Altered detrusor contractility in MPTP-treated common marmosets with bladder hyperreflexia

Abstract

Bladder hyperreflexia is a common non-motor feature of Parkinson's disease. We now report on the contractility of the isolated primate detrusor strips devoid of nerve input and show that following MPTP, the amplitude and frequency of spontaneous contraction was increased. These responses were unaffected by dopamine D1 and D2 receptor agonists A77636 and ropinirole respectively. Contractions by exogenous carbachol, histamine or ATP were similar and no differences in the magnitude of noradrenaline-induced relaxation were seen in detrusor strip obtained from normal and MPTP-treated common marmosets (Callithrix jacchus). However, the neurogenic contractions following electrical field stimulation of the intrinsic nerves (EFS) were markedly greater in strips obtained from MPTP treated animals. EFS evoked non-cholinergic contractions following atropine were also greater but the contribution of the cholinergic innervation as a proportion of the overall contraction was smaller in the detrusor strips of MPTP treated animals, suggesting a preferential enhancement of the non-cholinergic transmission. Although dopaminergic mechanism has been proposed to underlie bladder hyperreflexia in MPTP-treated animals with intact bladder, the present data indicates that the increased neurogenically mediated contractions where no extrinsic innervation exists might be due to long-term adaptive changes locally as a result of the loss of the nigrostriatal output.

Fig 1

In situ localisation of normal (a) and MPTP-treated bladder in the hypogastric region of the common marmoset. Invariably, the bladder of the MPTP-treated common marmosets were larger in size.

Fig 2. Tyrosine hydroxylase immunoreactivity in the substantia nigra (SN) of normal (a) and MPTP-treated common marmosets.

TH-immunoreactive neurones in normal, drug naive (a) and MPTP-treated (b) substantia nigra were significantly reduced at the level of 3^rd cranial nerve following MPTP treatment. Each data point represents mean ± sem (n = 7) ***P<0.001(c). The scale bar represents 200 μm.

Fig 3

Contractile response of the isolated detrusor strips from normal (a) and MPTP-treated common marmoset (b) to ATP. Traces showing cumulative application of ATP produced similar contractile responses in both tissues, which were equally prone to desensitisation to subsequent ATP application. In panels c-e, the time course of the contractions to the first (c), second (d) and the third (e) application of ATP suggests that there were no significant differences between responses of the tissues obtained from normal (red data points) and MPTP-treated animals. Each data point represents mean ± sem (n = 4).

Fig 4

Concentration-response effects of carbachol (a) and histamine (b) on detrusor strips from drug-naïve control and MPTP-treated animals. Each data point represents mean ± sem (carbachol, n = 28; histamine n = 7).

Fig 5

Spontaneous contractile responses (a) in isolated drug-naïve (red trace) and MPTP-treated common marmoset detrusor strips (blue trace). The strips from MPTP-treated animals exhibited greater frequency (b) and amplitude (c) of contraction compared to detrusor strips isolated from drug-naïve control animals or in the presence of selective D1 and D2 receptor agonists A77636 and ropinirole respectively. Each data point represents mean ± sem (n = 4–7) *p<0.05; **P<0.001; ns, not significant.

Fig 6. Frequency dependent increase in contractile response of isolated detrusor strips in response to EFS trains of 20 pulses at frequencies ranging from 0.25 to 40 Hz.

Representative traces showing contractile responses of detrusor strips from drug-naïve (a) and MPTP-treated common marmoset (b) in response to trains of 20 pulses at frequencies ranging from 0.25 to 40 Hz. EFS-evoked contractile responses of MPTP-treated detrusor was larger at all stimulation frequencies above 1.0 Hz (c). Time course of EFS-evoked contractile responses of detrusor strips from normal and MPTP-treated common marmosets at 4 Hz (d) and 40 Hz (e) shows a biphasic contractile profile with two distinct 1^st and 2^nd peaks. The vertical lines marked 1^st and 2^nd indicate peak phasic and tonic responses respectively. Each data point represents mean ± sem (n = 19–22) * P<0.05, **P<0.005.

Fig 7. Frequency dependent increase in contractile response of isolated detrusor strips in response to trains of 20 pulses at frequencies ranging from 0.25 to 40 Hz in the absence or in the presence of 1 μM atropine in normal and equivalent tissues from MPTP animals respectively.

In detrusor strips from drug naïve animals, atropine significantly inhibited peak contractile responses at frequencies above 20 Hz (a). In strips from MPTP-treated animals (b), atropine did not significantly decrease peak contractions. Time course of EFS-evoked contractile responses of detrusor strips from normal detrusor strips at 4 Hz (c) and 40 Hz (d) shows a biphasic contractile profile. In this tissue both phases of contraction were reduced by atropine while in MPTP tissues, atropine inhibited the second phase to a greater extent at the 4 Hz (e) and 40 Hz (f). Each data point represents mean ± sem (n = 5) * P<0.05.

Fig 8

Frequency dependent increase in contractile response of the isolated detrusor strips in response to trains of 20 pulses at frequencies ranging from 0.25 to 40 Hz in the in the presence of 1 μM atropine in normal and the equivalent tissues obtained from MPTP-treated animals (a). Expanded time-course data shows that the first phase of contraction was markedly larger in MPTP strips compared to detrusor strips from normal drug naïve animals at 4 Hz (b) and 40 Hz (c). Each data point represents mean ± sem (n = 4–5) * P<0.05, **P<0.005.

Fig 9. Frequency dependent increase in the atropine-resistant contractile response of the isolated detrusor strips in response to trains of 20 pulses at frequencies ranging from 0.25 to 40 Hz in the absence or following ATP-desensitisation (x3, 1mM ATP).

In the detrusor strips from drug naïve animals (a, c, d), ATP-desensitisation non-significantly inhibited peak contractile responses throughout the range of frequencies used (a) whereas in the strips obtained from MPTP-treated animals (b), the contractions were significantly decreased at frequencies beyond 4Hz. Time course of EFS-evoked contractile responses of detrusor strips from normal detrusor strips at 4 Hz (c) and 40 Hz (d) shows a greater inhibition of the primary peak at 4 and 40 Hz in the tissues obtained from MPTP-treated animals (e and f) compared to tissues from normal animals (c and d). Each data point represents mean ± sem (n = 4) * P<0.05, **P<0.005, ***P<0.001.