Despite a growing body of evidence showing that in utero nicotine exposure leads to aberrantdevelopment of brainstem neurons involved in the maintenance of key homeostatic functions such asbreathing the consumption of nicotine via smokeless nicotine delivery devices (e.g. e-cigaretteswater pipes nicotine patches or gum) more than doubled between 2008-2012. A particular concernis raised by recent studies showing that 30% of pregnant smokers were advised to use nicotinepatches or gum by their physician. To date the majority of the data on nicotine exposure anddevelopment of brainstem neurons has focused on how in utero exposure alters the brains of veryyoung neonatal animals. As a result we do not know if the changes observed with in utero exposureresolve or persist with maturation or worsen if exposure continues after birth. The specific objectiveof this application is to test the hypothesis that prenatal and/or postnatal exposure to nicotine altersthe structure and function of brainstem neurons that control the muscles of the tongue (hypoglossalmotor neurons XIIMNs) using an in vitro approach as well as the breathing-related control of thetongue muscles using an in vivo approach. The tongue muscles participate in breathing swallowingsuckling and mastication and therefore are critical for organismal homeostasis. A key focus iswhether abnormal development of the tongue muscle motor system is worsened if nicotine exposurecontinues after birth or if the alterations persist or are attenuated if exposure ends at weaning.Animals (rats) will be studied at key developmental time points including the early neonatal period(postnatal day 1 (P1) - P5); the putative critical period for development of brainstem neurons (P10 -P12); the end of adolescence when brain maturation is largely complete (P50 P60); and aftersexual and social maturity (4 6 months). Specific Aims: We will use neuroanatomyimmunohistochemistry patch clamp electrophysiology and in vivo plethysmography and EMGrecordings to examine how prenatal and/or postnatal nicotine exposure alters: 1) the dendritebranching pattern and the expression of inhibitory (GABA glycine) and excitatory (glutamate)neurotransmitter receptors on XIIMNs; 2) development of important neuron membrane properties(resting potential voltage threshold for spike initiation etc.) the cell's response to excitatory andinhibitory neurotransmitters; 3) development of the breathing pattern and the function of tonguemuscles during normal quiet breathing and when breathing is increased in response to an acutenicotine challenge or by increasing inspired carbon dioxide. The proposed experiments will result in acomprehensive understanding of how in utero and life-long nicotine exposure alters development ofbrainstem motoneurons that are critical for survival.