In vitro alpha-adrenoceptor autoradiography of the urethra and urinary bladder of the female pig, cat, guinea-pig and rat.
OBJECTIVE
The aim of this study was to investigate the distribution of alpha1- and alpha2-adrenoceptors in the urethra and urinary bladder of the female pig, cat, guinea-pig and rat.


METHODS
The binding distributions of an alpha1-adrenoceptor ligand (3H-prazosin) and an alpha2-adrenoceptor ligand (3H-rauwolscine) were determined using in vitro autoradiography. Autoradiograms were analysed by combining computer-based image analysis and light microscopy.


RESULTS
In the pig, guinea-pig and rat urethra 3H-prazosin binding was highest in the muscle layer. In the cat urethra 3H-prazosin binding could not be analysed due to a negative chemography artefact. In the pig, cat and guinea-pig urethra 3H-rauwolscine binding was highest in the urothelium, followed by the sub-mucosa, with low levels in muscle. Little 3H-rauwolscine binding was observed in the rat urethra. In the urinary bladder of all species 3H-prazosin binding was low. In the rat bladder, binding was higher in the trigone than in the dome. In the pig, cat and guinea-pig bladder 3H-rauwolscine binding was highest in the mucosa. with little binding in muscle or lamina propria. In the rat bladder, there was little binding and no regional differences.


CONCLUSIONS
Alpha1-adrenoceptors were predominantly located in urethral smooth muscle, indicating their contractile importance in maintaining continence. Alpha2-Adrenoceptors were present in the urethral submucosa and bladder mucosa, but not in muscle, suggesting a role in regulation of blood flow, urethral lubrication and tumescence, but not in contraction.
Monneron
M C
MC
Department of Pharmacology, Pharmacia and Upjohn, Uppsala, Sweden.
Gillberg
P G
PG
Ohman
B
B
Alberts
P
P
D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000818:Animals; D001345:Autoradiography; D001665:Binding Sites; D002415:Cats; D005260:Female; D006168:Guinea Pigs; D009130:Muscle, Smooth / Q000378:metabolism; D011224:Prazosin / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D011941:Receptors, Adrenergic / Q000378:metabolism*; D013552:Swine; D014521:Urethra / Q000378:metabolism*; D001743:Urinary Bladder / Q000378:metabolism*; D015016:Yohimbine / Q000494:pharmacology
D000317:Adrenergic alpha-Antagonists; D011941:Receptors, Adrenergic; D015016:Yohimbine; D011224:Prazosin