Perinatal high‐fat diet exposure alters oxytocin and corticotropin releasing factor inputs onto vagal neurocircuits controlling gastric motility

Abstract

Perinatal high‐fat diet (pHFD) exposure alters the development of vagal neurocircuits that control gastrointestinal (GI) motility and reduce stress resiliency in offspring. Descending oxytocin (OXT; prototypical anti‐stress peptide) and corticotropin releasing factor (CRF; prototypical stress peptide) inputs from the paraventricular nucleus (PVN) of the hypothalamus to the dorsal motor nucleus of the vagus (DMV) modulate the GI stress response. How these descending inputs, and their associated changes to GI motility and stress responses, are altered following pHFD exposure are, however, unknown. The present study used retrograde neuronal tracing experiments, cerebrospinal fluid extraction, in vivo recordings of gastric tone, motility and gastric emptying rates, and in vitro electrophysiological recordings from brainstem slice preparations to investigate the hypothesis that pHFD alters descending PVN–DMV inputs and dysregulates vagal brain–gut responses to stress. Compared to controls, rats exposed to pHFD had slower gastric emptying rates and did not respond to acute stress with the expected delay in gastric emptying. Neuronal tracing experiments demonstrated that pHFD reduced the number of PVNOXT neurons that project to the DMV, but increased PVNCRF neurons. Both in vitro electrophysiology recordings of DMV neurons and in vivo recordings of gastric motility and tone demonstrated that, following pHFD, PVNCRF–DMV projections were tonically active, and that pharmacological antagonism of brainstem CRF1 receptors restored the appropriate gastric response to brainstem OXT application. These results suggest that pHFD exposure disrupts descending PVN–DMV inputs, leading to a dysregulated vagal brain–gut response to stress. Key points Maternal high‐fat diet exposure is associated with gastric dysregulation and stress sensitivity in offspring. The present study demonstrates that perinatal high‐fat diet exposure downregulates hypothalamic–vagal oxytocin (OXT) inputs but upregulates hypothalamic–vagal corticotropin releasing factor (CRF) inputs. Both in vitro and in vivo studies demonstrated that, following perinatal high‐fat diet, CRF receptors were tonically active at NTS–DMV synapses, and that pharmacological antagonism of these receptors restored the appropriate gastric response to OXT. The current study suggests that perinatal high‐fat diet exposure disrupts descending PVN–DMV inputs, leading to a dysregulated vagal brain–gut response to stress.

Oxytocin and corticotropin‐releasing hormone exaggerate nucleus tractus solitarii neuronal and synaptic activity following chronic intermittent hypoxia

“…Interestingly, in these latter DMV studies, the addition of OT attenuates the CRH influence on inhibitory signalling. In addition, perinatal high fat diet elevates the OT decrease of GABAergic signalling due to tonic activation of CRH receptors in the DMV (Carson et al, 2023). Future studies will also be needed to identify the specific sensory modality, projection sites and cellular mechanisms of these OT+CRH interactions on their activated nTS neurons.…”