Premium
Signal transduction of cannabinoid CB 1 receptors in a smooth muscle cell line
Author(s) -
Begg M.,
Baydoun A.,
Parsons M. E.,
Molleman A.
Publication year - 2001
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.2001.0095j.x
Subject(s) - iberiotoxin , cannabinoid receptor type 2 , cannabinoid receptor , chemistry , adenylyl cyclase , agonist , receptor , biology , endocrinology , medicine , microbiology and biotechnology , biochemistry , potassium channel
1 The effects of cannabinoid (CB) receptor stimulation on membrane currents in single cells from the Syrian hamster vas deferens cell line DDT 1 MF‐2 were investigated using the whole cell patch clamp technique. 2 The CB receptor agonist CP55,940 evoked a concentration‐dependent transient outward current. The selective CB 1 receptor ligand SR141716 (1 μ m ), but not the selective CB 2 receptor ligand SR144528 (1 μ m ), inhibited the outward current. Pertussis toxin (100 ng ml −1 for 20 h) completely abolished the outward current. 3 Western blotting with an antibody against the rat (r)CB 1 receptor showed a band characteristic for the CB 1 receptor around 63 kDa in DDT 1 MF‐2 cells. 4 The reversal potential for the outward current measured using a voltage ramp protocol was −84 ± 5 mV. The current was inhibited by the Ca 2+ ‐dependent K + channel blockers iberiotoxin (10 n m ) and charybdotoxin (10 n m ). 5 Removal of Ca 2+ from the bathing solution, or the addition of 0.1 m m Cd 2+ completely abolished the outward current evoked by 10 μ m CP55,940. 6 The sarcoplasmic Ca 2+ pump inhibitor thapsigargin reduced the outward current evoked by 10 μ m CP55,940 in a concentration‐dependent manner. 7 The mitogen‐activating protein kinase (MAP kinase) inhibitor PD98059, but not the phospholipase C inhibitor U73122, inhibited the outward current evoked by 10 μ m CP55,940. 8 The adenylyl cyclase inhibitor SQ22,536 (100 μ m ) and 8‐Br‐cyclic AMP (10 μ m ) significantly reduced the outward current evoked by 10 μ m CP55,940. 9 Our data suggest that CB 1 receptor stimulation in DDT 1 MF‐2 cells leads to activation of a large conductance Ca 2+ ‐dependent K + channel through a G i /G o protein‐mediated rise in [Ca 2+ ] i , for which both inhibition of adenylyl cyclase and activation of MAP kinase are required. In addition, the cannabinoid‐induced increase in [Ca 2+ ] i is likely to arise from capacitive Ca 2+ entry.