L-dopa potentiates presynaptic inhibitory alpha 2-adrenoceptor- but not facilitatory angiotensin II receptor-mediated modulation of noradrenaline release from rat hypothalamic slices.
L-dopa is a potentiator for presynaptic beta-adrenoceptors. We studied whether L-dopa potentiates the activities of other presynaptic receptors to modulate the evoked noradrenaline (NA) release in rat hypothalamic slices. UK14304 (0.1-1 microM), a selective alpha 2-agonist, concentration-dependently inhibited NA release. Noneffective 10 pM L-dopa potentiated the UK14304-induced inhibition. This potentiation was selectively antagonized by 1 nM L-dopa methyl ester, a competitive L-dopa antagonist, while yohimbine antagonized both the inhibition by UK14304 alone and its potentiation by L-dopa. However, 10 pM L-dopa produced no effect on angiotensin II (0.1-1 nM)-induced facilitation. L-dopa potentiates activities of presynaptic beta- and alpha 2-adrenoceptors but not those of angiotensin II receptors on rat hypothalamic NA neurons.
Sato
K
K
Department of Anaesthesiology, Yokohama City University School of Medicine, Japan.
Okumura
F
F
Goshima
Y
Y
Miyamae
T
T
Misu
Y
Y
D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000804:Angiotensin II / Q000378:metabolism*; D000818:Animals; D000068438:Brimonidine Tartrate; D007031:Hypothalamus / Q000187:drug effects / Q000378:metabolism*; D066298:In Vitro Techniques; D007980:Levodopa / Q000031:analogs & derivatives / Q000494:pharmacology*; D008297:Male; D009638:Norepinephrine / Q000378:metabolism*; D011810:Quinoxalines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects*; D011945:Receptors, Angiotensin / Q000187:drug effects*; D013569:Synapses / Q000187:drug effects; D015016:Yohimbine / Q000494:pharmacology
D000316:Adrenergic alpha-Agonists; D011810:Quinoxalines; D011942:Receptors, Adrenergic, alpha; D011945:Receptors, Angiotensin; D000804:Angiotensin II; D015016:Yohimbine; D007980:Levodopa; D000068438:Brimonidine Tartrate; C035420:levodopa methyl ester; D009638:Norepinephrine