Subtle Cardiovascular Dysfunction in the Unilateral 6-Hydroxydopamine-Lesioned Rat

Q: What are the key findings of this study?

Unilateral 6-OHDA medial forebrain bundle lesioning in rats significantly reduced the diurnal rhythm of heart rate, causing a greater nocturnal heart rate decrease of 38 bpm vs 17 bpm in controls (P<0.05).

Q: What is the clinical evidence from this study?

Population: Parkinson's disease (unilateral 6-OHDA rat model) (n=40). Intervention: Unilateral 6-hydroxydopamine (6-OHDA) medial forebrain bundle lesion vs. Sham surgery (vehicle solution) or unoperated controls. Primary outcome: Nocturnal heart rate decrease from baseline (diurnal rhythm of heart rate) (p=<0.05).

Q: What does this research mean for the field?

Unilateral 6-hydroxydopamine medial forebrain bundle lesioning in rats induces subtle cardiovascular autonomic dysfunction characterized by a significantly reduced diurnal rhythm of heart rate and exaggerated nocturnal heart rate decrease. Novelty: ClaimNovelty.NOVEL_FINDING. Consensus alignment: ConsensusAlignment.NEUTRAL.

Q: What question did this study set out to answer?

To evaluate whether the unilateral 6-hydroxydopamine (6-OHDA) rat model of Parkinson's disease develops autonomic cardiovascular deficits.

Katy Slack; R. Billing; Slade T. Matthews; Haydn N. Allbutt; Rosemarie Einstein; J. M. Henderson

doi:10.4061/2010/427810

January 1, 2010Parkinson s DiseaseOpen Access

Subtle Cardiovascular Dysfunction in the Unilateral 6-Hydroxydopamine-Lesioned Rat

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Key result

Unilateral 6-OHDA brain lesioning drives a ~21 bpm greater nocturnal heart rate drop in rats.

P<0.05
n=40

Why the study?

Whether the unilateral 6-hydroxydopamine (6-OHDA) rat model of Parkinson's disease produces autonomic deficits was evaluated.

Key Points

To evaluate whether the unilateral 6-hydroxydopamine (6-OHDA) rat model of Parkinson's disease develops autonomic cardiovascular deficits.
Rats received implanted radiofrequency telemetry devices to track heart rate variability, diurnal heart rate rhythms, core body temperature, and locomotor activity.
Animals then underwent unilateral 6-OHDA lesioning (n = 8) or sham surgery (n = 6) targeting the medial forebrain bundle.
Behavioral testing (postural biases, apomorphine rotation, and disengage sensorimotor test) was conducted alongside telemetric monitoring from day 4 to days 12–14 post-surgery.
6-OHDA lesioned rats showed prominent behavioral deficits, including head and body axis biases, defective sensorimotor responses in the disengage test (P < .0001), and apomorphine rotation (all P < .05 versus controls).
The diurnal rhythm of heart rate was significantly lower in 6-OHDA lesioned rats (n = 8) compared with controls (n = 6; P < .05).
While daytime heart rate dropped by 19 b.p.m. in lesioned rats and 21 b.p.m. in sham controls, lesioned rats experienced a greater nocturnal heart rate decrease from baseline (by 38 b.p.m. versus 17 b.p.m. in controls; P < .05), with no differences in locomotor activity or core body temperature.

PICO

P

Population

40 female Sprague-Dawley rats (aged 10-12 weeks, 30 analyzed after exclusions for surgical complications or incomplete lesions) undergoing unilateral 6-OHDA lesioning or sham surgery, followed for 2 weeks post-lesion.

I

Intervention / Comparator

Unilateral 6-hydroxydopamine (6-OHDA) medial forebrain bundle lesion vs Sham surgery (vehicle solution) or unoperated controls (4 μg/μl in 0.1% ascorbate saline delivered at 1 μl/min for 4 minutes)

O

Primary Outcome

Nocturnal heart rate decrease from baseline (diurnal rhythm of heart rate), p=<0.05

Main Result

Absolute Event Rate: 38% vs 17%

p-value: p=<0.05

Limitations

Preclinical animal model (rats) rather than human subjects
Small sample size for telemetric and chronobiological analysis (n=14 for telemetry, n=10 for HRV/circadian analysis due to technical issues)
Ten out of 40 animals excluded due to surgical complications (n=6) or inadequate lesioning (n=4)
Lack of significant periodicity in approximately 40% of the 24-hour recordings limited chronobiological analysis
Generalized postoperative and anesthetic effects of surgery itself altered heart rate and HRV in both sham and lesioned groups
Short post-lesion follow-up duration of 2 weeks

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Implication

Findings remain preclinical; leaves open whether unilateral 6-OHDA lesions model human PD autonomic HR changes.

Abstract

The present study evaluated whether the unilateral 6-hydroxydopamine (6-OHDA) model of Parkinson's disease produces autonomic deficits. Autonomic parameters were assessed by implanting a small radiofrequency telemetry device which measured heart rate variability (HRV), diurnal rhythms of heart rate (HR), core body temperature (cBT) and locomotor activity (LA). Rats then received 6-OHDA lesion or sham surgery. 6-OHDA lesioned rats exhibited head and body axis biases, defective sensorimotor function ("disengage" test), and prominent apomorphine rotation (all P < .05 versus controls). Diurnal rhythm of HR was lower for 6-OHDA lesioned rats (n = 8) versus controls (n = 6; P < .05). Whilst HR decreased similarly in both groups during the day, there was a greater decrease in HR for the 6-OHDA lesioned rats at night (by 38 b.p.m. relative to 17 b.p.m. for controls). LA and cBT did not differ between surgery groups. This study indicates the unilateral 6-OHDA model of PD shows subtle signs of cardiovascular autonomic dysfunction.

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Cite This Study

Slack et al. (2010) studied Parkinson's disease (unilateral 6-OHDA rat model) (n=40). Unilateral 6-hydroxydopamine (6-OHDA) medial forebrain bundle lesion vs. Sham surgery (vehicle solution) or unoperated controls was evaluated on Nocturnal heart rate decrease from baseline (diurnal rhythm of heart rate) (p=<0.05). Unilateral 6-OHDA medial forebrain bundle lesioning in rats significantly reduced the diurnal rhythm of heart rate, causing a greater nocturnal heart rate decrease of 38 bpm vs 17 bpm in controls (P<0.05).

synapsesocial.com/papers/6adf2611a856943a93c14f25 https://doi.org/10.4061/2010/427810

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Subtle Cardiovascular Dysfunction in the Unilateral 6-Hydroxydopamine-Lesioned Rat

Key Points

PICO

Main Result

Limitations

Ask about this paper

Implication

Abstract

Discussion

Cite This Study

Subtle Cardiovascular Dysfunction in the Unilateral 6-Hydroxydopamine-Lesioned Rat

Key Points

PICO

Main Result

Limitations

Ask about this paper

Implication

Abstract

Discussion

Cite This Study

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