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This Article Full Text Full Text (PDF) All Versions of this Article: 92/4/2548    most recent 00500.2004v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (10) Citing Articles via Google Scholar Google Scholar Articles by Huang, Z.-G. Articles by Mendelowitz, D. Search for Related Content PubMed PubMed Citation Articles by Huang, Z.-G. Articles by Mendelowitz, D.

Prenatal Nicotine Exposure Alters the Types of Nicotinic Receptors That Facilitate Excitatory Inputs to Cardiac Vagal Neurons

Department of Pharmacology and Physiology, George Washington University, Washington, DC 20037

Submitted 12 May 2004; accepted in final form 19 June 2004

Nicotinic receptors play an important role in modulating the activity of parasympathetic cardiac vagal neurons in the medulla. Previous work has shown nicotine acts via at least three mechanisms to excite brain stem premotor cardiac vagal neurons. Nicotine evokes a direct increase in holding current and facilitates both the frequency and amplitude of glutamatergic neurotransmission to cardiac vagal neurons. This study tests whether these nicotinic receptor–mediated responses are endogenously active, whether 42 and 7 nicotinic receptors are involved, and whether prenatal exposure to nicotine alters the magnitude of these responses and the types of nicotinic receptors involved. Application of neostigmine (10 µM) significantly increased the holding current, amplitude, and frequency of miniature excitatory postsynaptic current (mEPSC) glutamatergic events in cardiac vagal neurons. In unexposed animals, the nicotine-evoked facilitation of mEPSC frequency, but not mEPSC amplitude or holding current, was blocked by -bungarotoxin (100 nM). Prenatal nicotine exposure significantly exaggerated and altered the types of nicotinic receptors involved in these responses. In prenatal nicotine-exposed animals, -bungarotoxin only partially reduced the increase in mEPSC frequency. In addition, in prenatal nicotine-exposed animals, the increase in holding current was partially dependent on -7 subunit–containing nicotinic receptors, in contrast to unexposed animals in which -bungarotoxin had no effect. These results indicate prenatal nicotine exposure, one of the highest risk factors for sudden infant death syndrome (SIDS), exaggerates the responses and changes the types of nicotinic receptors involved in exciting premotor cardiac vagal neurons. These alterations could be responsible for the pronounced bradycardia that occurs during apnea in SIDS victims.

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