Prenatal nicotine exposure with continued exposure through breast milk over the 
first week of life (developmental nicotine exposure, DNE) alters the development 
of brainstem circuits that control breathing. Here, we test the hypothesis that 
DNE alters the respiratory motor response to endogenous and exogenous 
acetylcholine (ACh) in neonatal rats. We used the brainstem-spinal cord 
preparation in the split-bath configuration, and applied drugs to the brainstem 
compartment while measuring the burst frequency and amplitude of the fourth 
cervical ventral nerve roots (C4VR), which contain the axons of phrenic 
motoneurons. We applied ACh alone; the nicotinic acetylcholine receptor (nAChR) 
antagonist curare, either alone or in the presence of ACh; and the muscarinic 
acetylcholine receptor (mAChR) antagonist atropine, either alone or in the 
presence of ACh. The main findings include: (1) atropine reduced frequency 
similarly in controls and DNE animals, while curare caused modest slowing in 
controls but no consistent change in DNE animals; (2) DNE greatly attenuated the 
increase in C4VR frequency mediated by exogenous ACh; (3) stimulation of nAChRs 
with ACh in the presence of atropine increased frequency markedly in controls, 
but not DNE animals; (4) stimulation of mAChRs with ACh in the presence of 
curare caused a modest increase in frequency, with no treatment group 
differences. DNE blunts the response of the respiratory central pattern 
generator to exogenous ACh, consistent with reduced availability of functionally 
competent nAChRs; DNE did not alter the muscarinic control of respiratory motor 
output. © 2016 Wiley Periodicals, Inc. Develop Neurobiol 76: 1138-1149, 2016.