Functional and immunohistochemical characterization of CB1 and CB2 receptors in rat bladder.
OBJECTIVE
To determined the localization of CB(1) and CB(2) receptors in rat bladder and investigate the effect of a mixed CB(1)/CB(2) receptor agonist, ajulemic acid (AJA), on chemically evoked release of the sensory neuropeptide calcitonin gene-related peptide (CGRP).


METHODS
Whole rat bladders were incubated in a series of tissue baths containing physiologic salt solution to measure baseline CGRP release by enzyme immunoassay. Capsaicin (30 nM) and adenosine triphosphate (10 muM) were used to provoke CGRP release in the presence or absence of AJA. Specificity of AJA for CB(1) and CB(2) receptors was determined using antagonists. Localization was determined by immunofluorescence for CB(1) and CB(2) receptors in fixed bladders.


RESULTS
Immunofluorescence showed the localization of CB(1) and CB(2) receptors in the bladder. Mean baseline CGRP release was 605 +/- 62 pg/g of bladder weight, and AJA had no effect on CGRP release. The addition of adenosine triphosphate/capsaicin significantly increased the CGRP release over baseline, by 44% (P < .05), and AJA application significantly decreased CGRP release, by 29% compared with controls (P < .05). The CB(1) and CB(2) antagonists AM 251 and AM 630, respectively, reversed the blunting effect of AJA on evoked CGRP release, resulting in an increase of 40% and 38% over baseline, respectively.


CONCLUSIONS
CB(1) and CB(2) receptors are localized in the urothelium of rat bladder, and application of AJA inhibits the evoked release of CGRP by acting on CB(1) and CB(2) receptors. These findings identify a potential new pathway for study in the evaluation and treatment of painful bladder syndrome/interstitial cystitis.
Hayn
Matthew H
MH
Department of Urology, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania 15213, USA.
Ballesteros
Inmaculada
I
de Miguel
Fernando
F
Coyle
Christian H
CH
Tyagi
Shachi
S
Yoshimura
Naoki
N
Chancellor
Michael B
MB
Tyagi
Pradeep
P
D000818:Animals; D015740:Calcitonin Gene-Related Peptide / Q000378:metabolism; D013759:Dronabinol / Q000031:analogs & derivatives / Q000494:pharmacology; D005260:Female; D007211:Indoles / Q000494:pharmacology; D010880:Piperidines / Q000494:pharmacology; D011720:Pyrazoles / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D043884:Receptor, Cannabinoid, CB1 / Q000819:agonists / Q000037:antagonists & inhibitors / Q000378:metabolism*; D043885:Receptor, Cannabinoid, CB2 / Q000819:agonists / Q000037:antagonists & inhibitors / Q000378:metabolism*; D046509:Tissue Culture Techniques; D001743:Urinary Bladder / Q000187:drug effects / Q000378:metabolism*
D007211:Indoles; D010880:Piperidines; D011720:Pyrazoles; D043884:Receptor, Cannabinoid, CB1; D043885:Receptor, Cannabinoid, CB2; C103505:AM 251; D013759:Dronabinol; D015740:Calcitonin Gene-Related Peptide; C471849:lenabasum; C094023:iodopravadoline