Evaluation of Sensory Evoked Potentials in Long Evans Rats Gestationally Exposed to Mercury (Hg0) Vapor

• Published in: Toxicological sciences 2004-11, Vol.82 (1), p.193-206
• Main Authors: Herr, David W., Chanda, Sushmita M., Graff, Jaimie E., Barone, Stanley S., Beliles, Robert P., Morgan, Daniel L.
• Format: Article
• Language: English
• Subjects: Administration, Inhalation; Animals; Animals, Newborn; Birth Weight - drug effects; Body Weight - drug effects; Electrophysiology; evoked potentials; Evoked Potentials, Somatosensory - drug effects; Evoked Potentials, Somatosensory - physiology; Evoked Potentials, Visual - drug effects; Evoked Potentials, Visual - physiology; Female; Male; Mercury - administration & dosage; Mercury - toxicity; Mercury Poisoning; mercury vapor; Organogenesis - drug effects; Peripheral Nervous System - drug effects; Peripheral Nervous System - embryology; Peripheral Nervous System - growth & development; Pregnancy; Prenatal Exposure Delayed Effects; Rats; Rats, Long-Evans; sensory toxicity; Volatilization
• ISSN: 1096-6080; 1096-0929; 1096-0929
• DOI: 10.1093/toxsci/kfh246

Mercury is known to alter neuronal function and has been shown to cross the placental barrier. These experiments were undertaken to examine if gestational exposure to mercury vapor (Hg0) would result in alterations in sensory neuronal function in adult offspring. Dams were exposed to 0 or 4 mg/m3 Hg0 for 2 h/day from gestational days 6–15. This exposure paradigm has been shown to approximate a maximal tolerated dose of Hg0 for the dams. Between postnatal days 140–168, male and female offspring (one of each gender/dam) were examined using a battery of sensory evoked potentials. Peripheral nerve action potentials, nerve conduction velocity, somatosensory evoked responses (cortical and cerebellar), brainstem auditory evoked responses, pattern evoked potentials, and flash evoked potentials were quantified. Gestational exposure to 4 mg/m3 Hg0 did not significantly alter any of the evoked responses, although there was a suggestion of a decrease in compound nerve action potential (CNAP) amplitudes in male animals for the 3 mA stimulus condition. However, this possible change in CNAP amplitudes was not replicated in a second experiment. All evoked potentials exhibited predictable changes as the stimulus was modified. This shows conclusively that the evoked responses were under stimulus control, and that the study had sufficient statistical power to detect changes of these magnitudes. These results indicate that gestational exposure to 4 mg/m3 Hg0 did not result in changes in responses evoked from peripheral nerves, or the somatosensory, auditory, or visual modalities.