Figure 6. Intranasal administration of an EDNRB agonist rescues the myelin sheath number reduction caused by social isolation.

(A) Timeline for the intranasal experiment. At postnatal day 21 male mice were housed on their own in isolation. Mice were given two daily administrations of saline or EDNRB agonist BQ3020 from P21-P30. Mice were analysed at P35. (B) Time spent within 2.5 cm of non-social container: Saline 57.42 s ± 24.44 n = 12, BQ3020 41.44 ± 17.43 n = 17 and social container: Saline 75.82 s ± 13.26 n = 12, BQ3020 84.96 s ± 37.20 n = 17 (mean ± standard deviation). T-test. (C) Quantification of CNP positive cells in medial prefrontal cortex layers II/III: Saline 7278 ± 1165 n = 3 mice, BQ3020 9142 ± 713.3 n = 3 mice (mean ± standard error) and layer V: Saline 17114 ± 2750 n = 5 mice, BQ3020 16154 ± 1980 n = 4 mice (mean ± standard error). (D) Mean number of myelin sheath formed by oligodendrocytes per mouse. Saline 39.54 ±0.4301 n = 4 mice, BQ3020 47.29 ± 1.687 n = 4 mice (mean ± standard error). Mann-Whitney test, p=0.0286. (E) Pooled data for number of myelin sheaths formed by layer II/III medial prefrontal cortex oligodendrocytes. Saline 39.54 ±6.973 n = 28 cells from four mice, BQ3020 47.29 ± 10.18 n = 28 cells from seven mice (mean ± standard deviation). Mann-Whitney test, p=0.0019.

Figure 6—figure supplement 1. Intranasal administration of EDNRB agonist BQ3020 does not affect myelin sheath length.

(A) Distance travelled by mice during 5 minutes of exploration of the social interaction assay. Saline 17.48 meters ± 2.697 n = 12 mice, BQ3020 17.13 meters ± 35.209 n = 17 mice (mean ± standard deviation). (B) Maximum speed travelled by mice during 5 min of exploration of the social interaction assay. Saline 0.2769 ± 0.03276 n = 12 mice, BQ3020 0.2773 meters ± 0.05085 n = 17 mice (mean ± standard deviation). (C) Mean myelin sheath length formed by oligodendrocytes per mouse. Saline 59.38 µm ± 4.831 n = 28 cells from four mice, BQ3020 53.98 µm ± 5.748 n = 28 cells from four mice (mean ± standard deviation). (D) Frequency distribution of myelin sheath lengths.

Figure 6—figure supplement 2. Proposed model for how EDNRB regulates myelin sheath number.

(A) Summary of results from paper. In a social environment, EDN from the vasculature increases myelin sheath number in the medial prefrontal cortex, influencing sociability. In social isolation vascular EDN production is reduced, leading to a decreased number of myelin sheaths formed by oligodendrocytes and reduced sociability. Oligodendroglial knock out of EDNRB reduces the number of myelin sheaths formed by oligodendrocytes and reduced sociability. (B) Proposed hypothesis for how EDN signalling links neuronal activity to increased myelination and thus support of active axons. 1. Increased local neuronal activity signals to the vasculature to increase blood flow to the active area 2. The increased blood flow stimulates EDN production from endothelial cells 3. Increased EDN levels leads to the formation of more myelin sheaths by oligodendrocytes. Figures created with Biorender.