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Possible involvement of presynaptic alpha 1-adrenoceptors in the effects of idazoxan and prazosin on 3H-noradrenaline release from tail arteries of SHR.
Naunyn Schmiedebergs Arch Pharmacol. 1986 Aug; 333(4):354-61.NS

Abstract

The effects of several alpha-adrenoceptor antagonists have been examined on tritium release elicited by electrical stimulation from isolated perfused SHR tail artery preparations prelabelled with 3H-noradrenaline (3H-NA). Phentolamine and yohimbine potently facilitated the stimulation evoked release of tritium at low frequencies of stimulation, but the alpha 2-adrenoceptor antagonist idazoxan was only weakly active at 1 mumol/l, despite antagonising the clonidine-evoked inhibition of 3H-release at a lower concentration of 0.1 mumol/l. The alpha 1-adrenoceptor antagonists prazosin and corynanthine also increased stimulation evoked tritium release in this preparation, suggesting the presence of prejunctional alpha 1-adrenoceptors. Furthermore, the alpha 1-adrenoceptor agonist methoxamine (3 mumol/l) caused a significant inhibition of tritium-evoked release, an effect which was blocked by prazosin (10 nmol/l). When alpha 1-adrenoceptors were blocked in the presence of prazosin, idazoxan (0.1 mumol/l) produced a significant facilitatory effect on the electrically-evoked release of 3H-transmitter. On the other hand, when alpha 2-adrenoceptors were blocked in the presence of yohimbine, exposure to idazoxan (0.1 mumol/l) reduced significantly the stimulation-evoked release of tritium elicited by electrical stimulation. The results indicate that in the SHR tail arteries, idazoxan has a partial agonist inhibitory activity on transmitter release, which can mask the facilitatory effects due to blockade of presynaptic alpha 2-adrenoceptors. The inhibitory effects of idazoxan appear to involve presynaptic alpha 1-adrenoceptors, which when stimulated, reduce 3H-NA release in SHR tail arteries.

Authors

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Pub Type(s)

Journal Article

Language

eng

PubMed ID

2877400

Citation

Hicks, P E., et al. "Possible Involvement of Presynaptic Alpha 1-adrenoceptors in the Effects of Idazoxan and Prazosin On 3H-noradrenaline Release From Tail Arteries of SHR." Naunyn-Schmiedeberg's Archives of Pharmacology, vol. 333, no. 4, 1986, pp. 354-61.
Hicks PE, Najar M, Vidal M, et al. Possible involvement of presynaptic alpha 1-adrenoceptors in the effects of idazoxan and prazosin on 3H-noradrenaline release from tail arteries of SHR. Naunyn Schmiedebergs Arch Pharmacol. 1986;333(4):354-61.
Hicks, P. E., Najar, M., Vidal, M., & Langer, S. Z. (1986). Possible involvement of presynaptic alpha 1-adrenoceptors in the effects of idazoxan and prazosin on 3H-noradrenaline release from tail arteries of SHR. Naunyn-Schmiedeberg's Archives of Pharmacology, 333(4), 354-61.
Hicks PE, et al. Possible Involvement of Presynaptic Alpha 1-adrenoceptors in the Effects of Idazoxan and Prazosin On 3H-noradrenaline Release From Tail Arteries of SHR. Naunyn Schmiedebergs Arch Pharmacol. 1986;333(4):354-61. PubMed PMID: 2877400.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Possible involvement of presynaptic alpha 1-adrenoceptors in the effects of idazoxan and prazosin on 3H-noradrenaline release from tail arteries of SHR. AU - Hicks,P E, AU - Najar,M, AU - Vidal,M, AU - Langer,S Z, PY - 1986/8/1/pubmed PY - 1986/8/1/medline PY - 1986/8/1/entrez SP - 354 EP - 61 JF - Naunyn-Schmiedeberg's archives of pharmacology JO - Naunyn Schmiedebergs Arch Pharmacol VL - 333 IS - 4 N2 - The effects of several alpha-adrenoceptor antagonists have been examined on tritium release elicited by electrical stimulation from isolated perfused SHR tail artery preparations prelabelled with 3H-noradrenaline (3H-NA). Phentolamine and yohimbine potently facilitated the stimulation evoked release of tritium at low frequencies of stimulation, but the alpha 2-adrenoceptor antagonist idazoxan was only weakly active at 1 mumol/l, despite antagonising the clonidine-evoked inhibition of 3H-release at a lower concentration of 0.1 mumol/l. The alpha 1-adrenoceptor antagonists prazosin and corynanthine also increased stimulation evoked tritium release in this preparation, suggesting the presence of prejunctional alpha 1-adrenoceptors. Furthermore, the alpha 1-adrenoceptor agonist methoxamine (3 mumol/l) caused a significant inhibition of tritium-evoked release, an effect which was blocked by prazosin (10 nmol/l). When alpha 1-adrenoceptors were blocked in the presence of prazosin, idazoxan (0.1 mumol/l) produced a significant facilitatory effect on the electrically-evoked release of 3H-transmitter. On the other hand, when alpha 2-adrenoceptors were blocked in the presence of yohimbine, exposure to idazoxan (0.1 mumol/l) reduced significantly the stimulation-evoked release of tritium elicited by electrical stimulation. The results indicate that in the SHR tail arteries, idazoxan has a partial agonist inhibitory activity on transmitter release, which can mask the facilitatory effects due to blockade of presynaptic alpha 2-adrenoceptors. The inhibitory effects of idazoxan appear to involve presynaptic alpha 1-adrenoceptors, which when stimulated, reduce 3H-NA release in SHR tail arteries. SN - 0028-1298 UR - https://www.unboundmedicine.com/medline/citation/2877400/Possible_involvement_of_presynaptic_alpha_1_adrenoceptors_in_the_effects_of_idazoxan_and_prazosin_on_3H_noradrenaline_release_from_tail_arteries_of_SHR_ DB - PRIME DP - Unbound Medicine ER -