Modulation of the release of [3H]norepinephrine from the base and body of the rat urinary bladder by endogenous adrenergic and cholinergic mechanisms.
Modulation of [3H]NE release was studied in rat urinary bladder strips prelabeled with [3H]NE. [3H]NE uptake occurred in strips from the bladder base and body, but was very prominent in the base where the noradrenergic innervation is most dense. Electrical field stimulation markedly increased [3H]NE outflow from the superfused tissue. The quantity of [3H]NE release was approximately equal during three consecutive periods of stimulation. Activation of presynaptic muscarinic receptors by 1.0 microM oxotremorine reduced [3H]NE release to 46% of the control. Atropine (1 microM) blocked the effect of oxotremorine and increased the release to 147% of predrug control levels. Activation of presynaptic alpha-2 adrenoceptors by 1 microM clonidine reduced [3H]NE release to 55% of control. Yohimbine blocked the action of clonidine and increased the release to 148% of control. The release of [3H]NE from the bladder base and body was increased by both 1 microM atropine (to 167% and 174% of control, respectively) and 1 microM yohimbine (to 286% and 425% of control, respectively). Atropine and yohimbine administered in combination had similar facilitatory effects as when administered alone. We conclude that the release of [3H]NE from adrenergic nerve endings in electrically stimulated bladder strips is modulated via endogenous transmitters acting on both muscarinic and alpha-2 adrenergic presynaptic receptors and that the latter provide the most prominent control.
Somogyi
G T
GT
Department of Pharmacology, University of Pittsburgh, Pennsylvania.
de Groat
W C
WC
D000109:Acetylcholine / Q000378:metabolism; D000818:Animals; D003000:Clonidine / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D009638:Norepinephrine / Q000378:metabolism*; D010095:Oxotremorine / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects / Q000502:physiology*; D011976:Receptors, Muscarinic / Q000187:drug effects / Q000502:physiology*; D014316:Tritium; D001743:Urinary Bladder / Q000378:metabolism*; D015016:Yohimbine / Q000494:pharmacology
D011942:Receptors, Adrenergic, alpha; D011976:Receptors, Muscarinic; D014316:Tritium; D015016:Yohimbine; D010095:Oxotremorine; D003000:Clonidine; D000109:Acetylcholine; D009638:Norepinephrine