Cholinergic neurotransmission plays a major role in the postganglionic nerve evoked contractile respons of the urinary bladder, but there is atropine-resistnat contraction that is not completely blocked by atropine and may be related with
nonadrenergic-noncholinergic (NANC) neurotransmission. Among the NANC neurotransmission, adenosine triphosphate (ATP) is an important transmnitter in an important transmitter in purinergic neurotransmission which is known to many vertebrates
including
human beings.
The aim of this study is to determine the role and existence of purinergic neurotransmission in the canine detrusor muscle. In vivtro contractile responses to electrical stimulation after pretreatment with atropine were measured in the presence
of
purinergic antagonist such as theophylline, β, γ-methylene ATP and verapamil. Field stimulation (frequency 0.5-40 Hz; pulse width 1ms; 10V square wave) produced a contraction that was abolished by tetrodotoxin (0.1μM) and reduced by 42.5%
after
atropine (10μM) pretreatment. The contractile response was reduced by 44.1%, 30.3% and 60.1% after the treatment of theophylline (1μM, 10μM and 100μM) in the presence of atropine, 11.1%, 22.7% and 30.3% after the treatment of β, γ-methylene
ATP
(5μM, 50μM and 500μM) and 17.6%, 39.4% and 60.1% after the treatment of verapamil (0.1μM, 1μM and 10μM) at 20 Hz frequency. These reduced contractile responses were statistically significant (p<0.05), especially in higher concentration. and
relatively frequency-dependent and verapamil decreased the contractile response most significantly.
These data demonstrat that purinergic neurotransmission is related to the contraction of canine detrusor muscle. On the other hand contractile responses were persisted after pretreatment of higher dose antagonist, which suggests that another
mechanism
such as peptidergic mechanism be related to the contraction of canine detrusor muscle.
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