Quantitative analysis of c-Fos immunoreactivity in HAB, NAB and LAB mice under basal conditions and after OA exposure.

<p>Depicted are those areas (septal, hippocampal, amygdalar and hind brain areas) for which the Fischer LSD <i>post hoc</i> test revealed statistically significant differences in OA-stress-induced c-Fos response in HAB, NAB and LAB mice. Each column indicates the mean±SEM number of c-Fos positive cells in a tissue area of 0.01mm² (total c-Fos expression was quantified in the dentate gyrus). Basal groups: n = 5, OA-exposure: HAB: n = 9, NAB: n = 8, LAB: n = 8; *p<0.05, **p<0.01 vs HAB OA-group; # p<0.05, ## p<0.01 vs corresponding basal group; + p<0.05, ++ p<0.01 vs LAB OA-group;</p

Quantitative analysis of c-Fos immunoreactivity in HAB, NAB and LAB mice under basal conditions and after OA exposure.

<p>Depicted are those areas (cortical, accumbal and hypothalamic areas), for which the Fischer LSD <i>post hoc</i> test revealed statistically significant differences in OA-stress-induced c-Fos response in HAB, NAB and LAB mice. Each column indicates the mean±SEM number of c-Fos positive cells in a tissue area of 0.01mm² (total c-Fos expression was quantified in the dentate gyrus). Basal groups: n = 5, OA-exposure: HAB: n = 9, NAB: n = 8, LAB: n = 8; *p<0.05, **p<0.01 vs HAB OA-group; # p<0.05, ## p<0.01 vs corresponding basal group; + p<0.05, ++ p<0.01 vs LAB OA-group;</p

Schematic diagram showing the 59 areas in which c-Fos expression was quantified.

<p>Levels are based on the atlas of Franklin and Paxinos (1997). Squares indicate the placement of grids for counting of c-Fos positive cells. Asterisks indicate the regions in which HAB mice showed changes in OA-induced c-Fos expression as compared to LABs. AcB, nucleus (n.) accumbens; AcBc, n. accumbens core; AcBsh, n. accumbens shell; ACo, anterior cortical n. of the amygdala; AD, anterodorsal thalamic n.; AH, anterior hypothalamic area; Arc, arcuate hypothalamic nucleus; BlA, basolateral n. of the amygdala; BNST, bed n. of the stria terminalis; CA1, CA1 field of the hippocampus; CA3, CA3 field of the hippocampus; CeA, central n. of the amygdala; Cg 1, cingulate ctx (area1); Cg 2, cingulate ctx (area2); Cl, Claustrum; CPu, caudate putamen; cPAGdl, caudal dorsolateral periaqueductal gray; cPAGdm, caudal dorsomedial periaqueductal gray; cPAGl, caudal lateral periaqueductal gray; cPAGvl, caudal ventrolateral periaqueductal gray; DEn, Endopiriform ctx, dorsal; DG, dentate gyrus; DMH, dorsomedial hypothalamic n.; DP, dorsal peduncular nucleus; DR, dorsal raphe n.; GI, granular insular ctx; IL, infralimbic ctx; LA, lateral n. of the amygdala; LC, locus coeruleus; LGP, lateral globus pallidus; LH, lateral hypothalamic area; LHb, lateral habenular n.; LPB, lateral parabrachial n.; LSD, lateral septal n. (dorsal); LSI, lateral septal n. (intermediate); LSV, lateral septal n. (ventral); M1, primary motor ctx; M2, secondary motor ctx; MeA, medial amygdala; MGP, medial globus pallidus; MO, medial orbital cortex; MPA, medial preoptic area; MPO, medial preoptic n.; MPB, medial parabrachial n.; PE, periventricular n; Pir, piriform ctx; PLCo, posterolateral cortical n. of the amygdala; PrL, prelimbic ctx; PV, paraventricular thalamic n.; PVA, paraventricular thalamic n. (anterior); PVN, paraventricular hypothalamic n.; rPAGdl, rostral dorsolateral periaqueductal gray; rPAGdm, rostral dorsomedial periaqueductal gray; rPAGl, rostral lateral periaqueductal gray; RSA, retrosplenial agranular ctx; RSG, retrosplenial granular ctx; S1J, primary somatosensory cortex, jaw region; VMH, ventromedial hypothalamic n.</p

Overview of c-Fos expression following open arm (OA) exposure in HAB, NAB and LAB mice.

<p>Values are numbers of c-Fos positive cells/0.01 mm². (total number of c-Fos positive cells was quantified in the CA1 and CA3 region and the dentate gyrus of the hippocampus). 2-way ANOVA analysis results for <i>line x stress</i> interaction are given in the right column (brain areas showing significant interaction are shown in bold). 2-way ANOVA analysis results for the factor <i>stress</i> are indicated by # P<0.05, ## P<0.01 basal versus OA stress groups; basal groups: n = 5, OA-groups: n = 8–9;</p

Behavioral parameters of HAB, NAB and LAB mice measured in the 5-min exposure to the OA.

<p>(a) Time spent in distal zone, entries into distal zone, total distance traveled. (b) Head-dip behavior. Values are expressed as mean±SEM. HAB: n = 9, NAB: n = 8, LAB: n = 8; * p<0.05, ** p<0.01.</p

Short- and long-term recall of cued conditioned fear in HAB and NAB mice.

<p>CS only was presented to separate HAB and NAB groups 1 h, 6 h (short-term) or 24 h (long-term) after cued fear conditioning. Irrespective of consolidation period, HAB mice showed pronounced freezing during the fear expression test, but not NAB mice. Data are presented as means ± SEM. <i>n</i> = 6–8 per experimental group. ***<i>p</i><0.001 HAB vs. NAB.</p

Correlation analysis of <i>distal arm entries</i> and <i>c-Fos responses</i> in brain areas where HAB, NAB and LAB mice showed significant differences in OA stress-induced c-Fos response.

<p>R and P values revealed by the Spearman test are presented for each brain region.</p

Contextual conditioned fear in HAB and NAB mice.

<p>Although freezing behaviour (assessed during each 2-min period post US presentation) increased in HAB and NAB animals in response to 5 US presentations to the same extent (A), indicating comparable fear conditioning of both lines, HAB mice displayed significantly higher fear responses than NAB mice when exposed to the conditioning context for 3 min 24 h later (B). Data are presented as means ± SEM. <i>n</i> = 9 per line. **<i>p</i><0.01 HAB vs. NAB, ^§§<i>p</i><0.01 fear expression vs. last US presentation.</p

Pharmacological modulation of learned cued fear in HAB mice.

<p>An acute application of either the α_2,3,5-subunit selective benzodiazepine partial agonist L-838,417 (1 mg/kg; A), corticosterone (CORT; 10 mg/kg; B) or the selective NK1 receptor antagonist L-822,429 (30 mg/kg; C) 30 min prior to testing reduced fear expression as indicated by the percentage of freezing displayed by HAB mice during fear expression. Chronic treatment with L-822,429 (30 mg/kg/day; D) attenuated CS-induced freezing levels even more. Data are presented as means ± SEM. <i>n</i> = 7–10 per experimental group. ^##<i>p</i><0.01, ^###<i>p</i><0.001 drug vs. vehicle.</p

Representative microphotographs of c-Fos immunoreactivity in the amygdala.

<p>(a) Schematic diagram, based on the atlas of Franklin and Paxinos (1997), showing the amygdala at the level of −1.46 (Bregma). The square indicates the placement of grids for counting of c-Fos-positive cells in the medial nucleus of the amygdala (MeA). (b) Low magnification overview of the amygdala (−1.46) of a HAB mouse under basal conditions; Scale bar = 500 µm; (c) High magnification, bright field photomicrographs of representative sections matched for comparable rostrocaudal levels showing the distribution of c-Fos expression within the medial nucleus of the amygdala in HAB, NAB and LAB mice under basal conditions and after OA exposure. Scale bar = 100 µm;</p