Effects of cannabinoid receptor agonists on neuronally-evoked contractions of urinary bladder tissues isolated from rat, mouse, pig, dog, monkey and human

Abstract

This study investigated the cannabinoid receptor, known to inhibit neuronally-evoked contractions of the mouse isolated urinary bladder, in bladder sections isolated from mouse, rat, dog, pig non-human primate or human. The CB(1)-like pharmacology of the cannabinoid receptor in mouse isolated bladder observed previously was confirmed in this study by the rank order of agonist potencies: CP 55940>/=WIN 55212-2>HU 210>JWH 015>anandamide, the high affinity of the CB(1) selective antagonist, SR 141716A (apparent pK(B) 8.7), and the low affinity of the CB(2) antagonist, SR 144528 (apparent pK(B)<6.5). In these studies, SR 141716A (10-100 nM) significantly potentiated electrically-evoked contractions in this tissue by an undetermined mechanism. A similar rank order of agonist potencies was determined in rat isolated bladder sections (CP 55, 940> or =WIN 55212-2>JWH 015). In this tissue, the maximal inhibitory effect of all agonists was lower than in the mouse bladder. Indeed, the effects of both HU 210 and anandamide were too modest to quantify potency accurately. In the rat isolated bladder, SR 141716A (30 nM) or SR 144528 (100 nM), reversed the inhibitory effect of WIN 55212-2 (apparent pK(B) = 8.4 and 8.0, respectively) or JWH 015 (apparent pK(B) = 8.2 and 7.4, respectively). These findings may demonstrate pharmacological differences between the rat and mouse orthologues of the CB(1) receptor. Alternatively, they may be attributed to a mixed population of CB(1) and CB(2) receptors that jointly influence neurogenic contraction of the rat bladder, but cannot be differentiated without more selective ligands. WIN 55212-2 had no effect on electrically-evoked contractions of bladder sections isolated from dog, pig, cynomolgus monkey and human. These findings suggest that the effect of cannabinoid agonists to inhibit neurogenic contraction of the mouse and rat bladder is not conserved across all mammalian species.

Figure 1

Inhibitory effect of WIN 55212, CP 55940, HU 210, anandamide and JWH 015 on electrically-evoked contractions in mouse (A) and rat (B) urinary bladder. Data are the means±s.e.mean of replicate determinations from tissues isolated from 3–6 animals.

Figure 2

Electrically-evoked contractions of mouse isolated urinary bladder. Contractions were evoked by electrical stimulation over 2 min intervals (8 V, 12 pulses s⁻¹, 0.5 ms pulse width, 0.1 trains s⁻¹) in sections of mouse isolated bladder before and after 1 h incubation with (A) SR 141716A (30 nM) or (B) DMSO (0.005% v v⁻¹).

Figure 3

Antagonism of WIN 55212-2 -mediated effect by SR 141716A (30 nM), SR 144528 (100 or 300 nM) and AM 630 (3 μM) in mouse (A) and rat (B) urinary bladder. Data are the mean±s.e.mean of replicate determinations from tissues isolated from 4–6 animals.

Figure 4

Antagonism of JWH 015-mediated effect by SR 141716A (100 nM) and SR 144528 (100 nM) in mouse (A) and rat (B) isolated bladder. Data are the means±s.e.mean of replicate determinations in tissues from 4–6 animals.

Figure 5

Effect of WIN 55212-2 (3 μM) or SR 141716A (30 nM) on contractile responses to α,β-methylene ATP or carbachol (control responses) in isolated bladder sections from the mouse (A,B) and rat (C,D). Data are the mean±s.e.mean from 4–6 replicates.

Figure 6

Effect of WIN 55212-2 (3 μM) on frequency response curves in isolated bladder tissue from mouse (A), rat (B), dog (C), pig (D), non-human primate (E), human (F). Data are the mean±s.e.mean from 4–7 replicates, significant difference between control and WIN 55212-2 (3 μM)-treated tissues indicated by ^*(P<0.05) and ^**(P<0.01).

Figure 7

Effect of co-administration of atropine (0.3 μM; A,B) or α,β-methylene ATP (3 μM; B,D) with WIN 55212-2 (3 μM) on frequency-response curves in mouse (A,B) or rat (C,D) isolated urinary bladder. Significant difference between treatment with atropine or α,β-methylene ATP alone or in combination with WIN 55212-2, determined by Student's t-test, is indicated by ^*(P<0.05) and ^**(P<0.01). Data are the mean±s.e.mean of 4–6 replicates.