Reduced inhibitory effects of clonidine and neuropeptide Y on 3H-noradrenaline release from synaptosomes of the medulla oblongata of the spontaneously hypertensive rat.
The release of 3H-noradrenaline (3H-NA) evoked by high-K+ (15 mM) was studied in synaptosomes isolated from the medulla oblongata of the normotensive Wistar-Kyoto and spontaneously hypertensive male rat (14 weeks old) using a superfusion apparatus. Based on concentration-response curves clonidine was shown to have a reduced ability to inhibit 3H-NA release in synaptosomes isolated from the spontaneously hypertensive rat (SHR) versus the normotensive rat. Furthermore, only a high concentration of NPY (100 nM) had the ability to enhance the inhibitory effects of clonidine on 3H-NA release in synaptosomes isolated from the medulla oblongata of the SH male rat, while 1 nM of NPY was effective in synaptosomes isolated from the medulla oblongata of the normotensive Wistar-Kyoto rat. These results may indicate a reduced presynaptic alpha 2-adrenoceptor and NPY receptor function to inhibit 3H-NA release from NA and/or adrenaline (A) nerve terminals in the medulla oblongata of the adult 14 weeks old SHR.
Martire
M
M
Department of Pharmacology, Catholic University, Rome, Italy.
Fuxe
K
K
Pistritto
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G
Preziosi
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P
Agnati
L F
LF
D000818:Animals; D003000:Clonidine / Q000494:pharmacology*; D008297:Male; D008526:Medulla Oblongata / Q000187:drug effects / Q000378:metabolism* / Q000503:physiopathology; D009478:Neuropeptide Y / Q000494:pharmacology*; D009638:Norepinephrine / Q000493:pharmacokinetics*; D051381:Rats; D011918:Rats, Inbred SHR / Q000378:metabolism*; D011919:Rats, Inbred Strains / Q000378:metabolism*; D013574:Synaptosomes / Q000187:drug effects / Q000378:metabolism
D009478:Neuropeptide Y; D003000:Clonidine; D009638:Norepinephrine