The ability coordinate breathing, suckling, and swallow is required for survival at birth. Infants with prenatal
exposure to opioids can have abnormalities in swallow efficiency and swallow-breathing coordination, sensory-
motor responses to pharyngeal stimulus, and esophageal motility reflexes, which often results in persistent
feeding difficulties. The swallow pattern generator is located within the brainstem, but it has been difficult to
study due to its location and widely dispersed neural circuits. Our preliminary studies describe a novel method
that allows for the visualization and recording of a vast number of neurons along the intermediate zone of the
medial reticular formation and Nucleus Ambiguus (NA), while preserving the Nucleus Tractus Solitarius. We
demonstrate reliable central stimulation of swallow with simultaneous optical recording of neurons in the
semicompact and compact regions of the NA, along with nerve root recordings. Activation of NA neurons
during swallow is affected by prenatal opioid exposure. Our methods also allow superimposition of optical
recordings onto subsequent immunohistochemical images to identify regional cellular phenotypes and to
confirm recording locations. Our working hypothesis is that the brainstem swallow network spans the medulla
and is vulnerable to opioids. The current application has evolved from collaborative work from two established
investigators, bringing together expertise in central neural circuitry, optical/ histological techniques, and
regulation of swallow. The proposed studies are designed to describe location and type of neurons active
during swallow, alterations when swallow is stimulated across the respiratory cycle, and the impact of neonatal
opioid withdrawal syndrome. The combined state-of-the-art techniques will provide much-needed mechanistic
insight into swallow and clinical observation of infants with neonatal opioid withdrawal syndrome (NOWS).