Facilitation of transmitter release in the urinary bladders of neonatal and adult rats via alpha1-adrenoceptors.
Age-dependent changes in the effects of the alpha1-adrenoceptor agonist, phenylephrine were investigated on neurally evoked contractile responses and basal tone in smooth muscle strips from rat urinary bladder. Phenylephrine facilitated the neurogenic contractions in both neonatal and 7-month-old adult rats. However, phenylephrine increased the basal tone in adult but not neonatal rats. In adult rats, phenylephrine-induced facilitation of neurally evoked contractions occurred before and after the block of cholinergic contractions with 1 microM atropine. In adult rats, the phenylephrine facilitation was reduced at stimulation parameters (20 Hz, 80 shocks and maximal voltage) which activated muscarinic receptor mediated facilitation of acetylcholine release. The results indicate that pre-synaptic alpha1-adrenoceptors facilitate the release of both acetylcholine and the non-cholinergic non-adrenergic transmitter. In summary, alpha1-adrenoceptor-mediated facilitation is less expressed when muscarinic M1 receptor mediated facilitation is functioning; pre-junctional alpha1-adrenoceptors are present in the bladder of both neonatal and adult rats, whereas post-junctional alpha1-adrenoceptors are expressed only in older adult rats.
Yamamoto
T
T
Department of Pharmacology, University of Pittsburgh, W1354 Biomedical Science Center, Pittsburgh, PA 15261, USA.
Ghosh
R
R
De Groat
W C
WC
Somogyi
G T
GT
D000109:Acetylcholine / Q000378:metabolism; D000316:Adrenergic alpha-Agonists / Q000494:pharmacology*; D000367:Age Factors; D000818:Animals; D000831:Animals, Newborn; D001285:Atropine / Q000494:pharmacology; D005260:Female; D018727:Muscarinic Antagonists / Q000494:pharmacology; D009130:Muscle, Smooth / Q000187:drug effects* / Q000502:physiology; D010656:Phenylephrine / Q000494:pharmacology*; D051381:Rats; D043643:Receptor, Muscarinic M1; D018340:Receptors, Adrenergic, alpha-1 / Q000187:drug effects* / Q000502:physiology; D011976:Receptors, Muscarinic / Q000187:drug effects / Q000502:physiology; D001743:Urinary Bladder / Q000187:drug effects* / Q000502:physiology
D000316:Adrenergic alpha-Agonists; D018727:Muscarinic Antagonists; D043643:Receptor, Muscarinic M1; D018340:Receptors, Adrenergic, alpha-1; D011976:Receptors, Muscarinic; D010656:Phenylephrine; D001285:Atropine; D000109:Acetylcholine