Characterization of mouse neuro‐urological dynamics in a novel decerebrate arterially perfused mouse (DAPM) preparation

Abstract

AimTo develop the decerebrate arterially perfused mouse (DAPM) preparation, a novel voiding model of the lower urinary tract (LUT) that enables in vitro‐like access with in vivo‐like neural connectivity.MethodsAdult male mice were decerebrated and arterially perfused with a carbogenated, Ringer's solution to establish the DAPM. To allow distinction between central and peripheral actions of interventions, experiments were conducted in both the DAPM and in a “pithed” DAPM which has no brainstem or spinal cord control.ResultsFunctional micturition cycles were observed in response to bladder filling. During each void, the bladder showed strong contractions and the external urethral sphincter (EUS) showed bursting activity. Both the frequency and amplitude of non‐voiding contractions (NVCs) in DAPM and putative micromotions (pMM) in pithed DAPM increased with bladder filling. Vasopressin (>400 pM) caused dyssynergy of the LUT resulting in retention in DAPM as it increased tonic EUS activity and basal bladder pressure in a dose‐dependent manner (basal pressure increase also noted in pithed DAPM). Both neuromuscular blockade (vecuronium) and autonomic ganglion blockade (hexamethonium), initially caused incomplete voiding, and both drugs eventually stopped voiding in DAPM. Intravesical acetic acid (0.2%) decreased the micturition interval. Recordings from the pelvic nerve in the pithed DAPM showed bladder distention‐induced activity in the non‐noxious range which was associated with pMM.ConclusionsThis study demonstrates the utility of the DAPM which allows a detailed characterization of LUT function in mice.

Influence of sildenafil on the purinergic components of nerve‐mediated and urothelial ATP release from the bladder of normal and spinal cord injured mice

“…Young mice were administered heparin (50 IU, i.p.) and anaesthetized with isoflurane (2%) until loss of paw withdrawal reflex, following the non‐recovery procedure modified from previous studies with an in situ arterially perfused rat (Sadananda, Drake, Paton, & Pickering, ) and mouse (Ito et al, ; Ito, Drake, Fry, Kanai, & Pickering, ). The brain was removed, and the spinal cord pithed with a blunt wire before arterial perfusion of the preparation.…”

Sildenafil, a phosphodiesterase type 5 inhibitor, augments sphincter bursting and bladder afferent activity to enhance storage function and voiding efficiency in mice

“…Recordings were made from the pelvic nerve in the pithed DAPM to test for an action of sildenafil on bladder primary afferent terminals . Under control conditions, intravesical saline infusion evoked an increase in pelvic afferent activity that ramped up with the increase of pressure [mean ( sem ) firing rate 0.25 (0.1) Hz at 0 mmHg and 16.8 (3.0) Hz at 15 mmHg, n = 18 preparations).…”

“…These data indicate that the effects of sildenafil on EUS‐EMG bursting arise outside the spinal cord but not within the sphincter itself. We propose that this bursting activity is important for efficient voiding in mice and rats , and that the increase of bursting will facilitate voiding. There are no previous studies measuring the effects of PDE5‐Is on the electrical activity of EUS.…”

“…For the DAPM preparation , the mouse was deeply anaesthetised with isoflurane (2–3%) and the stomach and intestine were vascularly isolated and removed through a midline laparotomy. The ureters were cut bilaterally and ligated distally to prevent bladder filling.…”

“…The present study aimed to investigate in detail the influence of the PDE5‐I sildenafil on the function and control of the mouse LUT. To help achieve this aim, without the confounding effects of anaesthesia, we employed a recently described in situ mouse model, the decerebrate arterially perfused mouse (DAPM) . This has many of the advantages of accessibility afforded by in vitro approaches but retains functional neural connectivity.…”