[Autonomic nervous system estimation by heart rate variability analysis in experimental short and long-lasting bladder outlet obstruction model]

Abstract

Introduction: Benign prostatic hyperplasia; BPH is associated with the symptoms of the bladder overactivity. This disease can be comparatively easly induced using an animal model of the partial bladder outlet obstruction; PBOO. The pathophysiological description of BPH is still incomplete, thus autonomic nervous system activity assessement in the course of PBOO seems to be important.

Material and methods: The experiment was carried out on 30 Wistar rats. 10 animals "sham" operated served as control group (group 1). Another 20 rats underwent the PBOO surgery. In all studied animals in urethane anaesthesia short-term (20 minutes lasting) heart rate variability (HRV) recordings were taken with the subse quent time-and spectral HRV analysis. In control rats, the HRV study was done after 7 days of sham operation while the PBOO animals were divided into two subgroups: with short lasting PBOO (group 2; the HRV records were collected on the 14th the day since the surgery) and with long-lasting PBOO (group 3; HRV records on the 29th day after surgery). After HRV collection, all studied animals were given a lethal pentobarbital dose and urinary bladders were removed for histopathological assessement.

Results: Bladders collected from PBOO rats were characterised by signs of congestion and edema with features of the excessve bladder wall muscularisation. The majority of the time-domain HRV analyzed parameters did not significantly differ in all studied groups. The total HRV spectrum power(TP), as well as the power of the low frequency component (LF) and high frequency one (HF) were markedly higher in the control group. In PBOO animals, the trend of the progressive power decrease of main HRV spectrum components was observed. The significant changes relating to the standardized HRV parameters were pronounced. In control rats, the nLF value was smaller while nHF - higher when compared to the group 2. Just the opposite, when combine the control and 3 group it was showed, that the value of nLF was higher and nHF - smaller in control animals.

Conclusions: Our results suggest, that the partial bladder outlet obstruction causes both the bladder remodelling and the functional changes of the autonomic nervous system which become more stressed with the BOO duration. 14-days lasting PBOO model caused decrease of the global autonomic tension, but with the maintaining of the mutual relations between the main ANS branches: sympathetic part and parasympathetic one. The monthly PBOO period caused the more marked autonomic dysfunction manifesting by considerable lowering of the total autono mic tension and the shift of autonomic balance towards to o parasympathetic predominance.