Site-Specific Regulation of Stress Responses Along the Rostrocaudal Axis of the Insular Cortex in Rats

Figures

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  FIGURE 1. Location of the subregions along the rostrocaudal axis of the insular cortex (IC). (Top) Photomicrograph of coronal brain sections depicting the microinjection sites of representative animals (left hemisphere) and diagrammatic representations modified from the rat brain atlas of Paxinos and Watson (1997) (right hemisphere) indicating the anterior [interaural (IA) 12.7 mm], rostral posterior (IA 9.7 mm), and caudal posterior (IA 7.6 mm) subregions of the IC. Arrows and red squares indicate the microinjection site and IC region. (Bottom) Representation of a sagittal section of the rat brain modified from the rat brain atlas of Paxinos and Watson (1997) indicating the position of the anterior (12.7 mm), rostral posterior (9.7 mm), and caudal posterior (7.6 mm) subregions of the IC along the rat brain. The numbers indicate the IA distance.

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  FIGURE 2. Effect of restraint stress on the number of Fos-positive cells along the rostrocaudal axis of the insular cortex (IC) (A). Representative coronal sections indicating the IC locations where the Fos-positive cells were quantified (B). Representative coronal sections showing Fos-positive cells of representative animals in the anterior (left), rostral posterior (middle), and caudal posterior (right) subregions of the IC in control animals (top) and rats subjected to an acute 60-min session of restraint stress (bottom). (C–E) Number of Fos-positive cells in the anterior (C), rostral posterior (D), and caudal posterior (E) regions of the IC in control animals (white bars, n = 8) and rats subjected to an acute 60-min session of restraint stress (black bars, n = 9). The bars represent the mean ± SEM. *p < 0.05, Student’s t-test.

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  FIGURE 3. Effect of bilateral microinjection of the non-selective synaptic inhibitor CoCl2 into the anterior subregion of the insular cortex (IC) on mean arterial pressure (MAP), heart rate (HR), and tail skin temperature responses evoked by an acute 60-min session of restraint stress. (A–C) Time-course curves of changes on MAP (Δ MAP), HR (Δ HR), and tail skin temperature (Δ tail skin temperature) evoked by acute restraint stress in animals treated bilaterally into the anterior subregion of the IC with vehicle (saline, 100 nl, n = 8) or the non-selective synaptic inhibitor CoCl2 (1 mM/100 nl, n = 9). Shaded area indicates the restraint stress period. Circles represent the mean ± SEM. Two-way ANOVA. (D–F) Mean of Δ MAP, Δ HR, and Δ tail skin temperature during the restraint and recovery periods in animals treated bilaterally into the anterior IC with vehicle (n = 8) or CoCl2 (n = 9). Bars represent the mean ± SEM. Two-way ANOVA.

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  FIGURE 4. Effect of bilateral microinjection of the non-selective synaptic inhibitor CoCl2 into the rostral posterior subregion of the insular cortex (IC) on mean arterial pressure (MAP), heart rate (HR), and tail skin temperature responses evoked by an acute 60-min session of restraint stress. (A–C) Time-course curves of changes on MAP (Δ MAP), HR (Δ HR), and tail skin temperature (Δ tail skin temperature) evoked by acute restraint stress in animals treated bilaterally into the rostral posterior IC with vehicle (saline, 100 nl, n = 11) or the non-selective synaptic inhibitor CoCl2 (1 mM/100 nl, n = 12). Circles represent the mean ± SEM. #p < 0.05 over the entire restraint and recovery period compared to vehicle group. Two-way ANOVA. (D–F) Mean of Δ MAP, Δ HR, and Δ tail skin temperature during the entire restraint and recovery periods in animals treated bilaterally into the rostral posterior IC with vehicle (n = 11) or CoCl2 (n = 12). Bars represent the mean ± SEM. *p < 0.05 compared to vehicle group. Two-way ANOVA followed by Bonferroni post-hoc test.

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  FIGURE 5. Effect of bilateral microinjection of the non-selective synaptic inhibitor CoCl2 into the caudal posterior subregion of the insular cortex (IC) on mean arterial pressure (MAP), heart rate (HR), and tail skin temperature responses evoked by an acute session of restraint stress. (A–C) Time-course curves of changes on MAP (Δ MAP), HR (Δ HR), and tail skin temperature (Δ tail skin temperature) evoked by acute restraint stress in animals treated bilaterally into the caudal posterior IC with vehicle (saline, 100 nl, n = 10) or the non-selective synaptic inhibitor CoCl2 (1 mM/100 nl, n = 9). Shaded area indicates the restraint stress period. Circles represent the mean ± SEM. #p < 0.05 over the entire restraint and recovery period compared to vehicle group. Two-way ANOVA. (D–F) Mean of Δ MAP, Δ HR, and Δ tail skin temperature during the entire restraint and recovery periods in animals treated bilaterally into the caudal posterior IC with vehicle (n = 10) or CoCl2 (1 nmol/100 nl, n = 9). Bars represent the mean ± SEM. *p < 0.05 compared to vehicle group. Two-way ANOVA followed by Bonferroni post-hoc test.