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Title: Inhibitory effect of GABA on sympathetic neurotransmission in rabbit ear artery. Author: Manzini S, Maggi CA, Meli A. Journal: Arch Int Pharmacodyn Ther; 1985 Jan; 273(1):100-9. PubMed ID: 2988467. Abstract: GABA 100 microM inhibited neurogenic vasoconstrictor responses elicited in rabbit ear artery by field stimulation at various frequencies. GABA was ineffective both on resting tone and on noradrenaline (0.05-5 microM)- and high-K+ (24-54 mM)-induced tonic contraction. GABA effectiveness against field stimulation-induced vasoconstriction was inversely related to the frequency of stimulation. This action of GABA was mimicked by a selective GABAB agonist, such as baclofen (100 microM), but not by selective GABAA agonists as muscimol (100 microM) and homotaurine (100 microM). The selective GABAB antagonists 5-aminovaleric acid (1 mM) and homotaurine (100 microM) completely suppressed the inhibitory effect of GABA on field stimulation-induced vasoconstrictions. GABA action was partially reversed also by the selective GABAA antagonist picrotoxin (100 microM); however, this drug "per se" determined an increase in amplitude of field stimulation-induced contractions which in turn could have determined the minor effect of GABA. As a whole these data suggest that GABA can inhibit sympathetic neurotransmission in rabbit ear artery through the stimulation of a prejunctional receptor of the GABAB subtype.[Abstract] [Full Text] [Related] [New Search]