Exposure to Repeated Cold Stress Influences Sympathetic and Cardiovascular Responses to Muscle Stretch in Decerebrated Rats, 2022, Hori et al

Abstract

Chronic stress is known to cause adverse physical and mental effects such as pain, chronic fatigue, and depression, and it is strongly related to many diseases and syndromes (e.g., fibromyalgia, chronic fatigue syndrome, and post-traumatic stress disorder). Evidence suggests that exercise and physical activity in leisure time are effective in improving stress-induced symptoms. Repeated cold stress (RCS), in which an animal is repeatedly exposed to alternating room and low temperatures, is one of the chronic stress models that induces chronic pain and depression. Mechanical hyperalgesia through thin muscle afferent fibers has also been reported to occur from RCS exposure. Since the muscle afferents have a dual modulatory function in nociception and cardiovascular reflex, we hypothesized that RCS augments the mechanical component of the exercise pressor reflex (the skeletal muscle mechanoreflex), i.e., skeletal muscle afferents-mediated increases sympathetic nerve activity (SNA) and arterial blood pressure (AP).

[Purpose]
The purpose of this study was to clarify the impacts of RCS on sympathetic and cardiovascular responses to stimulation of the skeletal muscle mechanoreflex in decerebrated rats.

[Methods]
Male Sprague-Dawley rats (body weight: 410 ± 15 g, age: 12 weeks) were exposed to RCS using a homemade automated RCS device. The rats were alternately moved to room temperature (22°C) and cold temperature (4°C) compartments at 30-min intervals for 5 days. To assess the skeletal muscle mechanoreflex function, we measured mean AP (MAP), heart rate (HR), and renal SNA (RSNA) responses to 30-s static passive stretching of the hindlimb muscles by in vivo recording from unanesthetized decerebrated rats. Stretching was performed by tracing the maximum tension curve obtained from 30-s electrical stimulation. Changes (Δ) from baseline to peak values of the measured parameters between control and RCS rats were compared.

[Results]
Peak tension during the Achilles tendon stretch from baseline was not significantly different between groups (control: Δ929 ± 63 g [n = 6] vs RCS: Δ765 ± 66 g [n = 4], p = 0.17). Importantly, the peak RSNA response in RCS rats (Δ236.3% and Δ242.7%, n = 2) tended to be greater than that in control rats (Δ37.1% and Δ23.9%, n = 2). Moreover, RCS had a significantly (p < 0.05) greater HR response (RCS: Δ3.7 ± 1.0 bpm [n = 4] vs control: Δ0.6 ± 0.5 bpm [n = 6]), and MAP response tended (P = 0.07) to be higher in the RCS group (Δ23 ± 6 mmHg, n = 4) than in the control group (Δ8 ± 4 mmHg, n = 6).

[Conclusions]
Our preliminary data demonstrate that RCS augments the skeletal muscle mechanoreflex. These results suggest that chronic stress can potentially cause exaggerated cardiovascular responses during physical activity.

This is the full abstract presented at the Experimental Biology meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract.

https://faseb.onlinelibrary.wiley.com/doi/10.1096/fasebj.2022.36.S1.R2475

 

Not true, in my experience. Chronic pain causes fatigue, depression and stress.

I looked up the meaning of "decerebrated" (although I had correctly guessed it anyway):

I wonder why anyone would do this experiment, and what relevance it has to humans.

 

Stress can mean literally anything, including going back and forth between hot and cold.

How is that any more scientific than attributing the same effects to evil spirits? If it can literally be anything, it's nothing.

Stress. Life events. Things. Stuff. Can this possibly be any more vague?

 

Surely rats, ones whose brains haven't been mucked about with, endure this type of stress routinely, every day, when day time temperatures drop to night time temperatures.

I would assume that, as rats exist, or so I'm told, that evolution must have provided them with a method of dealing, with something that literally happens at least once a day to them.

But, it appears some people really dislike rats

 

I feel sick. The cruelty.

 

Sometimes psychology is evil.

 

I wish I hadn't logged on today