Autonomous Activity in the Isolated Guinea Pig Bladder

Abstract

Phasic changes in pressure have been reported to occur in the bladder which are not associated with micturition. Spontaneous intravesical pressure changes can be recorded from bladders in vitro or bladders in vivo isolated from the central nervous system suggesting that the bladder itself is capable of autonomous activity. Experiments using isolated cells and muscle strips indicate that the smooth muscle can generate spontaneous activity. Whether this is the origin of phasic changes in the intact organ remains unknown. The present study set out to establish the presence and characteristics of autonomous activity in the isolated guinea pig bladder. Multiple-point motion analysis and concurrent intravesical pressure recording were used to identify and quantify spontaneous and evoked activity. Highly complex autonomous activity was observed in unstimulated bladders. This activity comprised localised micro-contractions in single or multiple discrete regions, waves of activity and micro-stretches. Low-amplitude phasic 'micro-transients' were seen in the intravesical pressure trace in association with micro-contractions. Incremental increases in the intravesical volume recruited additional areas of activity. Atropine and tetrodotoxin had no effect on the micro-transients or micro-contractions. Exposure to the muscarinic agonist arecaidine (10-300 nM) initially increased the incidence of micro-contractions which subsequently became co-ordinated into phasic pressure rises and contraction waves, interspersed with periods of total quiescence. The findings describe the generation and co-ordination of autonomous activity in the bladder wall and also demonstrate complex phasic activity. This approach has shown the importance of assessing the integrative properties of the entire organ in studies of the physiology and patho-physiology of the bladder.

Evidence of increased centrally enhanced bladder compliance with ageing in a mouse model

“…In ex vivo intact bladder models, motion and intravesical pressure analysis shows tetrodotoxin and atropine-resistant low amplitude (≈ 1 cmH2O) phasic contractile activity occurring at a frequency of 0.01-0.1 Hz [14]. Similar micromotional activity has been detected during human bladder filling, and is more marked in those with increased sensation [15].…”

“…NVCs could be evidence of intrinsic activity amplified by non-neuronal release of neurotransmitters with increasing volume. Muscarinic stimulation increases the amplitude of autonomous contractions [14] and therefore afferent activity; hypogastric sympathetic efferent activity is responsive to bladder filling [28], thus producing a reflex sympathetically mediated relaxation. Centrally induced 'pre-voiding' NVC contractions become evident in the mouse as the autonomic balance shifts towards the parasympathetic dominance of voiding.…”

A gap junction blocker inhibits isolated whole bladder activity in normal rats and rats with partial bladder outlet obstruction

“…Spontaneous changes of intravesical pressure can be recorded from an isolated whole bladder in the absence of central nervous system input (6,16). In the present study, whole bladders obtained from both intact and BOO rats also showed autonomous activity when maintained in Krebs solution at 26°C.…”

“…myocardium is also Connexin43 (8), it is impossible to administer 18alpha-glycyrrhetinic acid systemically to block intercellular communication in the bladder. Experiments on isolated whole bladders have shown that the bladder smooth muscle displays spontaneous activity in the absence of central nervous system input (6,16). In the present study, we examined the influence of 18alpha-glycyrrhetinic acid on isolated whole bladders harvested from rats with or without partial BOO, and compared its effects with those of propiverine hydrochloride (a muscarinic antagonist).…”

The electrical activity of the bladder after isolation

“…При этом возможно также объединение отдельных потенциалов в группы в виде вспышек активности, которе ассоциируются с последующей контрактурой [6,7,8]. Описанная спонтанная электрическая активность наблюдается также в изолированном мочевом пузыре, в его мышечных препаратах или даже в единичных клетках [9,10].…”