Distribution and properties of excitatory and inhibitory junction potentials in circular muscle of the XXXX stomach.

@entity2997 @entity308 @entity840 @entity1617 @entity3897 @entity2607 @entity1339 @entity934
In the presence of @entity2997 (10(-6)-5 X 10(-6) M), transmural nerve stimulation evoked an excitatory junction potential (e.j.p.) in the fundus region and an inhibitory junction potential (i.j.p.) in the antrum region of the circular muscle of the @entity840 stomach. The e.j.p. was blocked by @entity3897 (over 2 X 10(-7) M) while the i.j.p. was blocked by apamin (10(-7) M) but not by adrenergic or cholinergic receptor antagonists. Therefore the i.j.p. may be non-adrenergic and non-cholinergic in nature. In the presence of @entity3897 , nerve stimulation evoked the non-adrenergic, non-cholinergic i.j.p. in both regions of the stomach. In the antrum region, single stimuli enhanced the subsequent slow wave by 1.1-1.3 times, in comparison with that before the stimuli, and this effect was blocked by @entity3897 (over 2 X 10(-7) M). The reversal potential for the e.j.p. was about -18 mV, while that for the i.j.p. was -87 mV in the atropinized fundus and -89 mV in the antrum region. In the fundus region, a pair of nerve stimulations with short intervals (1-4 s) reduced ( @entity308 ) and with long intervals (5-20 s) enhanced (facilitation) the second e.j.p. or the i.j.p. After inhibition of @entity934 esterase (AChE) by @entity2607 or @entity1339 , nerve stimulation evoked an enhanced e.j.p., and then produced a sustained depolarization with a duration of 3-5 s in the fundus region, while the amplitude of slow waves after nerve stimulation was further enhanced in the antrum region. These effects of anticholinesterases were blocked by @entity3897 . Exogenously applied @entity934 ( @entity1617 ) depolarized the smooth muscle membrane; the threshold concentration of @entity1617 was about 1000 times higher in the antrum region (10(-6) M) than in the fundus region (10(-9) M). It is concluded that in the @entity840 stomach, regional differences in junction potentials may be due to different sensitivities of @entity1617 receptor, and that nerve stimulation evokes a cholinergic e.j.p. in a high-sensitivity region (fundus) and a non-adrenergic, non-cholinergic i.j.p. in a low-sensitivity region (antrum).
