Neuroeffector transmission in the guinea-pig internal anal sphincter: an electrical and mechanical study

Neuronal mediators of inhibitory junction potentials and relaxation in the guinea‐pig internal anal sphincter.

“…10mV -50 mV RB2 (100 /SM) also reduced the amplitude of the apaminsensitive IJP component but hyperpolarized the membrane and lowered tone irreversibly; these latter effects, rather than the antagonist itself, could have accounted for the reduction in IJP amplitude (data not shown). These results suggested that purinoceptors, probably P2Y (Lim & Muir, 1986), were involved in the fast apaminsensitive component of the IJP. In support of this view, ATP itself applied either by injection (1 mM) or by pressure ejection (0 1 for -27), examined in this study.…”

“…ATP, or a closely related analogue, appears to mediate the apamin-sensitive component. Exogenous ATP produced a concentration-dependent hyperpolarization which resembled the IJP in time to peak and duration more closely than VIP, PACAP(1-27) (data not shown) or, indeed, any other peptide investigated (Lim & Muir, 1986;Rae & Muir, 1994). Indeed there is little evidence to support the involvement of VIP in the IJP in the gpIAS.…”

“…In spite of reservations as to the specificity of both suramin (McConalogue et al 1994) and RB2, both continue to be used as purinoceptor antagonists in the absence of more specific compounds (see Manzini et al 1986;Hoyle et at. 1990 (Lim & Muir, 1986). This evidence is tempered by the ability of EFS to produce IJPs in the gpIAS following prolonged application of ATP when the response to the nucleotide was abolished (Lim & Muir, 1986 -channel blocker TTX.…”

Purinergic signalling in the gastrointestinal tract and related organs in health and disease

“…Relaxation and hyperpolarisation during electrical field stimulation of the mouse internal anal sphincter was mediated by the cotransmitters ATP and NO [383]. ATP hyperpolarised and relaxed the internal anal sphincter of guinea pig [440,562] and rat [171]. P2Y 1 receptors mediated the effects and both apamin-sensitive K + channels and apamininsensitive conductances were involved in hyperpolarisation and relaxation of the mouse internal anal sphincter [466].…”

Lack of nitrate tolerance in isosorbid dinitrate- and sodium nitroprusside-induced relaxation of rabbit internal anal sphincter

“…Prominent nonadrenergic noncholinergic (NANC) innervations of IAS have been demonstrated [1][2][3] . In vivo and in vitro studies showed that the NANC neurons caused relaxation of the IAS [4][5][6] . The tonic resting pressure of IAS is called "anal resting pressure".…”