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Differential Rearing Alters Forced Swim Test Behavior, Fluoxetine Efficacy, and Post-Test Weight Gain in Male Rats.

Arndt DL, Peterson CJ, Cain ME - PLoS ONE (2015)

Bottom Line: Results revealed an antidepressant effect of environmental enrichment and a depressant effect of isolation.Subchronic 20 mg/kg fluoxetine also induced significant weight loss, and differential rearing appeared to moderate weight gain following FST stress.These results suggest that differential rearing has the ability to alter FST behaviors, fluoxetine efficacy, and post-stressor well-being.

View Article: PubMed Central - PubMed

Affiliation: Department of Psychological Sciences, Kansas State University, Manhattan, KS, United States of America.

ABSTRACT
Environmental factors play a key role in the etiology of depression. The rodent forced swim test (FST) is commonly used as a preclinical model of depression, with increases in escape-directed behavior reflecting antidepressant effects, and increases in immobility reflecting behavioral despair. Environmental enrichment leads to serotonergic alterations in rats, but it is unknown whether these alterations may influence the efficacy of common antidepressants. Male Sprague-Dawley rats were reared in enriched (EC), standard (SC), or isolated (IC) conditions. Following the rearing period, fluoxetine (10 or 20 mg/kg, i.p.) was administered 23.5 hrs, 5 hrs, and 1 hr before locomotor and FST measures. Following locomotor testing and FST exposure, rats were weighed to assess fluoxetine-, FST-, and environmental condition-induced moderations in weight gain. Results revealed an antidepressant effect of environmental enrichment and a depressant effect of isolation. Regardless of significant fluoxetine effects on locomotor activity, fluoxetine generally decreased swimming and increased immobility in all three environmental conditions, with IC-fluoxetine (10 mg/kg) rats and EC-fluoxetine (20 mg/kg) rats swimming less than vehicle counterparts. Subchronic 20 mg/kg fluoxetine also induced significant weight loss, and differential rearing appeared to moderate weight gain following FST stress. These results suggest that differential rearing has the ability to alter FST behaviors, fluoxetine efficacy, and post-stressor well-being. Moreover, 20 mg/kg fluoxetine, administered subchronically, may lead to atypical effects of those commonly observed in the FST, highlighting the importance and impact of both environmental condition and dosing regimen in common animal models of depression.

No MeSH data available.


Related in: MedlinePlus

Experiment III Forced Swim Test Climbing, Swimming, and Immobility.Experiment III total mean counts (±SEM) of (A) climbing, (B) swimming, and (C) immobility behavior between EC, SC, and IC rats after subchronic fluoxetine (20 mg/kg, i.p.) or vehicle administrations before the FST. (A) Asterisk (*) indicates that EC rats exhibited more climbing behavior than SC rats, irrespective of drug treatment. (B) Asterisks (*) indicate that fluoxetine rats exhibited less swimming behavior than vehicle control rats. (C) Asterisks (*) indicate that fluoxetine rats exhibited significantly more immobility than rats administered vehicle control injections (p < .05).
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pone.0131709.g007: Experiment III Forced Swim Test Climbing, Swimming, and Immobility.Experiment III total mean counts (±SEM) of (A) climbing, (B) swimming, and (C) immobility behavior between EC, SC, and IC rats after subchronic fluoxetine (20 mg/kg, i.p.) or vehicle administrations before the FST. (A) Asterisk (*) indicates that EC rats exhibited more climbing behavior than SC rats, irrespective of drug treatment. (B) Asterisks (*) indicate that fluoxetine rats exhibited less swimming behavior than vehicle control rats. (C) Asterisks (*) indicate that fluoxetine rats exhibited significantly more immobility than rats administered vehicle control injections (p < .05).

Mentions: There was no main effect of drug treatment on climbing behavior, but there was a main effect of environmental condition, F(2, 54) = 3.91, p < .05. EC rats climbed significantly more than SC rats (p < .05; αFER = .05; Fig 7A). Furthermore, there was a significant main effect of drug treatment on swimming, F(1, 54) = 14.14, p < .001. Rats that received fluoxetine exhibited less swimming than vehicle rats (p < .05; αFER = .05; Fig 7B). Lastly, drug treatment had a significant main effect on rats’ FST immobility, F(1, 54) = 9.17, p < .01; fluoxetine rats exhibited more immobility than vehicle rats (p < .05; αFER = .05; Fig 7C), once again illustrating the atypical drug effect of fluoxetine at this current dose and regimen.


Differential Rearing Alters Forced Swim Test Behavior, Fluoxetine Efficacy, and Post-Test Weight Gain in Male Rats.

Arndt DL, Peterson CJ, Cain ME - PLoS ONE (2015)

Experiment III Forced Swim Test Climbing, Swimming, and Immobility.Experiment III total mean counts (±SEM) of (A) climbing, (B) swimming, and (C) immobility behavior between EC, SC, and IC rats after subchronic fluoxetine (20 mg/kg, i.p.) or vehicle administrations before the FST. (A) Asterisk (*) indicates that EC rats exhibited more climbing behavior than SC rats, irrespective of drug treatment. (B) Asterisks (*) indicate that fluoxetine rats exhibited less swimming behavior than vehicle control rats. (C) Asterisks (*) indicate that fluoxetine rats exhibited significantly more immobility than rats administered vehicle control injections (p < .05).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4496081&req=5

pone.0131709.g007: Experiment III Forced Swim Test Climbing, Swimming, and Immobility.Experiment III total mean counts (±SEM) of (A) climbing, (B) swimming, and (C) immobility behavior between EC, SC, and IC rats after subchronic fluoxetine (20 mg/kg, i.p.) or vehicle administrations before the FST. (A) Asterisk (*) indicates that EC rats exhibited more climbing behavior than SC rats, irrespective of drug treatment. (B) Asterisks (*) indicate that fluoxetine rats exhibited less swimming behavior than vehicle control rats. (C) Asterisks (*) indicate that fluoxetine rats exhibited significantly more immobility than rats administered vehicle control injections (p < .05).
Mentions: There was no main effect of drug treatment on climbing behavior, but there was a main effect of environmental condition, F(2, 54) = 3.91, p < .05. EC rats climbed significantly more than SC rats (p < .05; αFER = .05; Fig 7A). Furthermore, there was a significant main effect of drug treatment on swimming, F(1, 54) = 14.14, p < .001. Rats that received fluoxetine exhibited less swimming than vehicle rats (p < .05; αFER = .05; Fig 7B). Lastly, drug treatment had a significant main effect on rats’ FST immobility, F(1, 54) = 9.17, p < .01; fluoxetine rats exhibited more immobility than vehicle rats (p < .05; αFER = .05; Fig 7C), once again illustrating the atypical drug effect of fluoxetine at this current dose and regimen.

Bottom Line: Results revealed an antidepressant effect of environmental enrichment and a depressant effect of isolation.Subchronic 20 mg/kg fluoxetine also induced significant weight loss, and differential rearing appeared to moderate weight gain following FST stress.These results suggest that differential rearing has the ability to alter FST behaviors, fluoxetine efficacy, and post-stressor well-being.

View Article: PubMed Central - PubMed

Affiliation: Department of Psychological Sciences, Kansas State University, Manhattan, KS, United States of America.

ABSTRACT
Environmental factors play a key role in the etiology of depression. The rodent forced swim test (FST) is commonly used as a preclinical model of depression, with increases in escape-directed behavior reflecting antidepressant effects, and increases in immobility reflecting behavioral despair. Environmental enrichment leads to serotonergic alterations in rats, but it is unknown whether these alterations may influence the efficacy of common antidepressants. Male Sprague-Dawley rats were reared in enriched (EC), standard (SC), or isolated (IC) conditions. Following the rearing period, fluoxetine (10 or 20 mg/kg, i.p.) was administered 23.5 hrs, 5 hrs, and 1 hr before locomotor and FST measures. Following locomotor testing and FST exposure, rats were weighed to assess fluoxetine-, FST-, and environmental condition-induced moderations in weight gain. Results revealed an antidepressant effect of environmental enrichment and a depressant effect of isolation. Regardless of significant fluoxetine effects on locomotor activity, fluoxetine generally decreased swimming and increased immobility in all three environmental conditions, with IC-fluoxetine (10 mg/kg) rats and EC-fluoxetine (20 mg/kg) rats swimming less than vehicle counterparts. Subchronic 20 mg/kg fluoxetine also induced significant weight loss, and differential rearing appeared to moderate weight gain following FST stress. These results suggest that differential rearing has the ability to alter FST behaviors, fluoxetine efficacy, and post-stressor well-being. Moreover, 20 mg/kg fluoxetine, administered subchronically, may lead to atypical effects of those commonly observed in the FST, highlighting the importance and impact of both environmental condition and dosing regimen in common animal models of depression.

No MeSH data available.


Related in: MedlinePlus