Comparison of colorectal distension (CRD)-induced functional brain activation in stressed and sham rats.

<p>Statistically significant increases (red scale) and decreases (blue scale) in regional cerebral blood flow (rCBF) contrasting the subgroup receiving 60-mmHg CRD and the one receiving no distension (0-mmHg) are shown for the sham (left column) and water avoidance stress (WAS)-treated rats (middle column) over representative coronal slices of the brain template with anterior-posterior coordinates given relative to the bregma (<i>n</i> = 9 or 10/subgroup). Results of factorial analysis are also colorcoded showing regions with significant WAS x CRD interaction (right column). Abbreviations: aINS (anterior insular cortex), BL (basolateral amygdaloid n.), BM (basomedial amygdaloid n.), Cb (cerebellar lobule), Ce (central amygdaloid n.), Cg1/Cg2 (cingulate ctx. area 1/area 2), CPu (caudate putamen), fi (fimbria), Fr3 (frontal ctx. area 3), GP (globus pallidus), Hb (habenular n.), HPC (hippocampus), La (lateral amygdaloid n.), LD (laterodorsal thalamic n.), LPO (lateral preoptic area), M1 (primary motor ctx.), MD (mediodorsal thalamic n.), Me (medial amygdaloid n.), MPA (medial preoptic area), MPO (medial preoptic n., medial part), NAcc (n. accumbens), RS (retrosplenial ctx.), p1PAG(p1 periaqueductal gray), PF (parafascicular thalamic n.), pINS (posterior insular ctx.), PLH (peduncular part of lateral hypothalamus), Pir (piriform ctx.), Po (posterior thalamic n.), PrL (prelimbic ctx.), S1 (primary somatosensory ctx.), S2 (secondary somatosensory ctx.), SFi (septofimbrial n.), SO (superior olive), STIA (bed nucleus of the stria terminalis, intraamygdaloid division), STM (bed nucleus of the stria terminalis, medial division), V2 (secondary visual ctx.), VMH (ventromedial hypothalamic n.), VPL/VPM (ventral posteromedial/posterolateral thalamic n.). The left side of each coronal image represents the left side of the rodent brain.</p

6-OHDA lesions.

<p>Shown are the effect of bilateral striatal lesions on (A) lesion volume (% of striatal volume), (B) tyrosine hydroxylase (TH) staining of the striatum, (C) TH staining of the substantia nigra reticulata (SNR), and (D) TH staining of the substantia nigra compacta (SNC). #: significant difference between sham rats without exercise training (Sham/No-ET) and lesioned rats without ET (Lesion/No-ET), <i>P</i><0.05, Student’s <i>t</i> test. *: significant difference between Lesion/No-ET and Lesion/ET, <i>P</i><0.01, Student’s <i>t</i> test. The inset in (A) shows a representative TH stained coronal section showing bilateral depletion of TH (outlined in red).</p

Regions of statistically significant differences of functional subcortical activation as determined by SPM analysis.

<p>Data are for rats with bilateral striatal lesions, sham lesions, during treadmill walking or at rest, and with or without a prior history of exercise training (Groups: Lesion/Walk/No-ET, n = 9; Sham/Walk/No-ET, n = 10; Lesion/Rest/No-ET, n = 10; Sham/Rest/No-ET, n = 9; Lesion/Walk/ET, n = 11; Lesion/Rest/ET, n = 12). Significance for all entries is shown at the voxel level (P<0.05) with a minimum extent threshold of 100 contiguous voxels. ‘a’ denotes ‘anterior’ and ‘p’ denotes ‘posterior’. ‘+’ denotes increases and ‘−’ denotes decreases in the group differences in cerebral blood flow tracer distribution in the left/right hemispheres, with symbols in parentheses denoting changes less broadly represented.</p

Experimental design.

<p>Visceral motor response (VMR) to colorectal distension (CRD) was measured before (day 0, baseline) and after (day 11) water avoidance stress (WAS) or sham treatment. Each time, CRDs of 10-, 20-, 40-, and 60-mmHg (duration = 20 s, interstimulus interval = 4 min) were delivered twice for each pressure level. On day 11, following VMR measurement, cerebral blood flow (CBF) mapping was performed while the animal was receiving a 60-mmHg CRD or no distension (0-mmHg control).</p

Structurally linked functional connectivity.

<p>Structural (SC) and functional connectivity (FC) networks are combined to create a structurally linked functional connectivity (SLFC) network such that final network contains all regions that the SC and FC networks have in common. Note the SLFC network inherits directionality information (denoted with arrows) from the SC network and the sign of functional interaction (positive/red or negative/blue correlation) from the FC network.</p

Regions of statistically significant differences of functional cerebral cortical activation as determined by SPM analysis.

<p>Data are for rats with bilateral striatal lesions, sham lesions, during treadmill walking or at rest, and with or without a prior history of exercise training (Groups: Lesion/Walk/No-ET, n = 9; Sham/Walk/No-ET, n = 10; Lesion/Rest/No-ET, n = 10; Sham/Rest/No-ET, n = 9; Lesion/Walk/ET, n = 11; Lesion/Rest/ET, n = 12). Significance for all entries is shown at the voxel level (P<0.05) with a minimum extent threshold of 100 contiguous voxels. ‘a’ denotes ‘anterior’ and ‘p’ denotes ‘posterior’. ‘+’ denotes increases and ‘−’ denotes decreases in the group differences in cerebral blood flow tracer distribution in the left/right hemispheres, with symbols in parentheses denoting changes less broadly represented.</p

Training speeds during 4 weeks of forced running wheel exercise.

<p>Lesioned rats received four 5-min exercise sessions/day (2 min. intersession interval) and 5 consecutive days/week beginning 2 weeks after bilateral striatal lesioning.</p

Functional brain activation in rats with bilateral striatal lesions and sham-lesioned rats.

<p>Shown are statistically significant differences in activation during acute treadmill walking (Lesion/Walk/No-ET, <i>n</i> = 9, Sham/Walk/No-ET, <i>n</i> = 10) or at rest (Lesion/Rest/No-ET, <i>n</i> = 10, Sham/Rest/No-ET, <i>n</i> = 9). Comparison highlights lesion effects (Lesion vs. Sham) or the effect of walking (Walk vs. Rest). No exercise training (ET) was given. Depicted is a selection of representative coronal slices (anterior–posterior coordinates relative to bregma). Colored overlays show statistically significant positive (red) and negative (blue) differences. Abbreviations are those from the Paxinos and Watson rat atlas <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0080058#pone.0080058-Paxinos1" target="_blank">[39]</a>: 5 (trigeminal n., motor, sensory), aca (anterior commissures), BL (basolateral amygdalar n.), Ce (central amygdalar n.), Cg (cingulate cortex), CM (central medial thalamic n.), CPu (striatum: anterior, ant-CPu; dorsal, d-CPu; ventral, v-CPu), d-HPC (dorsal hippocampus), DP (dorsal peduncular cortex), DS (dorsal subiculum), Ect (ectorhinal cortex), Ent (entorhinal cortex), GPe (external globus pallidus), GPi (internal globus pallidus/entopeduncular n.), I (insular cortex), IC (inferior colliculus), IL (infralimbic cortex), IP (interpeduncular n.), La (lateral amygdalar n.), LO (lateral orbital cortex), LP (lateral posterior thalamic n.), LS (lateral septum), M1, M2 (primary, secondary motor cortex), Me (medial amygdalar n.), MS (medial septum), mRT (mesencephalic reticular formation), Nv (navicular n.), PaS (parasubiculum), PH (posterior hypothalamus), Pir (piriform cortex), Pn (pons), PrL (prelimbic cortex), PtA (parietal association cortex), RPC (red n.), RS (retrosplenial cortex), S1DZ, S1FL, S1J, S1Tr, S1ULp, (primary somatosensory cortex: dysgranular, forelimb, jaw, trunk, upper lip), S2 (secondary somatosensory cortex), SC (superior colliculus), SN (substantia nigra), STN (subthalamic n.), TT (tenia tecta), vermis (2^nd, 3^rd cerebellar simple lobule), V1, V2 (primary, secondary visual cortex), v-HPC (ventral hippocampus), VL (ventral lateral thalamic n.), VM (ventromedial thalamic n.), VMH (ventromedial hypothalamus), VPL/VPM (ventral posterolateral, ventral posteromedial thalamic nuclei), VP (ventral pallidum), VS (ventral subiculum), ZI (zona inserta).</p

Timeline of experiments.

<p>Timeline of experiments.</p

Effect of repeated water avoidance stress (WAS) on visceromotor response (VMR) to colorectal distension (CRD).

<p>(A) VMR measured as electromyographic (EMG) area under the curve (AUC) and expressed as % of control (baseline VMR to 60-mmHg CRD) was significantly increased following WAS on day 11 compared to day 0 baseline (<i>n</i> = 20, <i>F</i>(1, 19) = 18.19, <i>P</i><0.001, two-way repeated measures ANOVA). (B) Repeated sham procedure caused a moderate increase in VMR, primarily to 60-mmHg CRD (<i>n</i> = 18, <i>F</i>(1,17) = 4.67, <i>P</i> = 0.045, two-way repeated measures ANOVA). (C) Compared to sham-treated rats, stressed rats showed significantly greater increases in VMR after treatment (<i>F</i>(1,36) = 4.47, <i>P</i> = 0.042, mixed model ANOVA). Data are expressed as means ± SEM.</p