title: Neurochemical evidence for two types of presynaptic alpha 2-adrenoceptors.
abstract: Neurochemical and pharmacological evidence has been obtained that noradrenergic varicosities (in mouse and rat vas deferens) and cholinergic varicosities (in the Auerbach's plexus) contain heterogenous alpha 2-adrenoceptors through which the release of [3H]noradrenaline and [3H]acetylcholine can be modulated. The quantitative data also support the hypothesis that different noradrenaline and xylazine sensitive alpha 2-adrenoceptors are present prejunctionally in the vas deferens and Auerbach's plexus preparations. Prazosin, although it has a presynaptic inhibitory effect on alpha 2-adrenoceptors of noradrenergic axon terminals, has no effect on cholinergic axon terminals. These data suggest that there are two different types of alpha 2-adrenoceptors at the presynaptic axon terminals.
mesh_terms: D000320:Adrenergic Fibers / Q000032:analysis; D000818:Animals; D002799:Cholinergic Fibers / Q000032:analysis; D006168:Guinea Pigs; D008297:Male; D009130:Muscle, Smooth / Q000032:analysis*; D009197:Myenteric Plexus / Q000032:analysis*; D009638:Norepinephrine / Q000494:pharmacology; D011224:Prazosin / Q000494:pharmacology; D051381:Rats; D011942:Receptors, Adrenergic, alpha / Q000032:analysis* / Q000502:physiology; D014649:Vas Deferens / Q000032:analysis*; D014991:Xylazine / Q000494:pharmacology
chemical_list: D011942:Receptors, Adrenergic, alpha; D014991:Xylazine; D009638:Norepinephrine; D011224:Prazosin