The Ca2+-activated Cl− channel TMEM16B regulates action potential firing and axonal targeting in olfactory sensory neurons

The Ca2+-activated Cl− channel TMEM16B is highly expressed in the cilia of olfactory sensory neurons (OSNs). Although a large portion of the odor-evoked transduction current is carried by Ca2+-activated Cl− channels, their role in olfaction is still controversial. A previous report (Billig et al. 2011. Nat. Neurosci. http://dx.doi.org/10.1038/nn.2821) showed that disruption of the TMEM16b/Ano2 gene in mice abolished Ca2+-activated Cl− currents in OSNs but did not produce any major change in olfactory behavior. Here we readdress the role of TMEM16B in olfaction and show that TMEM16B knockout (KO) mice have behavioral deficits in odor-guided food-finding ability. Moreover, as the role of TMEM16B in action potential (AP) firing has not yet been studied, we use electrophysiological recording methods to measure the firing activity of OSNs. Suction electrode recordings from isolated olfactory neurons and on-cell loose-patch recordings from dendritic knobs of neurons in the olfactory epithelium show that randomly selected neurons from TMEM16B KO mice respond to stimulation with increased firing activity than those from wild-type (WT) mice. Because OSNs express different odorant receptors (ORs), we restrict variability by using a mouse line that expresses a GFP-tagged I7 OR, which is known to be activated by heptanal. In response to heptanal, we measure dramatic changes in the firing pattern of I7-expressing neurons from TMEM16B KO mice compared with WT: responses are prolonged and display a higher number of APs. Moreover, lack of TMEM16B causes a markedly reduced basal spiking activity in I7-expressing neurons, together with an alteration of axonal targeting to the olfactory bulb, leading to the appearance of supernumerary I7 glomeruli. Thus, TMEM16B controls AP firing and ensures correct glomerular targeting of OSNs expressing I7. Altogether, these results show that TMEM16B does have a relevant role in normal olfaction.

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pigkMutation underliesmachobehavior and affects Rohon-Beard cell excitability

Journal of Neurophysiology ◽

10.1152/jn.00355.2015 ◽

2015 ◽

Vol 114 (2) ◽

pp. 1146-1157 ◽

Cited By ~ 2

Author(s):

V. Carmean ◽

M. A. Yonkers ◽

M. B. Tellez ◽

J. R. Willer ◽

G. B. Willer ◽

...

Keyword(s):

Action Potential ◽

Sensory Neurons ◽

Sodium Current ◽

Genetic Defect ◽

Sensory Cells ◽

Loss Of Function ◽

Wild Type ◽

Action Potential Firing ◽

Potential Firing ◽

Touch Response

The study of touch-evoked behavior allows investigation of both the cells and circuits that generate a response to tactile stimulation. We investigate a touch-insensitive zebrafish mutant, macho (maco), previously shown to have reduced sodium current amplitude and lack of action potential firing in sensory neurons. In the genomes of mutant but not wild-type embryos, we identify a mutation in the pigk gene. The encoded protein, PigK, functions in attachment of glycophosphatidylinositol anchors to precursor proteins. In wild-type embryos, pigk mRNA is present at times when mutant embryos display behavioral phenotypes. Consistent with the predicted loss of function induced by the mutation, knock-down of PigK phenocopies maco touch insensitivity and leads to reduced sodium current (INa) amplitudes in sensory neurons. We further test whether the genetic defect in pigk underlies the maco phenotype by overexpressing wild-type pigk in mutant embryos. We find that ubiquitous expression of wild-type pigk rescues the touch response in maco mutants. In addition, for maco mutants, expression of wild-type pigk restricted to sensory neurons rescues sodium current amplitudes and action potential firing in sensory neurons. However, expression of wild-type pigk limited to sensory cells of mutant embryos does not allow rescue of the behavioral touch response. Our results demonstrate an essential role for pigk in generation of the touch response beyond that required for maintenance of proper INa density and action potential firing in sensory neurons.

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cAMP-independent effects of 8-(4-parachlorophenylthio)-cyclic AMP on spike duration and membrane currents in pleural sensory neurons of Aplysia

Journal of Neurophysiology ◽

10.1152/jn.1994.72.3.1250 ◽

1994 ◽

Vol 72 (3) ◽

pp. 1250-1259 ◽

Cited By ~ 9

Author(s):

S. Sugita ◽

D. A. Baxter ◽

J. H. Byrne

Keyword(s):

Protein Kinase ◽

Action Potential ◽

Voltage Clamp ◽

Sensory Neurons ◽

Membrane Current ◽

Membrane Currents ◽

Cyclic Monophosphate ◽

Subsequent Application ◽

Independent Effects

1. The serotonergic modulation of pleural sensory neurons in Aplysia is mediated via two second messenger systems: the adenosine cyclic monophosphate/protein kinase A (cAMP/PKA) and diacylglycerol/protein kinase C systems. Often membrane permeable derivatives of cAMP, such as 8-(4-parachlorophenylthio)-cAMP (pcpt-cAMP), have been used to investigate the role of cAMP/PKA in modulating sensory neurons. In light of recent findings that pcpt-cAMP may have cAMP-independent actions, we have reexamined the effects of pcpt-cAMP on the action potential and membrane currents of the sensory neurons. 2. Although pcpt-cAMP (500 microM to 1 mM) and serotonin (5-HT; 10 microM) induced comparable measures of spike broadening (an average increase above baseline of 29 and 40%, respectively), the broadening produced by the two was qualitatively different. Serotonin-induced broadening developed slowly over 9-12 min, was most prominent during later phases of the spike repolarization, and reduced the spike afterhyperpolarization. In contrast, pcpt-cAMP-induced broadening developed rapidly, was rather uniform throughout the repolarization phase of the spike, delayed the peak of the action potential, and increased the afterhyperpolarization. 3. Preexposure of sensory neurons to 5-HT did not occlude further spike broaden by subsequent application of pcpt-cAMP. Indeed the effects of the two were additive. In addition, the effects of pcpt-cAMP were not mimicked by another analogue of cAMP, 8-bromo-cAMP. Interestingly, most of the effects of pcpt-cAMP on the action potential were mimicked by 8-(4-parachlorophenyl-thio)-guanosine cyclic monophosphate (pcpt-cGMP), but not by 8-bromo-cGMP. 4. During voltage-clamp pulses to 20 mV, pcpt-cAMP reduced the membrane current throughout the voltage-clamp pulse, which was qualitatively different from the modulation of the membrane current by 5-HT. In addition, the pcpt-cAMP-induced reduction in the membrane current at the beginning of the pulse was much greater than that induced by 5-HT. Moreover, preexposure of sensory neurons to 5-HT did not occlude further reduction in the membrane current by subsequent application of pcpt-cAMP. 5. These results suggest that pcpt-cAMP has some mechanisms of action that are not shared by 5-HT or cAMP but are shared by pcpt-cGMP. In addition, these findings provide further evidence that results obtained with this compound should be interpreted with caution.

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Stabilizing Role of Calcium Store-Dependent Plasma Membrane Calcium Channels in Action-Potential Firing and Intracellular Calcium Oscillations

Biophysical Journal ◽

10.1529/biophysj.105.062984 ◽

2005 ◽

Vol 89 (6) ◽

pp. 3741-3756 ◽

Cited By ~ 17

Author(s):

J.M.A.M. Kusters ◽

M.M. Dernison ◽

W.P.M. van Meerwijk ◽

D.L. Ypey ◽

A.P.R. Theuvenet ◽

...

Keyword(s):

Plasma Membrane ◽

Calcium Channels ◽

Action Potential ◽

Intracellular Calcium ◽

Calcium Oscillations ◽

Action Potential Firing ◽

Calcium Store ◽

Potential Firing

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Neurological Basis of AMP-Dependent Thermoregulation and its Relevance to Central and Peripheral Hyperthermia

Journal of Cerebral Blood Flow & Metabolism ◽

10.1038/jcbfm.2012.157 ◽

2012 ◽

Vol 33 (2) ◽

pp. 183-190 ◽

Cited By ~ 33

Author(s):

Mirko Muzzi ◽

Francesco Blasi ◽

Alessio Masi ◽

Elisabetta Coppi ◽

Chiara Traini ◽

...

Keyword(s):

Body Temperature ◽

Preoptic Area ◽

Febrile Illness ◽

Electrophysiological Recording ◽

Spontaneous Firing ◽

Nucleotidase Activity ◽

Firing Activity ◽

Hypothermic Effect ◽

Adenosine A1

Therapeutic hypothermia is of relevance to treatment of increased body temperature and brain injury, but drugs inducing selective, rapid, and safe cooling in humans are not available. Here, we show that injections of adenosine 5′-monophosphate (AMP), an endogenous nucleotide, promptly triggers hypothermia in mice by directly activating adenosine A1 receptors (A1R) within the preoptic area (POA) of the hypothalamus. Inhibition of constitutive degradation of brain extracellular AMP by targeting ecto 5′-nucleotidase, also suffices to prompt hypothermia in rodents. Accordingly, sensitivity of mice and rats to the hypothermic effect of AMP is inversely related to their hypothalamic 5′-nucleotidase activity. Single-cell electrophysiological recording indicates that AMP reduces spontaneous firing activity of temperature-insensitive neurons of the mouse POA, thereby retuning the hypothalamic thermoregulatory set point towards lower temperatures. Adenosine 5′-monophosphate also suppresses prostaglandin E2-induced fever in mice, having no effects on peripheral hyperthermia triggered by dioxymetamphetamine (ecstasy) overdose. Together, data disclose the role of AMP, 5′-nucleotidase, and A1R in hypothalamic thermoregulation, as well and their therapeutic relevance to treatment of febrile illness.

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Postnatal maturation of the hyperpolarization-activated cation current, Ih, in trigeminal sensory neurons

Journal of Neurophysiology ◽

10.1152/jn.00798.2010 ◽

2011 ◽

Vol 106 (4) ◽

pp. 2045-2056 ◽

Cited By ~ 12

Author(s):

Hyun-jung Cho ◽

John B. Furness ◽

Ernest A. Jennings

Keyword(s):

Action Potential ◽

Postnatal Development ◽

Sensory Neurons ◽

Neuronal Excitability ◽

Firing Frequency ◽

Moderate Intensity ◽

Hcn Channels ◽

Action Potential Firing ◽

Membrane Hyperpolarization ◽

Postnatal Maturation

Hyperpolarization-activated inward currents ( Ih) contribute to neuronal excitability in sensory neurons. Four subtypes of hyperpolarization-activated cyclic nucleotide-gated (HCN) channels generate Ih, with different activation kinetics and cAMP sensitivities. The aim of the present study was to examine the postnatal development of Ih and HCN channel subunits in trigeminal ganglion (TG) neurons. Ih was investigated in acutely dissociated TG neurons from rats aged between postnatal day (P)1 and P35 with whole cell patch-clamp electrophysiology. In voltage-clamp studies, Ih was activated by a series of hyperpolarizing voltage steps from −40 mV to −120 mV in −10-mV increments. Tail currents from a common voltage step (−100 mV) were used to determine Ih voltage dependence. Ih activation was faster in older rats and occurred at more depolarized potentials; the half-maximal activation voltage ( V1/2) changed from −89.4 mV (P1) to −81.6 mV (P35). In current-clamp studies, blocking Ih with ZD7288 caused membrane hyperpolarization and increases in action potential half-duration at all postnatal ages examined. ZD7288 also reduced the action potential firing frequency in multiple-firing neurons. Western blot analysis of the TG detected immunoreactive bands corresponding to all HCN subtypes. HCN1 and HCN2 band density increased with postnatal age, whereas the low-intensity HCN3 and moderate-intensity HCN4 bands were not changed. This study suggests that functional Ih are activated in rat trigeminal sensory neurons from P1 during postnatal development, have an increasing role with age, and modify neuronal excitability.

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