The chronic infusion of nicotine into the developing chick embryo does not alter the density of (-)-[3H]nicotine-binding sites or vestibular function.
(-)-Nicotine (1.2 mg/day) or saline was infused into chick embryos (Gallus domesticus) for 10 days beginning 12 h beyond the eight day of incubation (E8 + 12 h). Twelve h beyond the eighteenth day of incubation (E18 + 12 h), the eggs were opened to access the embryos and subcutaneous skull electrodes placed. Short latency vestibular response thresholds and input/output functions were determined to assess neurophysiological consequences of chronic nicotine administration. Samples of serum and extraembryonic (amniotic and albumen) fluid were analyzed by gas chromatography-mass spectrometry to determine the levels of nicotine and its major metabolite, cotinine. The brains were removed and divided into diencephalon and mesencephalon and the density of (-)-[3H]nicotine binding sites in each brain area was measured. Nicotine and cotinine were found in the serum and extraembryonic fluid, but nicotinic receptors were not up-regulated in the brains of animals infused with nicotine in comparison to controls. Vestibular response thresholds also did not differ between nicotine-treated and control animals.
Roll
R L
RL
College of Dentistry, University of Nebraska Medical Center, Lincoln, NE 68583.
Jones
T A
TA
Benowitz
N L
NL
Morley
B J
BJ
D000818:Animals; D002642:Chick Embryo / Q000502:physiology*; D003367:Cotinine / Q000378:metabolism; D004594:Electrophysiology; D009474:Neurons / Q000187:drug effects / Q000502:physiology; D009538:Nicotine / Q000378:metabolism* / Q000494:pharmacology*; D011978:Receptors, Nicotinic / Q000187:drug effects / Q000378:metabolism*; D013574:Synaptosomes / Q000187:drug effects / Q000378:metabolism; D014316:Tritium; D014722:Vestibule, Labyrinth / Q000378:metabolism / Q000502:physiology*
D011978:Receptors, Nicotinic; D014316:Tritium; D009538:Nicotine; D003367:Cotinine