Early-life oxytocin attenuates the social deficits induced by caesarean-section delivery in the mouse

Abstract

The oxytocin (OXT) system has been strongly implicated in the regulation of social behaviour and anxiety, potentially contributing to the aetiology of a wide range of neuropathologies. Birth by Caesarean-section (C-section) results in alterations in microbiota diversity in early-life, alterations in brain development and has recently been associated with long-term social and anxiety-like behaviour deficits. In this study, we assessed whether OXT intervention in the early postnatal period could reverse C-section-mediated effects on behaviour, and physiology in early life and adulthood. Following C-section or per vaginum birth, pups were administered with OXT (0.2 or 2 μg/20 μl; s.c.) or saline daily from postnatal days 1-5. We demonstrate that early postnatal OXT treatment has long-lasting effects reversing many of the effects of C-section on mouse behaviour and physiology. In early-life, high-dose OXT administration attenuated C-section-mediated maternal attachment impairments. In adulthood, low-dose OXT restored social memory deficits, some aspects of anxiety-like behaviour, and improved gastrointestinal transit. Furthermore, as a consequence of OXT intervention in early life, OXT plasma levels were increased in adulthood, and dysregulation of the immune response in C-section animals was attenuated by both doses of OXT treatment. These findings indicate that there is an early developmental window sensitive to manipulations of the OXT system that can prevent lifelong behavioural and physiological impairments associated with mode of birth.

Fig. 1. Early-life oxytocin increases plasma oxytocin concentration in adulthood.

ASchematic representation of OXT treatment and behavioural testing sequence. Following birth by C-Section or per vaginum, pups received daily injections of OXT (0.2 or 2 μg/20 μl saline; s.c.) from postnatal days 1–5 and were subjected to a sequence of behavioural tests. B OXT administration in early-life increases OXT plasma levels in adulthood. Mode of delivery effect (F (1, 41) = 1.116, p = 0.297); treatment effect (F (1, 41) = 5.893, p = 0.006); mode of delivery × treatment (F (2,41) = 0.886, p = 0.420). ([VB control n = 6, VB 0.2 OT n = 7, VB 2 OT control n = 8, CS control n = 10, CS 0.2 OXT n = 8, CS 2 OXT n = 8]). Two-way ANOVA, followed by LSD post-hoc. OXT oxytocin, VB vaginal birth, CS C-section. Male offspring in each group derived from three independent litters.

Fig. 2. Early postnatal administration of OXT rescued C-section mediated effects on social behaviour.

AHigh-dose OXT administration reversed C-section mediated effects on attachment behaviour in early-life. VB control x²(1) = 5.261, p = 0.022, n = 23; VB 0.2 OXT x²(1) = 8.909, p = 0.003, n = 22; VB 2 OXT x²(1) = 8.333, p = 0.004, n = 12; CS control x²(1) = 0.667, p = 0.414, n = 24; CS 0.2 OXT x²(1) = 0.391, p = 0.532, n = 23; CS 2 OXT x²(1) = 4.167, p = 0.041, n = 24 (one sample Chi-square test). Data are represented as median with interquartile range; whiskers represent min and max values. Male and Female offspring. *p < 0.05 for differences within the group. B Low-dose OXT increases the number of calls followed isolation-induced USV. There was no significant effect of the mode of delivery (x² = 0.827; df = 1; p = 0.363). However, when pups were treated with low-dose OXT there was a significant increase on the number of calls emitted in both birth conditions (x² = 44.995; df = 2; p < 0.001). ([VB control n = 44, VB 0.2 OT n = 43, VB 2 OT control n = 24, CS control n = 30, CS 0.2 OXT n = 29, CS 2 OXT n = 25]). Male and Female offspring. Kruskal–Wallis test followed by Mann–Whitney U test. Data are represented as median with interquartile range; whiskers represent min and max values. ^#p < 0.05 for treatment effect within the group. C Low-dose OXT rescued the deficit in the preference for social novelty in adult CS mice. VB control t (11) = 4.681, p = 0.001, n = 12; VB 0.2 OXT t (11) = 3.064, p = 0.011, n = 12; VB 2 OXT t (10) = 3.404, p = 0.007, n = 11; CS control t (11) = 0.594, p = 0.564, n = 12; CS 0.2 OXT t (11) = 3.671, p = 0.004, n = 12; CS 2 OXT t (10) = 0.970, p = 0.355, n = 12. Male offspring. Paired Student’s t test comparing interaction time with a familiar mouse to a novel mouse. Data are represented as Mean ± Standard Error of the Mean (S.E.M.). *p < 0.05 and **p < 0.01 for mouse vs. object (A–C) Offspring in each group is derived from three independent litters. OXT oxytocin, VB vaginal birth, CS C-section.

Fig. 3. Effects of postnatal OXT administration on C-section-associated anxiety phenotype.

AEarly postnatal treatment with low-dose OXT decreased the number of marbles buried in the CS group. Mode of delivery effect (F (1, 73) = 4.716, p = 0.033); treatment effect (F (2, 73) = 2.258, p = 0.112); mode of delivery × treatment (F (2,73) = 3.351, p = 0.041) ([VB control n = 12, VB 0.2 OT n = 14, VB 2 OT control n = 13, CS control n = 15, CS 0.2 OXT n = 12, CS 2 OXT n = 13]). B OXT administration did not improve C-section-induced anxiety-like behaviour in the elevated plus maze. Mode of delivery effect (F (1, 74) = 7.614, p = 0.007); treatment effect (F (2, 74) = 0.663, p = 0.518); mode of delivery × treatment (F (2,74) = 0.820, p = 0.444). C There were no significant differences in the number of entrances of the closed arms of the EPM. Mode of delivery effect (F (1, 74) = 0.843, p = 0.361); treatment effect (F (2, 74) = 0.829, p = 0.441); mode of delivery × treatment (F (2,74) = 1.497, p = 0.231). ([VB control n = 12, VB 0.2 OT n = 14, VB 2 OT control n = 13, CS control n = 16, CS 0.2 OXT n = 12, CS 2 OXT n = 13]).C There were no significant effects on time spent in central zone of an aversive-open field. Early postnatal treatment did not reverse C-section-mediated effects on the total distance travelled in an aversive open-field arena. Time in the central zone: Mode of delivery effect (F (1, 65) = 8.167, p = 0.006); treatment effect (F (2, 65) = 2.079, p = 0.133); mode of delivery × treatment (F (2,65) = 7.848, <0.001) ([VB control n = 9 VB 0.2 OT n = 11, VB 2 OT control n = 13, CS control n = 14, CS 0.2 OXT n = 12, CS 2 OXT n = 12]). Total distance travelled: Mode of delivery effect (F (1, 65) = 5.531, p = 0.022); treatment effect (F (2, 65) = 0.713, p = 0.261); mode of delivery × treatment (F (2,65) = 2.164, p = 0.123) ([VB control n = 9 VB 0.2 OT n = 11, VB 2 OT control n = 13, CS control n = 14, CS 0.2 OXT n = 12, CS 2 OXT n = 12]). A–C Two-way ANOVA, followed by LSD post-hoc. Data are represented as Mean ± Standard Error of the Mean (S.E.M.). Male offspring in each group is derived from three independent litters. *p < 0.05, *p < 0.01 and ***p < 0.001. OXT oxytocin, VB vaginal birth, CS C-section.

Fig. 4. Early-life OXT administration induced long-lasting effects on immune function.

AEarly-life OXT attenuates TNF-α secretion in CS splenocytes stimulated with LPS. Mode of delivery effect (x² = 0.432; df = 1; p = 0.511) and treatment effect (x² = 7.994; df = 2; p = 0.018) ([VB control n = 6, VB 0.2 OT n = 5, VB 2 OT control n = 6, CS control n = 14, CS 0.2 OXT n = 6, CS 2 OXT n = 11]). B Early-life OXT decreases IL-10 secretion in CS splenocytes stimulated with LPS in CS group. Mode of delivery effect (x² = 227.000; df = 1; p = 0.177) and treatment effect (x² = 11.805; df = 2; p = 0.003) ([VB control n = 6, VB 0.2 OT n = 5, VB 2 OT control n = 8, CS control n = 14, CS 0.2 OXT n = 6, CS 2 OXT n = 11]). Kruskal–Wallis test followed by Mann–Whitney. Male offspring in each group is derived from three independent litters. Data are represented as Median ± Interquartile range. *p < 0.05 for mode of delivery effect and ^#p < 0.05 for treatment effect within the group. OXT oxytocin, VB vaginal birth, CS C-section.