Paternal exposure to chlorpyrifos disrupts protein regulation and abolishes PKCβ signaling in learning‑related neural circuits

Environmental exposures prior to conception are increasingly recognized as modulators of offspring neurodevelopment; however, their functional impact on specific neural circuits remains poorly understood. In the present study, we investigated whether paternal preconception exposure to the neuroteratogen chlorpyrifos induces protein-level and functional alterations in learning-related brain regions of the offspring. Using a chicken (Gallus gallus domesticus) model, we examined the intermediate medial mesopallium (IMM), hippocampal subregions, and lateral striatum, focusing on protein expression of markers associated with neuroplasticity and cholinergic-mediated activation/translocation of protein kinase C beta (PKCβ), a key regulator of synaptic plasticity. Structural endpoints, including neuronal cell counts and dendritic morphology, were also assessed. A pre-hatch exposure paradigm was included for comparison. Paternal exposure resulted in region- and sex-specific alterations in protein expression, including changes in GDNF, DCX, FOS, and MAP2, predominantly in the lateral striatum and IMM, without corresponding transcriptional changes. Notably, no significant alterations were observed in neuronal cell counts or dendritic structure. In contrast, a robust functional deficit was identified, as paternal exposure completely abolished cholinergic-mediated PKCβ activation/translocation, an effect also observed following pre-hatch exposure. These findings demonstrate that paternal preconception exposure is associated with selective alterations in protein expression and impaired cholinergic-mediated PKCβ signaling within learning-related neural circuits, in the absence of overt structural damage. The dissociation between transcriptional and translational outcomes indicates that regulatory processes acting beyond transcription may contribute to the observed phenotype. Further studies are required to determine the underlying mechanisms and functional consequences of these changes.