Inhibition of K+ permeability diminishes alpha 2-adrenoceptor mediated effects on norepinephrine release
The effect of two different potassium channel blockers, 4-aminopyridine (4-AP) and quinine, on the alpha 2-adrenoceptor mediated modulation of norepinephrine (NE) release was investigated. Pairs of mouse vasa deferentia were loaded with /sup 3/H-norepinephrine (/sup 3/H-NE), superfused continuously, and stimulated electrically. 4-AP (5.3 x 10(-4) M), and quinine (10(-5) M) enhanced the stimulation-evoked release of tritium significantly. The electrically induced release of radioactivity was reduced by alpha 2-adrenoceptor agonists (1-NE and xylazine) and enhanced by the alpha 2-adrenoceptor antagonist yohimbine. Both effects were affected markedly by 4-AP or quinine: the depressant action of 1-NA and xylazine was partially antagonized and the facilitatory effect of yohimbine was completely abolished during the blockade of the potassium channels. It is suggested that the blockade of the potassium permeability counteracts negative feedback modulation; therefore, it seems likely that the stimulation of alpha 2-adrenoceptors leads to an enhanced potassium permeability and hyperpolarization of varicose axon terminals.
- Research Organization:
- Institute of Experimental Medicine, Budapest (Hungary)
- OSTI ID:
- 6681945
- Journal Information:
- J. Neurosci. Res.; (United States), Journal Name: J. Neurosci. Res.; (United States) Vol. 20:1; ISSN JNRED
- Country of Publication:
- United States
- Language:
- English
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59 BASIC BIOLOGICAL SCIENCES
ADRENAL HORMONES
ALKALI METALS
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