| Summary: | 碩士 === 國立成功大學 === 藥理學研究所 === 84 === It is well known that the rat urinary bladder possesses an non-
adrenergic, non-cholinergic ( NANC) innervation. However, the
neurotransmitter for this NANC neurotransmission is still
contro- versial and is the main interest of our research.The
rat detrusor muscle strips were studied in organ bath in vitro
and contraction were induced by electric-field stimulation
(EFS). The amplitude of contraction increased as the frequency
was increased.The frequency-dependent contractions were almost
completely abolished by tetrodotoxin (TTX), indicating that the
response to EFS was predominantly neurogenic. The NANC
contraction was obtained in the presence of the four autonomic
nerve blockers (atropine, guanethidine, phentolamine and
propranolol). The NANC component constituted a greater portion
of the contraction at low frequency than that at high
frequency. Desensitization induced by a.b-MeATP , a P2x
receptor agonist, reduced the NANC contractions evoked by a
constant stimulating frequency 3Hz (EF50).Meanwhile, this NANC
response was abolished mostly in ATP desensitized sample.
Adenosi -ne has a similar activity asATP. In addition, this
NANCcontrac -tion was also abolished mostly by P2 receptor
blockers suramin and P2x receptor blocker PPADS, at
concentrations sufficient to block a.b-MeATP-induced
contraction. It is suggested that this NANC contraction in
urinary bladder might be one of the pur- inergic actions of ATP.
Dipyridamole, a adenosine uptake inhibitor ,inhibited NANC
contraction at concentrations which influenced the action of a,
b-MeATP. DPCPX, a A1 adenosine receptor blocker, did not affect
NANC contraction even at high concentration. The adenyl purines
released by EFS from nerve were detected by HPLC and the amount
of ATP was more than adenosine.Therefore,combining measurement
of adenyl purines release and the results of fun- ctional
studies,the present study suggests that ATP plays an important
role in NANC neurotransmission of the rat bladder.
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