 min. Controls sections were incubated with PBS and appropriate sec-
0006-8993 / 01 / $ – see front matter 2001 Published by Elsevier Science B.V. PII: S0006-8993( 01 )02121-7
E.M. Andrews, D.L. Kunze / Brain Research 897 (2001) 199 – 203
200
Table 1 This table provides the number and percentage of neurons for which specific Kv channel antibodies co-localize with the TH antibody or with the CM-DiI labeled neurons Kv channel
Number of cells with both Kv and CM-DiI
Total number of CM-DiI cells
Percentage of co-localization
Number of cells with both Kv and TH
Total number of TH cells
Percentage of co-localization
mKv1.1 rKv1.2 mKv1.4 mKv1.5 rKv2.1 rKv4.3
142 195 172 154 95 82
146 198 172 158 102 85
97.3 98.5 100.0 97.5 93.0 96.5
69 114 221 109 111 147
69 129 229 133 115 159
100.0 89.0 96.5 94.2 96.5 92.4
ondary antibodies. Sections were rinsed, mounted in Vectashield (Vector Laboratories) with DAPI and viewed using an Olympus BH-2 fluorescent microscope. Individual cells were counted through successive sections by following the labeled nuclei. Each K 1 channel was studied in ganglia from two animals except where Kv1.1 was co-localized with TH, n51. The following commercial antibodies were used: anti-TH (Affinity BioReagents and DiaSorin), anti-Kv1.1 and anti-Kv1.4 (Upstate Biotechnology), anti-Kv1.5 (Transduction Laboratories), anti-Kv1.2, anti-Kv1.6 and anti-Kv4.3 (Alamone Labs) and antiKv2.1(Upstate Biotechnology). Secondary antibodies were obtained from Jackson ImmunoResearch Laboratories. For electrophysiological studies, petrosal ganglia were excised from rats in which the carotid body had been labeled. The ganglia were collected after halothane anesthesia followed by decapitation and incubated in Earle’s balanced saline solution (EBSS, Gibco BRL) containing 1 mg / ml collagenase 1 h at 378C. The enzyme-containing medium was replaced with 3 ml of Dulbecco’s modified Eagle’s medium / F-12 with 5% fetal bovine serum, 0.1% serum extender (Collaborative Research), 1% penicillin / streptomycin and 1.5 mg / ml albumin. The cells were dispersed and plated onto glass coverslips. K 1 currents were recorded using the patch technique for whole-cell recording, 4–24 h after plating. Data were digitized and analyzed using pClamp programs (Axon Instruments). The extracellular solution contained (in mM): 137 NMDG (N-methylD-glucamine), 5.4 KCl, 1 MgCl 2 , 0.02 CaCl 2 , 10 Glucose, 10 HEPES, pH 7.3 with KOH; the pipette solution contained (in mM) 145 K-aspartate, 1.95 CaCl 2 , 2.2 EGTA [ethylene-glycol-bis(b-amino ethylether)-N,N9tetra-acetic acid], 2 MgCl 2 , 10 Glucose, and 5 HEPES, pH 7.3 with KOH. Expression of Kv1.1, Kv1.2, Kv1.4, Kv1.5, Kv1.6, Kv2.1 and Kv4.3 was observed in petrosal neurons whose afferent terminals project from the carotid body by co-
localization with CM DiI (Table 1 and Fig. 1) or by the presence of TH. With the exception of a slightly smaller percentage of Kv1.2 in TH-containing cells (89%), the presence of these Kv channels was .92% in both THcontaining neurons and those labeled with CM-DiI. Since a small population of TH-immunoreactive petrosal neurons do not project to the carotid body [6], some TH-containing cells may signal other modalities. The level of expression as indicated by the intensity of the fluorescence was variable within the population. The staining was, for the most part, cytoplasmic with some perinuclear localization. The label appears to extend to the plasma membrane but at the light microscopic level it is difficult to localize the protein to the membrane itself. The variability in the level of staining among neurons suggested non-uniformity in the somal K 1 currents. K 1 currents were recorded from primary cultures of DiI 291labeled petrosal neurons. Representative examples of current profiles from 3 / 18 neurons from three animals were selected to show the variability within this population of sensory neurons. The most obvious difference among neurons was the amplitude of an early transient phase. This was pronounced in a rare large neuron (90 pF) that showed an initial large transient component that decays to a steady current (Fig. 2A). The voltage-dependence of inactivation of the transient phase following 1 s prepulses shows the transient phase inactivated between 2110 and 260 mV. This is in contrast to a second neuron (44 pF) in which the transient phase is small compared to the slowly developing steady-state current (Fig. 2B). In this neuron the voltagedependence of inactivation occurred at more depolarized potentials. In the third neuron, a small cell (33 pF), the transient phase was not evident in the whole-cell currents in response to voltage steps or during the inactivation protocol (Fig. 2C). The steady-state currents also show differences in the voltage-dependence of activation. In summary, immunoreactivity for Kv1.1, Kv1.2, Kv1.4,
Fig. 1. (A–D) Photomicrographs of chemoreceptor neurons in the petrosal ganglion double-stained for tyrosine hydroxylase (TH) using a rhodamineconjugated (red; A, D) or FITC-labeled (green; B, C) secondary antibodies and antibodies for voltage-gated K 1 channels (Kv) using rhodamine-conjugated (red; B, C) or FITC-labeled (green; A, D) secondary antibodies: (A) Kv1.1; (B) Kv1.6; (C) Kv4.3; and (D) Kv1.5. (E–H) Photomicrographs of sensory neurons in the petrosal ganglion labeled with CM DiI which is seen as yellow / orange particles within the neurons. The sections were stained for presence of antibodies against Kv channels: (E) Kv1.2; (F) Kv1.4; (G) Kv2.1; and (H) Kv1.5, using FITC-labeled secondary antibodies (green). Arrows indicate examples of co-localization (yellow / orange). Nuclei are stained with DAPI (blue). Scale bar550 mm.
E.M. Andrews, D.L. Kunze / Brain Research 897 (2001) 199 – 203
201
202
E.M. Andrews, D.L. Kunze / Brain Research 897 (2001) 199 – 203
Fig. 2. Examples of diversity in K 1 currents recorded from three chemoreceptor neurons. (A–C) Left panel illustrates the current response to 300 ms depolarizing steps from 270 mV to 140 mV in 10 mV increments from a holding potential of 290 mV. The middle panel illustrates the current –voltage relationships of the peak of the transient current at the beginning of the pulse (A and B) and the steady-state currents taken at the end of the pulse (A, B and C). The right panel gives the voltage dependence of inactivation for the peak of the transient current at the beginning of the pulse (A, B) or for (C), the steady current. Examples of the current used to obtain this curve are given in the inset. The currents were obtained during a step to 20 mV from 1 s prepulses of 2110 to 210 mV. The range of prepulses selected for the inset is indicated for each cell. Capacitance of neurons in A–C, 90 pF, 44 pF and 33 pF, respectively.
Kv1.5, Kv1.6, Kv2.1 and Kv4.3 was present but not of uniform intensity in the chemoreceptor cells of the petrosal ganglion. It is not surprising that the K 1 channel expression levels may differ since these neurons are not a homogenous population with regard to neurotransmitter content or sodium channel composition. Clearly there is also a difference in potassium channel profiles. A previous study that reported there were no obvious transient K 1 currents in rat petrosal neurons [9]. This would be consistent with our results if the K 1 currents we recorded in the small cells were representative of the unmyelinated population that Donnelly [3] recently reported represents most of the chemoreceptor cells in the rat. Strategies for isolating the specific currents, such as selective toxins,
introduction of antisense constructs or blocking antibodies, will be needed to associate individual Kv a subunits with specific components of the current. Interestingly, several of the K 1 channels reported here have been shown to modified by hypoxia [1,2,5,7,8,10]. Modulation of K 1 channel activity by hypoxia in the chemoreceptor reflex pathways beyond the glomus cell should be explored.
Acknowledgements The authors wish to thank Pat Glazebrook for her technical advice. This work was supported by PHHS grant HL25830.
E.M. Andrews, D.L. Kunze / Brain Research 897 (2001) 199 – 203
References [1] S.L. Archer, E. Souil, A.T. Dinh-Xuan, B. Schremmer, J.C. Mercier, A. El Yaagoubi, L. Nguyen-Huu, H.L. Reeve, V. Hampl, Molecular identification of the role of voltage-gated K 1 channels, Kv1.5 and Kv2.1, in hypoxic pulmonary vasoconstriction and control of resting membrane potential in rat pulmonary artery myocytes, J. Clin. Invest. 101 (1998) 2319–2330. [2] L. Conforti, I. Bodi, J.W. Nisbet, D.E. Millhorn, O 2 -sensitive K 1 channels: role of the Kv1.2 -subunit in mediating the hypoxic response, J. Physiol. (Lond.) 524 (2000) 783–793. [3] D.F. Donnelly, Developmental changes in membrane properties of chemoreceptor afferent neurons of the rat petrosal ganglia, J. Neurophysiol. 82 (1999) 209–215. [4] D.F. Donnelly, K 1 currents of glomus cells and chemosensory functions of carotid body, Respir. Physiol. 1151 (1999) 51–60. [5] F. Duprat, E. Guillemare, G. Romey, M. Fink, F. Lesage, M. Lazdunski, E. Honore, Susceptibility of cloned K 1 channels to
[6]
[7]
[8]
[9]
[10]
203
reactive oxygen species, Proc. Natl. Acad. Sci. USA 92 (1995) 11796–11800. D.M. Katz, I.B. Black, Expression and regulation of catecholaminergic traits in primary sensory neurons: relationship to target innervation in vivo, J. Neurosci. 6 (1986) 983–989. A.J. Patel, M. Lazdunski, E. Honore, Kv2.1 / Kv9.3, a novel ATPdependent delayed-rectifier K 1 channel in oxygen-sensitive pulmonary artery myocytes, EMBO J. 16 (1997) 6615–6625. M.T. Perez-Garcia, J.R. Lopez-Lopez, C. Gonzalez, Kvbeta1.2 subunit coexpression in HEK293 cells confers O 2 sensitivity to Kv4.2 but not to Shaker channels, J. Gen. Physiol. 113 (1999) 897–907. A. Stea, C.A. Nurse, Whole-cell currents in two subpopulations of cultured rat petrosal neurons with different tetrodotoxin sensitivities, Neuroscience 47 (1992) 727–736. J. Wang, M. Juhaszova, L.J. Rubin, X.J. Yuan, Hypoxia inhibits gene expression of voltage-gated K 1 channel alpha subunits in pulmonary artery smooth muscle cells, J. Clin. Invest. 100 (1997) 2347–2353.
Short communication
Voltage-gated K 1 channels in chemoreceptor sensory neurons of rat petrosal ganglion Ellen M. Andrews, Diana L. Kunze* Rammelkamp Center for Education and Research, MetroHealth Medical System and Department of Neurosciences, Case Western Reserve University, 2500 MetroHealth Drive, Cleveland, OH 44109 -1998, USA Accepted 9 January 2001
Abstract A subpopulation of sensory neurons in the petrosal ganglion transmits information between peripheral chemoreceptors (glomus cells) in the carotid body and relay neurons in the nucleus of the solitary tract. Expression of voltage-gated K 1 channels in these neurons was characterized by immunohistochemical localization. Five members of the Kv1 family, Kv1.1, Kv1.2, Kv1.4, Kv1.5 and Kv1.6 and members of two other families, Kv2.1 and Kv4.3, were identified in over 90% of the chemoreceptor neurons. Although the presence of these channel proteins was consistent throughout the population, individual neurons showed considerable variation in K 1 current profiles. 2001 Published by Elsevier Science B.V. Theme: Endocrine and autonomic regulation Topic: Respiratory regulation Keywords: Petrosal; Chemoreceptor; K 1 channel
The transmission of the signal from the chemoreceptors in the carotid body to the nucleus of the solitary tract is dependent on the voltage-gated K 1 (Kv) channels. While there is a substantial body of electrophysiological studies characterizing Kv channels in the chemoreceptor type 1 glomus cells [4], there is relatively little information on the sensory neurons they activate. A large number of distinct Kv channels have been cloned and characterized. Each has unique characteristics that may influence the neuronal activity in a different way. Our objective was to identify the Kv channels expressed in the population of petrosal neurons that are part of the peripheral chemoreceptor reflex pathway. These neurons were identified either by anterograde labeling from the carotid body or by the presence of immunoreactivity to the enzyme, tyrosine hydroxylase, TH [6]. Sprague–Dawley rats (2–3 weeks) were anesthetized with a cocktail of 0.1 ml ketamine HCl (100 mg / ml), 0.1 ml xylazine (20 mg / ml), and 0.2 ml acepromazine maleate *Corresponding author. Tel.: 11-216-778-8967; fax: 11-216-7782090. E-mail address: [email protected] (D.L. Kunze).
(10 mg / ml) at 1.2 ml / kg. The left carotid bifurcation was exposed and the carotid body isolated. Crystals of CM-DiI or DiI 291 (Molecular Probes) were placed on the carotid body and covered with Kwik-Sil (World Precision Instruments). After the Kwik-Sil hardened, the incision was sutured and the animal allowed to recover. A minimum of 3 days later the animal was sacrificed and the ganglion removed. The carotid body and the carotid sinus were examined to insure that the dye had remained confined to the carotid body region. For the immunohistochemistry studies, 16 labeled animals were anesthetized with halothane and decapitated. The petrosal ganglia were removed, frozen and serial 16 mm cryostat sections were fixed 15–20 min in 4% paraformaldehyde, 0.1 M lysine, 0.1 M sodium periodate, pH 6.2 and 0.1% Triton-X. Sections were rinsed and incubated with blocking solution (phosphate-buffered saline (PBS), 3% normal goat serum, 3% normal donkey serum, and 1% bovine serum albumin) for 30 min. All antibodies were diluted in blocking solution. Sections were incubated in primary antibodies 3 h at room temperature. The slides were rinsed in PBS and secondary antibodies were added for 90 min. Controls sections were incubated with PBS and appropriate sec-
0006-8993 / 01 / $ – see front matter 2001 Published by Elsevier Science B.V. PII: S0006-8993( 01 )02121-7
E.M. Andrews, D.L. Kunze / Brain Research 897 (2001) 199 – 203
200
Table 1 This table provides the number and percentage of neurons for which specific Kv channel antibodies co-localize with the TH antibody or with the CM-DiI labeled neurons Kv channel
Number of cells with both Kv and CM-DiI
Total number of CM-DiI cells
Percentage of co-localization
Number of cells with both Kv and TH
Total number of TH cells
Percentage of co-localization
mKv1.1 rKv1.2 mKv1.4 mKv1.5 rKv2.1 rKv4.3
142 195 172 154 95 82
146 198 172 158 102 85
97.3 98.5 100.0 97.5 93.0 96.5
69 114 221 109 111 147
69 129 229 133 115 159
100.0 89.0 96.5 94.2 96.5 92.4
ondary antibodies. Sections were rinsed, mounted in Vectashield (Vector Laboratories) with DAPI and viewed using an Olympus BH-2 fluorescent microscope. Individual cells were counted through successive sections by following the labeled nuclei. Each K 1 channel was studied in ganglia from two animals except where Kv1.1 was co-localized with TH, n51. The following commercial antibodies were used: anti-TH (Affinity BioReagents and DiaSorin), anti-Kv1.1 and anti-Kv1.4 (Upstate Biotechnology), anti-Kv1.5 (Transduction Laboratories), anti-Kv1.2, anti-Kv1.6 and anti-Kv4.3 (Alamone Labs) and antiKv2.1(Upstate Biotechnology). Secondary antibodies were obtained from Jackson ImmunoResearch Laboratories. For electrophysiological studies, petrosal ganglia were excised from rats in which the carotid body had been labeled. The ganglia were collected after halothane anesthesia followed by decapitation and incubated in Earle’s balanced saline solution (EBSS, Gibco BRL) containing 1 mg / ml collagenase 1 h at 378C. The enzyme-containing medium was replaced with 3 ml of Dulbecco’s modified Eagle’s medium / F-12 with 5% fetal bovine serum, 0.1% serum extender (Collaborative Research), 1% penicillin / streptomycin and 1.5 mg / ml albumin. The cells were dispersed and plated onto glass coverslips. K 1 currents were recorded using the patch technique for whole-cell recording, 4–24 h after plating. Data were digitized and analyzed using pClamp programs (Axon Instruments). The extracellular solution contained (in mM): 137 NMDG (N-methylD-glucamine), 5.4 KCl, 1 MgCl 2 , 0.02 CaCl 2 , 10 Glucose, 10 HEPES, pH 7.3 with KOH; the pipette solution contained (in mM) 145 K-aspartate, 1.95 CaCl 2 , 2.2 EGTA [ethylene-glycol-bis(b-amino ethylether)-N,N9tetra-acetic acid], 2 MgCl 2 , 10 Glucose, and 5 HEPES, pH 7.3 with KOH. Expression of Kv1.1, Kv1.2, Kv1.4, Kv1.5, Kv1.6, Kv2.1 and Kv4.3 was observed in petrosal neurons whose afferent terminals project from the carotid body by co-
localization with CM DiI (Table 1 and Fig. 1) or by the presence of TH. With the exception of a slightly smaller percentage of Kv1.2 in TH-containing cells (89%), the presence of these Kv channels was .92% in both THcontaining neurons and those labeled with CM-DiI. Since a small population of TH-immunoreactive petrosal neurons do not project to the carotid body [6], some TH-containing cells may signal other modalities. The level of expression as indicated by the intensity of the fluorescence was variable within the population. The staining was, for the most part, cytoplasmic with some perinuclear localization. The label appears to extend to the plasma membrane but at the light microscopic level it is difficult to localize the protein to the membrane itself. The variability in the level of staining among neurons suggested non-uniformity in the somal K 1 currents. K 1 currents were recorded from primary cultures of DiI 291labeled petrosal neurons. Representative examples of current profiles from 3 / 18 neurons from three animals were selected to show the variability within this population of sensory neurons. The most obvious difference among neurons was the amplitude of an early transient phase. This was pronounced in a rare large neuron (90 pF) that showed an initial large transient component that decays to a steady current (Fig. 2A). The voltage-dependence of inactivation of the transient phase following 1 s prepulses shows the transient phase inactivated between 2110 and 260 mV. This is in contrast to a second neuron (44 pF) in which the transient phase is small compared to the slowly developing steady-state current (Fig. 2B). In this neuron the voltagedependence of inactivation occurred at more depolarized potentials. In the third neuron, a small cell (33 pF), the transient phase was not evident in the whole-cell currents in response to voltage steps or during the inactivation protocol (Fig. 2C). The steady-state currents also show differences in the voltage-dependence of activation. In summary, immunoreactivity for Kv1.1, Kv1.2, Kv1.4,
Fig. 1. (A–D) Photomicrographs of chemoreceptor neurons in the petrosal ganglion double-stained for tyrosine hydroxylase (TH) using a rhodamineconjugated (red; A, D) or FITC-labeled (green; B, C) secondary antibodies and antibodies for voltage-gated K 1 channels (Kv) using rhodamine-conjugated (red; B, C) or FITC-labeled (green; A, D) secondary antibodies: (A) Kv1.1; (B) Kv1.6; (C) Kv4.3; and (D) Kv1.5. (E–H) Photomicrographs of sensory neurons in the petrosal ganglion labeled with CM DiI which is seen as yellow / orange particles within the neurons. The sections were stained for presence of antibodies against Kv channels: (E) Kv1.2; (F) Kv1.4; (G) Kv2.1; and (H) Kv1.5, using FITC-labeled secondary antibodies (green). Arrows indicate examples of co-localization (yellow / orange). Nuclei are stained with DAPI (blue). Scale bar550 mm.
E.M. Andrews, D.L. Kunze / Brain Research 897 (2001) 199 – 203
201
202
E.M. Andrews, D.L. Kunze / Brain Research 897 (2001) 199 – 203
Fig. 2. Examples of diversity in K 1 currents recorded from three chemoreceptor neurons. (A–C) Left panel illustrates the current response to 300 ms depolarizing steps from 270 mV to 140 mV in 10 mV increments from a holding potential of 290 mV. The middle panel illustrates the current –voltage relationships of the peak of the transient current at the beginning of the pulse (A and B) and the steady-state currents taken at the end of the pulse (A, B and C). The right panel gives the voltage dependence of inactivation for the peak of the transient current at the beginning of the pulse (A, B) or for (C), the steady current. Examples of the current used to obtain this curve are given in the inset. The currents were obtained during a step to 20 mV from 1 s prepulses of 2110 to 210 mV. The range of prepulses selected for the inset is indicated for each cell. Capacitance of neurons in A–C, 90 pF, 44 pF and 33 pF, respectively.
Kv1.5, Kv1.6, Kv2.1 and Kv4.3 was present but not of uniform intensity in the chemoreceptor cells of the petrosal ganglion. It is not surprising that the K 1 channel expression levels may differ since these neurons are not a homogenous population with regard to neurotransmitter content or sodium channel composition. Clearly there is also a difference in potassium channel profiles. A previous study that reported there were no obvious transient K 1 currents in rat petrosal neurons [9]. This would be consistent with our results if the K 1 currents we recorded in the small cells were representative of the unmyelinated population that Donnelly [3] recently reported represents most of the chemoreceptor cells in the rat. Strategies for isolating the specific currents, such as selective toxins,
introduction of antisense constructs or blocking antibodies, will be needed to associate individual Kv a subunits with specific components of the current. Interestingly, several of the K 1 channels reported here have been shown to modified by hypoxia [1,2,5,7,8,10]. Modulation of K 1 channel activity by hypoxia in the chemoreceptor reflex pathways beyond the glomus cell should be explored.
Acknowledgements The authors wish to thank Pat Glazebrook for her technical advice. This work was supported by PHHS grant HL25830.
E.M. Andrews, D.L. Kunze / Brain Research 897 (2001) 199 – 203
References [1] S.L. Archer, E. Souil, A.T. Dinh-Xuan, B. Schremmer, J.C. Mercier, A. El Yaagoubi, L. Nguyen-Huu, H.L. Reeve, V. Hampl, Molecular identification of the role of voltage-gated K 1 channels, Kv1.5 and Kv2.1, in hypoxic pulmonary vasoconstriction and control of resting membrane potential in rat pulmonary artery myocytes, J. Clin. Invest. 101 (1998) 2319–2330. [2] L. Conforti, I. Bodi, J.W. Nisbet, D.E. Millhorn, O 2 -sensitive K 1 channels: role of the Kv1.2 -subunit in mediating the hypoxic response, J. Physiol. (Lond.) 524 (2000) 783–793. [3] D.F. Donnelly, Developmental changes in membrane properties of chemoreceptor afferent neurons of the rat petrosal ganglia, J. Neurophysiol. 82 (1999) 209–215. [4] D.F. Donnelly, K 1 currents of glomus cells and chemosensory functions of carotid body, Respir. Physiol. 1151 (1999) 51–60. [5] F. Duprat, E. Guillemare, G. Romey, M. Fink, F. Lesage, M. Lazdunski, E. Honore, Susceptibility of cloned K 1 channels to
[6]
[7]
[8]
[9]
[10]
203
reactive oxygen species, Proc. Natl. Acad. Sci. USA 92 (1995) 11796–11800. D.M. Katz, I.B. Black, Expression and regulation of catecholaminergic traits in primary sensory neurons: relationship to target innervation in vivo, J. Neurosci. 6 (1986) 983–989. A.J. Patel, M. Lazdunski, E. Honore, Kv2.1 / Kv9.3, a novel ATPdependent delayed-rectifier K 1 channel in oxygen-sensitive pulmonary artery myocytes, EMBO J. 16 (1997) 6615–6625. M.T. Perez-Garcia, J.R. Lopez-Lopez, C. Gonzalez, Kvbeta1.2 subunit coexpression in HEK293 cells confers O 2 sensitivity to Kv4.2 but not to Shaker channels, J. Gen. Physiol. 113 (1999) 897–907. A. Stea, C.A. Nurse, Whole-cell currents in two subpopulations of cultured rat petrosal neurons with different tetrodotoxin sensitivities, Neuroscience 47 (1992) 727–736. J. Wang, M. Juhaszova, L.J. Rubin, X.J. Yuan, Hypoxia inhibits gene expression of voltage-gated K 1 channel alpha subunits in pulmonary artery smooth muscle cells, J. Clin. Invest. 100 (1997) 2347–2353.