Postnatal Oxytocin Treatment and Cognitive Function in Fragile X

Autism Spectrum Disorder (ASD) is a prevalent and heterogeneous neurodevelopmental disorder with high co- morbidity for intellectual disability. This includes difficulties forming episodic, personal narrative, memories that are critical for orderly thinking and organizing future behaviors. Episodic memory deficits are thus thought to be major contributors to cognitive difficulties associated with autism. Many brain changes underlying abnormalities in ASD appear in childhood suggesting the possibility for effective therapeutic strategies targeting brain maturation. One candidate therapeutic is the hypothalamic peptide Oxytocin (OXT). Postnatal OXT treatment improves social behavior in animal models of ASDs and recent work indicates that treatment in childhood improves social interactions in autistic individuals. OXT acutely facilitates forms of synaptic plasticity, but there has been little experimental consideration of possible enduring effects of postnatal OXT treatment on learning and no analyses of effects on episodic memory. We examined this possibility using intranasal OXT (iOXT) treatment in the Fmr1 KO mouse model of Fragile X Syndrome, and novel paradigms for analyses of `What, When and Where' encoding. Our preliminary results show that in Fmr1 KOs iOXT treatments during the second postnatal week (P7-13) fully rescue hippocampal field CA1 long-term potentiation, object location memory, object identity (What) learning, and social recognition as assessed in adulthood (i.e., >40d after the last treatment). These findings raise the exciting possibility that a limited period of early life OXT treatment can effect a life-long rescue of a critical element of cognitive function in ASD. They also raise questions as to the breadth of effects iOXT has on behavior and the mechanisms involved; these questions will be addressed in the proposed studies. Aim 1 studies will test if postnatal iOXT treatment of male and female Fmr1 KO mice rescues encoding for the three major components of episodic memory, social recognition and stereotypic behavior as assessed in adulthood, and if effects depend on native OXT efflux. We will also determine if there is a critical period for enduring iOXT effects on behavior. Aim 2 will use electrophysiological recordings of evoked responses and network activity, analyses of synaptic proteins and signaling, and measures of neuronal arbors to test if postnatal iOXT treatment normalizes neurobiological processes in the distinct hippocampal subdivisions related to episodic memory encoding. Finally, Aim 3 will test the hypothesis that early life iOXT leads to activation of synaptic trophic factor receptors (EGFR, TrkB) in hippocampus, thereby suggesting a direct route for OXT effects on maturational changes in the structure. Overall, the proposed studies will greatly expand our current knowledge of OXT actions in the young brain, including potentially critical roles in regulating hippocampal development and synaptic function. Moreover, the results will lay the groundwork for designing novel, early life regimens to optimize hippocampal maturation and function, and to rescue the encoding of episodic memories in ASD and related developmental disorders.