Hindlimb unloading elicits anhedonia and sympathovagal imbalance

Julia A Moffitt; Angela J Grippo; Alan Kim Johnson; Terry G Beltz

doi:10.1152/japplphysiol.90535.2008

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Hindlimb unloading elicits anhedonia and sympathovagal imbalance

Journal article

Open access

Peer reviewed

Hindlimb unloading elicits anhedonia and sympathovagal imbalance

Julia A Moffitt, Angela J Grippo, Alan Kim Johnson and Terry G Beltz

Journal of applied physiology (1985), Vol.105(4), pp.1049-1059

10/2008

DOI: 10.1152/japplphysiol.90535.2008

PMCID: PMC2576027

PMID: 18635876

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Abstract

The hindlimb-unloaded (HU) rat model elicits cardiovascular deconditioning and simulates the physiological adaptations to microgravity or prolonged bed rest in humans. Although psychological deficits have been documented following bed rest and spaceflight in humans, few studies have explored the psychological effects of cardiovascular deconditioning in animal models. Given the bidirectional link established between cardiac autonomic imbalance and psychological depression in both humans and in animal models, we hypothesized that hindlimb unloading would elicit an alteration in sympathovagal tone and behavioral indexes of psychological depression. Male, Sprague-Dawley rats confined to 14 days of HU displayed anhedonia (a core feature of human depression) compared with casted control (CC) animals evidenced by reduced sucrose preference (CC: 81 +/- 2.9% baseline vs. HU: 58 +/- 4.5% baseline) and reduced (rightward shift) operant responding for rewarding electrical brain stimulation (CC: 4.4 +/- 0.3 muA vs. 7.3 +/- 1.0 muA). Cardiac autonomic blockade revealed elevated sympathetic [CC: -54 +/- 14.1 change in (Delta) beats/min vs. HU: -118 +/- 7.6 Delta beats/min] and reduced parasympathetic (CC: 45 +/- 11.8 Delta beats/min vs. HU: 8 +/- 7.3 Delta beats/min) cardiac tone in HU rats. Heart rate variability was reduced (CC: 10 +/- 1.4 ms vs. HU: 7 +/- 0.7 ms), and spectral analysis of blood pressure indicated loss of total, low-, and high-frequency power, consistent with attenuated baroreflex function. These data indicate that cardiovascular deconditioning results in sympathovagal imbalance and behavioral signs consistent with psychological depression. These findings further elucidate the pathophysiological link between cardiovascular diseases and affective disorders.

Adrenergic beta-Antagonists - pharmacology

Animals

Baroreflex

Behavior, Animal - drug effects

Blood Pressure

Cardiovascular Deconditioning - drug effects

Cardiovascular System - innervation

Conditioning, Operant

Corticosterone - blood

Depression - etiology

Depression - physiopathology

Depression - psychology

Dietary Sucrose - administration & dosage

Electric Stimulation

Food Preferences

Fourier Analysis

Heart Rate

Hindlimb Suspension - adverse effects

Male

Muscarinic Antagonists - pharmacology

Rats

Rats, Sprague-Dawley

Sympathetic Nervous System - drug effects

Sympathetic Nervous System - physiopathology

Vagus Nerve - drug effects

Vagus Nerve - physiopathology

Details

Title: Subtitle: Hindlimb unloading elicits anhedonia and sympathovagal imbalance
Creators: Julia A Moffitt
Angela J Grippo
Alan Kim Johnson
Terry G Beltz
Resource Type: Journal article
Publication Details: Journal of applied physiology (1985), Vol.105(4), pp.1049-1059
DOI: 10.1152/japplphysiol.90535.2008
PMID: 18635876
PMCID: PMC2576027
NLM abbreviation: J Appl Physiol (1985)
ISSN: 8750-7587
eISSN: 1522-1601
Grant note: HL 57472 / NHLBI NIH HHS MH 65839 / NIMH NIH HHS HL 14388 / NHLBI NIH HHS DK 066086 / NIDDK NIH HHS
Language: English
Date published: 10/2008
Academic Unit: Psychological and Brain Sciences; Neuroscience and Pharmacology; Health, Sport, and Human Physiology
Record Identifier: 9984213279102771

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