title: The h-current in periglomerular dopaminergic neurons of the mouse olfactory bulb.
abstract: The properties of the hyperpolarization-activated cation current (I(h)) were investigated in rat periglomerular dopaminergic neurons using patch-clamp recordings in thin slices. A reliable identification of single dopaminergic neurons was made possible by use of a transgenic line of mice expressing eGFP under the tyrosine hydroxylase promoter. At 37 °C and minimizing the disturbance of the intracellular milieu with perforated patches, this current shows a midpoint of activation around -82.7 mV, with a significant level of opening already at rest, thereby giving a substantial contribution to the resting potential, and ultimately playing a relevant function in the control of the cell excitability. The blockage of I(h) has a profound influence on the spontaneous firing of these neurons, which result as strongly depressed. However the effect is not due to a direct role of the current in the pacemaker process, but to the I(h) influence on the resting membrane potential. I(h) kinetics is sensitive to the intracellular levels of cAMP, whose increase promotes a shift of the activation curve towards more positive potentials. The direct application of DA and 5-HT neurotransmitters, physiologically released onto bulbar dopaminergic neurons and known to act on metabotropic receptors coupled to the cAMP pathway, do not modifythe I(h) amplitude. On the contrary, noradrenaline almost halves the I(h) amplitude. Our data indicate that the HCN channels do not participate directly to the pacemaker activity of periglomerular dopaminergic neurons, but influence their resting membrane potential by controlling the excitability profile of these cells, and possibly affecting the processing of sensory information taking place at the entry of the bulbar circuitry.
authors: Dipartimento di Scienze della Vita e Biotecnologie, University of Ferrara and Istituto Nazionale di Neuroscienze, Ferrara, Italy.
authors: Angela
authors: A
authors: Pignatelli
authors: Mirta
authors: M
authors: Borin
authors: Alex
authors: A
authors: Fogli Iseppe
authors: Cristina
authors: C
authors: Gambardella
authors: Ottorino
authors: O
authors: Belluzzi
mesh_terms: D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000316:Adrenergic alpha-Agonists / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D001552:Benzazepines / Q000494:pharmacology; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism / Q000494:pharmacology; D054815:Cyclic Nucleotide-Gated Cation Channels / Q000378:metabolism / Q000502:physiology*; D004298:Dopamine / Q000378:metabolism / Q000494:pharmacology; D059290:Dopaminergic Neurons / Q000378:metabolism / Q000502:physiology*; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels; D000077550:Ivabradine; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009638:Norepinephrine / Q000378:metabolism / Q000494:pharmacology; D009830:Olfactory Bulb / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000378:metabolism / Q000502:physiology*; D011743:Pyrimidines / Q000494:pharmacology; D051381:Rats; D014446:Tyrosine 3-Monooxygenase / Q000235:genetics / Q000378:metabolism
chemical_list: D000316:Adrenergic alpha-Agonists; D001552:Benzazepines; D054815:Cyclic Nucleotide-Gated Cation Channels; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels; D015221:Potassium Channels; D011743:Pyrimidines; C082246:ICI D2788; D049452:Green Fluorescent Proteins; D005576:Colforsin; D000077550:Ivabradine; D000242:Cyclic AMP; D014446:Tyrosine 3-Monooxygenase; D015056:1-Methyl-3-isobutylxanthine; D004298:Dopamine; D009638:Norepinephrine