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Fig. 3 | BMC Neuroscience

Fig. 3

From: Brain size reductions associated with endothelin B receptor mutation, a cause of Hirschsprung’s disease

Fig. 3

ETB−/− mutant has reduced neural organ volume, organ growth rate, organ volume/bodyweight indices, and organ/total brain ratios. A Significant volumetric reductions in brain and constituents were detected in young ETB−/− animals. sl/sl rat has statistically smaller TB than the control rat: 443.02 mm3 versus 533.12 mm3 (df = 9, t-value = 2.82, p-value = 0.02). Similar trend was extended across the following: T-CC (163.36 mm3 versus 203.55 mm3, df = 9, t-value = 2.73, p-value = 0.02), T-CP (28.75 mm3 versus 35.84 mm3, df = 9, t-value = 2.49, p-value = 0.03), OB (15.73 mm3 versus 18.74 mm3, df = 9, t-value = 2.78, p-value = 0.02), and Pit (1.60 mm3 versus 2.09 mm3, df = 9, t-value = 2.95, p-value = 0.02). While not reaching the statistical power, measurements of Med (38.22 mm3 versus 46.27 mm3, df = 9, t-value = 1.74, p-value = 0.12), Cer (19.43 mm3 versus 22.19 mm3, df = 9, t-value = 1.30, p-value = 0.23), and S&I Col (12.51 mm3 versus 13.73 mm3, df = 9, t-value = 1.84, p-value = 0.10) also demonstrated detectable reduction in sl/sl rats. B ETB−/− rat has significantly lower growth rates across different parts of brain. Lower TBr growth rate was observed in sl/sl rat with respect to the control animal, 5.32mm3/Hr versus 5.71mm3/Hr (df = 9, t-value = 2.03, p-value = 0.07). Consistent difference between the two groups was also seen in the following: T-CC (1.96mm3/Hr versus 2.18mm3/Hr, df = 9, t-value = 2.46, p-value = 0.04), T-CP (0.34mm3/Hr versus 0.38mm3/Hr, df = 9, t-value = 2.26, p-value = 0.05), OB (0.19mm3/Hr versus 0.20mm3/Hr, df = 9, t-value = 2.23, p-value = 0.05), Med (0.46mm3/Hr versus 0.50mm3/Hr, df = 9, t-value = 1.10, p-value = 0.30), and Pit (0.019mm3/Hr versus 0.022mm3/Hr, df = 9, t-value = 2.11, p-value = 0.06). On the other hand, minimal difference between the two groups was detected in the following: Cer (0.23mm3/Hr versus 0.24mm3/Hr, df = 9, t-value = 0.19, p-value = 0.85) and S&I Col (0.15mm3/Hr versus 0.15mm3/Hr, df = 9, t-value =  − 0.55, p-value = 0.60). C ETB−/− rat has lower neural organ/bodyweight ratios, suggesting intrinsic ETB effects on brain development. sl/sl rat has lower a TBr/bodyweight ratio than that of the control group, 39.1mm3/g versus 40.12mm3/g (df = 9, t-value = 0.58, p-value = 0.57), reflecting a disproportionally larger reduction in TBr with respect to changes in its bodyweight. Similar trends were also showed in the following: T-CC (14.42mm3/g versus 15.31 mm3/g, df = 9, t-value = 1.02, p-value = 0.34), T-CP (2.53mm3/g versus 2.69 mm3/g, df = 9, t-value = 0.91, p-value = 0.39), OB (1.39mm3/g versus 1.41mm3/g, df = 9, t-value = 0.23, p-value = 0.82), Med (3.37mm3/g versus 3.48mm3/g, df = 9, t-value = 0.34, p-value = 0.74), and Pit (0.14mm3/g versus 0.16mm3/g, df = 9, t-value = 2.00, p-value = 0.08). On the other hand, sl/sl rat has slightly larger indices in the following: Cer (1.72mm3/g versus 1.67mm3/g, df = 9, t-value =  − 0.32, p-value = 0.75) and S&I Col (1.11mm3/g versus 1.03mm3/g, df = 9, t-value =  − 1.29, p-value = 0.23). Overall, ETB mutation was associated with more marked changes in the neural organs. In addition, variability in the difference of organ/bodyweight ratios between sl/sl rat and the control group suggested that the effect of ETB mutation maybe spatially dependent within the brain. D Disproportional changes in the neural organ/total brain indices of ETB−/− rat suggested non-uniform ETB effect in different parts of the brain. Subtle disproportional changes in neural constituents with respect to the global brain shrinkage were detected in sl/sl rat. Reduced organ/total brain ratios were seen in the following structures of sl/sl rat: T-CC (0.37 versus 0.38, df = 9, t-value = 1.58, p-value = 0.15), T-CP (0.065 versus 0.067, df = 9, t-value = 1.17, p-value = 0.27), Med (0.086 versus 0.087, df = 9, t-value = 0.17, p-value = 0.87), and Pit (0.0036 versus 0.0039, df = 9, t-value = 1.54, p-value = 0.16). On the contrary, organ/total-brain indices of OB (0.036 versus 0.035, df = 9, t-value = − 0.54, p-value = 0.60), Cer (0.044 versus 0.041, df = 9, t-value = − 0.75, p-value = 0.47) and S&I Col (0.029 versus 0.026, df = 9, t-value = − 1.78, p-value = 0.11) were larger in sl/sl rats. This variation in changes suggested that ETB effect may be regional dependent within the brain. TB Total Brain, T-CC Total Cerebral Cortex, T-CP  Total Caudate Putamen, OB  Olfactory Bulb, Med  Medulla, Cer  Cerebellum, S&I Col  Superior and Inferior Colliculus, Pit   Pituitary gland. *statistically significant, p-value  ≤  0.05

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