title: Prenatal nicotine exposure evokes changes in the incidence and degree of fetal electrocortical activation.
abstract: The effects of acute and chronic nicotine (N) administration on fetal electrocorticogram (ECoG) were investigated with spectral analysis. Fetal lambs were instrumented surgically to permit unanesthetized ECoG monitoring and N administration. Acute exposure studies used 4-hr constant-rate infusions at 0.6, 3 or 10 mg/hr. Chronic exposure studies used continuous infusions at 1.2 mg/hr for 7 days. The fast Fourier transform and several derivative parameters were used to quantitate the fetal ECoG during both control records and N infusions. Four states were identified and quantitated in the control ECoG: high-voltage slow activity (State I); low-voltage, fast activity (State IV); and two transitional states of intermediate amplitude and frequency. Acute N infusions elicited changes in the incidence and degree of electrocortical activation that were biphasically dose-related. The 0.6-mg/hr infusion evoked electrocortical activation through an increase in the incidence of State IV. Higher infusion rates elicited progressively less electrocortical activation. The 3-mg/hr infusion affected marginal activation, through a reduction in the incidence of State I. The 10-mg/hr infusion elicited mixed activation and depression, as assessed by multiple parameter changes. Desensitization of several responses diminished the magnitude of depressive effect observed during the 3- and 10-mg/hr infusions. Chronic nicotine infusions elicited progressive augmentation of electrocortical activation, through increases in the incidence and frequencies of State IV. Tolerance to this activating response was not observed.
authors.affiliation: Department of Pharmacology, Cornell University Medical College, New York.
authors.forename: M E
authors.initials: ME
authors.lastname: McNerney
authors.forename: H H
authors.initials: HH
authors.lastname: Szeto
mesh_terms: D000818:Animals; D002540:Cerebral Cortex / Q000187:drug effects* / Q000196:embryology* / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D004569:Electroencephalography / Q000187:drug effects*; D004594:Electrophysiology; D005260:Female; D005333:Fetus / Q000187:drug effects*; D009538:Nicotine / Q000633:toxicity*; D011247:Pregnancy; D012756:Sheep; D013997:Time Factors
chemical_list: D009538:Nicotine