Post-weaning social isolation modifies neonatal anoxia-induced changes in energy metabolism and growth of rats

Neonatal oxygen deficiency in rats may disturb growth and long-term metabolic homeostasis. In order to facilitate metabolic evaluation, the subjects are usually housed individually. However, social isolation associated with individually housed conditions alters animal behavior, which may influence the experimental results. This study investigated the effects of social isolation on neonatal anoxia-induced changes in growth and energy metabolism. Male and female Wistar rats were exposed, on postnatal day 2 (P2), to either 25-min of anoxia or control treatment. From P27 onward, part of the subjects of each group was isolated in standard cages, and the remaining subjects were housed in groups. At P34 or P95, the subjects were fasted for 18 h, refeed for 1 h, and then perfused 30 min later. Glycemia, leptin, insulin, and morphology of the pancreas were evaluated at both ages. For subjects perfused at P95, body weight and food intake were recorded up to P90, and the brain was collected for Fos and NeuN immunohistochemistry. Results showed that male rats exposed to neonatal anoxia and social isolation exhibited increased body weight gain despite the lack of changes in food intake. In addition, social isolation (1) decreased post-fasting weight loss and post-fasting food intake and (2) increased glycemia, insulin, and leptin levels of male and female rats exposed to anoxia and control treatments, both at P35 and P95. Furthermore, although at P35, anoxia increased insulin levels of males, it decreased the area of the β-positive cells in the pancreas of females. At P95, anoxia increased post-prandial weight loss of males, post-fasting food intake, insulin, and leptin, and decreased Fos expression in the arcuate nucleus (ARC) of males and females. Hyperphagia was associated with possible resistance to leptin and insulin, suspected by the high circulating levels of these hormones and poor neuronal activation of ARC. This study demonstrated that continuous social isolation from weaning modifies, in a differentiated way, the long-term energy metabolism and growth of male and female Wistar rats exposed to neonatal anoxia or even control treatments. Therefore, social isolation should be considered as a factor that negatively influences experimental results and the outcomes of the neonatal injury. These results should also be taken into account in clinical procedures, since the used model simulates the preterm babies' conditions and some therapeutic approaches require isolation.

Pcdh11x controls target specification of mossy fiber sprouting

Circuit formation is a defining characteristic of the developing brain. However, multiple lines of evidence suggest that circuit formation can also take place in adults, the mechanisms of which remain poorly understood. Here, we investigated the epilepsy-associated mossy fiber (MF) sprouting in the adult hippocampus and asked which cell surface molecules define its target specificity. Using single-cell RNAseq data, we found lack and expression of Pcdh11x in non-sprouting and sprouting neurons respectively. Subsequently, we used CRISPR/Cas9 genome editing to disrupt the Pcdh11x gene and characterized its consequences on sprouting. Although MF sprouting still developed, its target specificity was altered. New synapses were frequently formed on granule cell somata in addition to dendrites. Our findings shed light onto a key molecular determinant of target specificity in MF sprouting and contribute to understanding the molecular mechanism of adult brain rewiring.

Neonatal anoxia increases nociceptive response in rats: Sex differences and lumbar spinal cord and insula alterations

Neonatal anoxia is a well-known world health problem that results in neurodevelopmental deficits, such as sensory alterations that are observed in patients with cerebral palsy and autism disorder, for which oxygen deprivation is a risk factor. Nociceptive response, as part of the sensory system, has been reported as altered in these patients. To determine whether neonatal oxygen deprivation alters nociceptive sensitivity and promotes medium- and long-term inflammatory feedback in the central nervous system, Wistar rats of around 30 h old were submitted to anoxia (100% nitrogen flux for 25 min) and evaluated on PND23 (postpartum day) and PND90. The nociceptive response was assessed by mechanical, thermal, and tactile tests in the early postnatal and adulthood periods. The lumbar spinal cord (SC, L4-L6) motor neurons (MNs) and the posterior insular cortex neurons were counted and compared with their respective controls after anoxia. In addition, we evaluated the possible effect of anoxia on the expression of astrocytes in the SC at adulthood. The results showed increased nociceptive responses in both males and females submitted to anoxia, although these responses were different according to the nociceptive stimulus. A decrease in MNs in adult anoxiated females and an upregulation of GFAP expression in the SC were observed. In the insular cortex, a decrease in the number of cells of anoxiated males was observed in the neonatal period. Our findings suggest that oxygen-deprived nervous systems in rats may affect their response at the sensorimotor pathways and respective controlling centers with sex differences, which were related to the used stimulus.