Impact of neonatal NOS-1 inhibitor exposure on neurobehavioural measures and prefrontal-temporolimbic integration in the rat nucleus accumbens.

Nitric oxide (NO) is a gaseous neurotransmitter that plays a significant role in the establishment and refinement of functional neural circuits. Genetic and post-mortem studies have suggested that neuronal NO synthase (NOS-1) activity may be compromised in frontal and temporal lobes, and related structures, in schizophrenia. The goal of this study was to determine if there is a link between neonatal disruptions in NO signalling and disturbances in the development and function of prefrontal-temporolimbic circuits. Neonatal rats were injected on postnatal days PD3-5 with the selective NOS-1 inhibitor Nω-propyl-L-arginine (NPA) and tested in adulthood (≥PD60) or as juveniles (PD30). Adult rats treated with NPA as neonates exhibited increased amphetamine-induced locomotion compared to animals receiving vehicle as neonates, whereas this was not observed in juvenile rats treated with NPA as neonates. Adult rats exposed to NPA as neonates also exhibited deficits in social interaction and short-term recognition memory, as well as reduced brain weight, compared to vehicle-treated controls. Finally, neonatal NPA exposure increased the responsiveness of nucleus accumbens neurons to prefrontal cortical input and disrupted the modulation of cortico-accumbens circuits by hippocampal afferents that is normally observed in adult animals. These results show for the first time that neonatal inhibition of NOS-1 during a critical neurodevelopmental period leads to aberrant behaviours that manifest in adulthood, as well as electrophysiological abnormalities in prefrontal-temporolimbic circuits. Greater understanding of the role of NOS-1 in the development of these circuits will shed light on how developmental insults translate to pathophysiology associated with schizophrenia.