title: Membrane properties and the excitatory junction potentials in smooth muscle cells of cochlear spiral modiolar artery in guinea pigs.
abstract: Blood circulation changes in the inner ear play an important role in many physiological and pathological conditions of hearing function. The spiral modiolar artery (SMA) is the terminal artery to the cochlea. It was surrounded with nerve fibers immunostained by an antibody for tyrosine hydroxylase. By using intracellular recording techniques on the acutely isolated SMA, membrane properties of the smooth muscle cells and the neuromuscular transmission in this preparation were investigated. With minimum tension and normal extracellular K(+) concentration (5 mM), the majority of muscle cells showed a resting potential near -80 mV and an input resistance of about 8 MOmega. V/I plot showed an inward rectification in these cells. Barium (50-500 microM) caused strong depolarization and an increase in input resistance. Transmural electrical stimulation evoked stimulation intensity-dependent depolarizations (2-31 mV) following a short latency ( approximately 20 ms). The evoked potential by a low intensity stimulus was completely blocked by 1 microM tetrodotoxin. The potential and a depolarization induced by norepinephrine (10 microM) was usually partially (40-90%) blocked by alpha-receptor antagonists prazosin and/or idazoxan with concentrations up to 1 microM. Action potentials were observed when the depolarization was more than -40 mV. It is concluded that SMA smooth muscle cells, similar to those in other brain small arteries, highly express inward rectifying potassium channels; the cells receive catecholaminergic innervation, and stimulation of the nerves elicited an excitatory junction potential that is partially mediated by adrenergic receptors.
authors.affiliation: Oregon Hearing Research Center, NRC-04, Oregon Health Sciences University, Portland, OR 97201, USA. jiangz@ohsu.edu
authors.forename: Z G
authors.initials: ZG
authors.lastname: Jiang
authors.forename: J
authors.initials: J
authors.lastname: Qiu
authors.forename: T
authors.initials: T
authors.lastname: Ren
authors.forename: A L
authors.initials: AL
authors.lastname: Nuttall
mesh_terms: D000818:Animals; D001158:Arteries / Q000166:cytology / Q000502:physiology; D003051:Cochlea / Q000098:blood supply*; D004594:Electrophysiology; D017629:Gap Junctions / Q000502:physiology*; D006168:Guinea Pigs; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D009638:Norepinephrine / Q000494:pharmacology; D011942:Receptors, Adrenergic, alpha / Q000502:physiology
chemical_list: D011942:Receptors, Adrenergic, alpha; D009638:Norepinephrine