Corticosterone response to the plus-maze: High correlation with risk assessment in rats and mice
ABSTRACT Exposure to the elevated plus-maze induces behavioural and physiological effects in rodents consistent with fear/anxiety. Maze-naive animals display high levels of risk assessment towards the open arms, and explore these areas less extensively than other parts of the maze while, immediately following the test, pain latencies, skin conductance levels, and plasma corticosterone titres (CORT) are significantly elevated. Although previous research has suggested a link between the plasma CORT response and open-arm exploration, significant elevations in CORT have also been found with restricted exposure to the closed arms. The present study employed ethological measures in an attempt to further characterise the relationship between behavioural and CORT responses to this widely used animal model of anxiety. Our results confirm that, relative to home-cage controls, 5-min exposure to the plus-maze significantly increases plasma CORT levels in test-naive male Wistar rats and male Swiss-Webster mice. Furthermore, in both species, the CORT response was found to be highly correlated with measures of risk assessment (mice: rs = +0.87; rats: rs = +0.58), but not with measures of open-arm activity (entries, time), general locomotor activity, rearing, or head dipping. Findings are discussed in relation to the functional significance of risk assessment in potentially dangerous situations and the potential involvement of glucocorticoids in this process. All rights reserved.
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- "(Rodgers et al., 1999 "
ABSTRACT: Abstract Early separation from a family is stressful for young mammals, but might be more stressful for group-living than solitary species. Using juvenile males of three African striped mice Rhabdomys taxa that are either group (R. pumilio) or solitary (R. dilectus dilectus and R. d. chakae) living, we predicted greater separation anxiety in R. pumilio than R. dilectus because group-living could reduce anxiety in R. pumilio. Three brothers from each of 10 litters per taxon were randomly assigned soon after natural weaning (25 days) to one of three treatments for 10 days: 1) remained with the family (philopatric); 2) separated from the family by a wire mesh barrier (separated); and 3) isolated from the family (isolated). Males were individually tested in a four-arm maze to assess their anxiety responses and sampled for corticosterone concentrations 20 mins and 10 days later. Compared to R. dilectus males, R. pumilio males showed a greater treatment response to separation: philopatric males used the light arms of the maze less and had higher corticosterone concentrations compared to isolated males, which spent the most time in the light arms and had the lowest corticosterone concentrations overall; separated males showed an intermediate behavioural response, but had similar corticosterone concentrations to philopatric males. Thus, separation from a family group is more stressful in group-living Rhabdomys and this stress response dissipates with time. Philopatry and group-living may be more important for young R. pumilio, whereas dispersal at weaning is an important life history event for solitary R. dilectus.Stress (Amsterdam, Netherlands) 04/2014; DOI:10.3109/10253890.2014.910762 · 3.46 Impact Factor
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- "Coincident with the anxiogenic/ anxiolytic roles of CRH and TRH, opposite changes were detected in the expression of TRH, and the elements involved in its transmission, as amygdalar TRHergic neurons appeared inhibited after OFT-L while activated after OFT-D. The conventional test duration of 5 min was chosen for EPM or OFT when animals display a more active behavior and produced a stress response since corticosterone serum concentrations increased at 15 and 30 min after test ended (Carobrez and Bertoglio, 2005; Hall et al., 2000; Rodgers et al., 1999 "
ABSTRACT: Central administration of thyrotropin releasing hormone (TRH) reduces anxiety; amygdalar TRH expression is inversely proportional to the anxious behavior displayed in the elevated plus maze performed during the dark phase (EPM-D). To better understand the role of TRH in amygdala function, we evaluated the expression of TRH and the elements involved in its transmission in various stressful paradigms and how they associated with behavior. Wistar male rats were exposed to restraint (RES), EPM, or the open field test (OFT) and sacrificed 0-60 min afterwards; OFT, RES and EPM were performed during the light (L), and OFT during the dark phase. Restraint increased amygdalar levels of proCRH mRNA, without change in proTRH. All paradigms augmented corticosterone release, highest after OFT-L that also enhanced proCRH mRNA levels and decreased those of proTRH. OFT-D activated the TRH system. Levels of anxiety or locomotion were similar in animals tested in light or dark phases but their association with biochemical parameters differed. ProTRH expression and TRH release correlated positively with decreased anxiety in EPM-L and in OFT-D. No association with anxiety was detected in OFT-L where proCRH and proTRH expression correlated with locomotion supporting their involvement in arousal. The responses of TRH amygdalar systems appeared modulated by the extent of the stress response and by the circadian conditions. Increased proTRH expression of animals exposed to OFT-D was specifically observed in the cortical nucleus of the amygdala, area involved in processing fear stimuli; these TRH neurons may thus be part of a circuit with anxiolytic properties.Brain research 03/2012; 1452:73-84. DOI:10.1016/j.brainres.2012.02.071 · 2.83 Impact Factor
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- "In the field studies, vigilance is commonly defined in terms of searching/scanning activity and is typically measured as the tendency of an animal to scan the environment (i.e., to look around), as opposed to eating, grooming, sleeping, or other nondefensive behaviors (Lima 1987). In laboratory rodent studies, the most commonly used measures of risk assessment behaviors include stretched attend posture (SAP), " flat-back " approach, and protected head-dips/head-outs (Blanchard et al. 1990; Choleris et al. 2001; Cole and Rodgers 1994; Griebel et al. 1997; Rodgers et al. 1999; Roy and Chapillon 2004). The vigilant scanning has also been reported by a number of rodent studies, mostly as a part of " head-out " behavior (Blanchard and Blanchard Choy and Yu contributed equally to this work. "
ABSTRACT: Vigilant scanning of the environment is a major risk assessment activity in many species. However, due to difficulties in its manual scoring, scanning has rarely been quantified in laboratory rodent studies. We developed a novel method for automated measurement of vigilant scanning in mice, based on simultaneous tracking of an animal's nose- and center-points. The studied scanning parameters included the frequency and duration of scans and scanning (nose-point) speed. The sensitivity of these parameters to anxiolytic diazepam (1-2 mg/kg) and anxiogenic FG-7142 (5 mg/kg) was evaluated upon exposure to the context (conditioning chamber) before and 24 h after footshock. Scanning behavior was observed in all C57BL/6, 129xC57BL/6, and DBA/2 mice, as recurrent stationary episodes accompanied by observatory head movements. These episodes respectively comprised 28 ± 1%, 29 ± 1%, and 24 ± 2% of preexposure time. Diazepam dose-dependently decreased the scanning frequency and duration, without affecting the scanning speed. Fear conditioning increased freezing and inhibited other behaviors upon reexposure, with scanning being only marginally affected and still comprising 17 ± 2%, 16 ± 2%, and 19 ± 1% of reexposure time, respectively. Consequently, scanning accounted for most (DBA/2) or virtually all (C57BL/6 and 129xC57BL/6) gross motor activities upon reexposure. FG-7142 mirrored the effects of conditioning, inducing behavioral inhibition with scanning being least affected. Two-point tracking is effective for studying vigilant scanning in mice. Using this approach, we show that scanning is a key risk assessment activity in both unconditioned and conditioned mice; scanning is resistant to threat-induced behavioral inhibition and is highly sensitive to anxiolytic treatment.Psychopharmacology 12/2011; 221(4):649-57. DOI:10.1007/s00213-011-2609-5 · 3.99 Impact Factor