Are the alpha 2-adrenoceptors in the noradrenaline cell body region of physiological significance?
Preganglionic stimulation of the cervical sympathetic increased the content of 3,4-dihydroxyphenylacetic acid (DOPAC) in the superior cervical ganglion of rats treated with the dopamine beta-hydroxylase inhibitor FLA-63. It also increased and decreased the concentrations of dopamine and noradrenaline, respectively, in the salivary gland. The effects were partially inhibited by the alpha 2-adrenoceptor agonist clonidine via a yohimbine-sensitive mechanism. The alpha 2-adrenoceptor antagonist yohimbine by itself did not enhance the stimulation-evoked increase in ganglionic DOPAC, but it markedly potentiated the stimulation-evoked changes in dopamine and noradrenaline in the salivary gland. The results indicate that there are inhibitory alpha 2-adrenoceptors both in the somatodendritic and in the axon terminal region of the noradrenaline neurons but that only the alpha 2-receptors of the axon terminals are physiologically stimulated.
D015102:3,4-Dihydroxyphenylacetic Acid / Q000378:metabolism; D000818:Animals; D001369:Axons / Q000378:metabolism; D003000:Clonidine / Q000494:pharmacology; D004298:Dopamine / Q000378:metabolism; D005727:Ganglia, Spinal / Q000378:metabolism; D066298:In Vitro Techniques; D008297:Male; D009638:Norepinephrine / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D011942:Receptors, Adrenergic, alpha / Q000502:physiology*; D012469:Salivary Glands / Q000378:metabolism; D013564:Sympathetic Nervous System / Q000166:cytology / Q000502:physiology*; D015016:Yohimbine / Q000494:pharmacology
D011942:Receptors, Adrenergic, alpha; D015102:3,4-Dihydroxyphenylacetic Acid; D015016:Yohimbine; D003000:Clonidine; D004298:Dopamine; D009638:Norepinephrine