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Time-related immunomodulation by stressors and corticosterone transdermal application in toads.

ABSTRACT: Immune responses have been mostly studied at a specific time in anuran species. However, time-changes related to immunomodulation associated with glucocorticoid (GC) alterations following stressors and GC treatment are complex. The present study describes time-related changes in immune response and corticosterone (CORT) plasma levels following restraint challenge, short, mid and long-term captivity, and CORT exogenous administration by transdermal application (TA) in Rhinella ornata toads. We observed increased neutrophil: lymphocyte ratios after restraint challenge and CORT TA, without changes following short and mid-term captivity. Plasma bacterial killing ability was sustained in all treatments, except long-term captivity, with decreased values after 90 days under such conditions. Phagocytic activity of peritoneal cells increased after mid-term captivity, and the phytohemagglutinin swelling response was impaired in those animals treated with CORT TA for 20 consecutive days. Plasma CORT levels increased or were sustained after restraint challenge (depending on initial values), decreased following mid and long-term captivity (for those animals showing high CORT in the field) and increased after 20 days of CORT TA. By performing assessments of time-changes in immune processes and CORT plasma levels in R. ornata, we demonstrate immuno-enhancing effects following restraint, short and mid-term stressors, while long-term stressors and CORT TA promoted immunosuppression in these toads.

SUBMITTER: Titon SCM

PROVIDER: S-EPMC6754171 | biostudies-literature | 2019

REPOSITORIES: biostudies-literature

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Time-related immunomodulation by stressors and corticosterone transdermal application in toads.

Titon Stefanny Christie Monteiro SCM Titon Braz B Barsotti Adriana Maria Giorgi AMG Gomes Fernando Ribeiro FR Assis Vania Regina VR

PloS one 20190920 9

Immune responses have been mostly studied at a specific time in anuran species. However, time-changes related to immunomodulation associated with glucocorticoid (GC) alterations following stressors and GC treatment are complex. The present study describes time-related changes in immune response and corticosterone (CORT) plasma levels following restraint challenge, short, mid and long-term captivity, and CORT exogenous administration by transdermal application (TA) in Rhinella ornata toads. We ob ...[more]

PMID: 31539413

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Project description:RATIONALE:Effort-related choice tasks are used to study aspects of motivation in both rodents and humans (Der-Avakian and Pizzagalli Biol Psychiatry 83(11):932-939, 2018). Various dopaminergic manipulations and antidepressant treatments can shift responding to these tasks (Randall et al. Int J Neuropsychopharmacol 18(2), 2014; Yohn et al. Psychopharmacology 232(7):1313-1323, 2015). However, while chronic stress can precipitate mood disorders in humans, there is relatively little known about whether chronic stress elicits maladaptive behaviors in rodent effort-related choice tasks. OBJECTIVES:Chronic corticosterone (CORT) elicits an increase in negative maladaptive behaviors in male mice (David et al. Neuron 62(4):479-493, 2009; Gourley et al. Biol Psychiatry 64(10):884-890, 2008; Olausson et al. Psychopharmacology 225(3):569-577, 2013). We hypothesized that chronic CORT administration to male mice would reduce motivation for a higher effort, higher reward option, and shift responding to a less effortful, but a lesser reward. METHODS:Adult male C57BL/6J mice were administered either vehicle (n = 10) or CORT (n = 10) (~ 9.5 mg/kg/day) in their drinking water for 4 weeks, and then throughout all behavioral experiments (15 weeks total), and were tested in a Y-Maze barrier task and a fixed ratio concurrent (FR/chow) choice task. RESULTS:Chronic CORT reduced Y-maze HR arm choice when more effort was required to obtain the 4 food pellets (15-cm barrier in the high-reward (HR) arm, p < 0.001; 20-cm barrier in HR arm, p < 0.001) and shifted choice to the low reward (LR) arm where only 2 pellets were available. Chronic CORT also reduced lever pressing for food pellets in FR30/chow sessions of the concurrent choice task (p = 0.009), without impacting lab chow consumed. CONCLUSIONS:Chronic stress induces maladaptive shifts in effort-related choice behavior in the Y-maze barrier task in male mice. Furthermore, males subjected to chronic CORT administration show reduced lever pressing in FR30/chow sessions where lab chow is concurrently available. These data demonstrate that chronic corticosterone reduces motivation to work for and obtain a highly rewarding reinforcer when a lesser reinforcer is concurrently available.

Dataset Information

Time-related immunomodulation by stressors and corticosterone transdermal application in toads.

Publications

Time-related immunomodulation by stressors and corticosterone transdermal application in toads.

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