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Selected Publication:
Boehm, S; Huck, S.
Modulation of calcium currents via alpha 2-adrenoceptors in embryonic chick sympathetic neurons.
Naunyn Schmiedebergs Arch Pharmacol. 1991; 344(3):382-385
Doi: 10.1007/BF00183015
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- Leading authors Med Uni Graz
- Böhm Stefan
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- Abstract:
- In order to gain insight into the mechanism of the autoinhibition of noradrenaline release, the present study explores the effects of substances acting at various adrenoceptor-subtypes on voltage-activated Ca2+ currents. Experiments were carried out on cultured embryonic chick sympathetic neurons using the patch clamp technique. Ca2+ currents associated with a (fully activating) depolarizing 150 ms voltage step to 0 mV were reduced by noradrenaline and the two alpha 2-adrenoceptor agonists UK 14,304 and clonidine, predominantly during the early phase of activation. We quantified these effects by measuring Ca2+ current amplitudes in the absence and presence of substances 10 ms after the beginning of the depolarization. Noradrenaline effects were maximal at 5 mumol/l, causing a 28% depression of the current. Half-maximal effects (IC50) were apparent at 0.7 mumol/l. UK 14,304 was equipotent to noradrenaline (IC50: 0.5 mumol/l; maximal effect: 26% depression). Clonidine, while active in the same range of concentration (IC50: 0.6 mumol/l), had a smaller maximal effect (20% depression). Methoxamine and isoprenaline, on the other hand, did not significantly reduce the Ca2+ current at 10 mumol/l. The noradrenaline-induced inhibition was attenuated by yohimbine (1 mumol/l). Neither prazosin (1 mumol/l) nor propranolol (1 mumol/l) interfered with the effect of noradrenaline. These results indicate a reduction of Ca2+ influx via alpha 2-adrenoceptors and suggest that the autoreceptor-mediated inhibition of transmitter release in embryonic chick sympathetic neurons operates through the modulation of Ca2+ channels.
- Find related publications in this database (using NLM MeSH Indexing)
- Adrenergic alpha-Agonists - pharmacology
- Adrenergic alpha-Antagonists - pharmacology
- Animals -
- Calcium - physiology
- Chick Embryo -
- Clonidine - pharmacology
- Electric Stimulation -
- Electrophysiology -
- Ganglia, Sympathetic - drug effects
- Neurons - drug effects
- Norepinephrine - pharmacology
- Quinoxalines - pharmacology
- Receptors, Adrenergic, alpha - physiology
- Sympathetic Nervous System - cytology
- Find related publications in this database (Keywords)
- CHICK SYMPATHETIC NEURONS
- CA2+ CURRENTS
- ALPHA-2-ADRENOCEPTORS
- PATCH CLAMP