Presynaptic GABAB receptors and the regulation of [3H]noradrenaline release from rat anococcygeus muscle.
The release of preaccumulated [3H]noradrenaline from the isolated rat anococcygeus muscle, a tissue endowed with a rich noradrenergic innervation, was investigated. Field stimulation produced a marked, calcium-dependent enhancement in release, which could be substantially inhibited by the inclusion of low concentrations of GABA or (-)-baclofen (but not the (+)-isomer) in the bathing medium. Classical GABAA site agonists such as muscimol or 3-aminopropanesulphonic acid were inactive, or only weakly so. Picrotoxin and bicuculline were unable to antagonise the effects of GABA or baclofen on [3H]noradrenaline release, although 5-aminovalerate was effective. These data provide further evidence for the existence of GABAB receptors associated with presynaptic noradrenergic terminals in the rat anococcygeus muscle.
D000818:Animals; D001418:Baclofen / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D018756:GABA Antagonists; D066298:In Vitro Techniques; D008297:Male; D009132:Muscles / Q000378:metabolism*; D009638:Norepinephrine / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D011956:Receptors, Cell Surface / Q000502:physiology*; D011963:Receptors, GABA-A; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology
D018756:GABA Antagonists; D011956:Receptors, Cell Surface; D011963:Receptors, GABA-A; D005680:gamma-Aminobutyric Acid; D001418:Baclofen; D009638:Norepinephrine