CHANGES IN PERIPHERAL NERVOUS-SYSTEM ACTIVITY PRODUCED IN RATS BY PRENATAL EXPOSURE TO CARBON-MONOXIDE

The present experiments were designed to investigate whether alteratio ns of peripheral nervous system activity may be produced in male Wista r rats by prenatal exposure (from day 0 to day 20 of pregnancy) to rel atively low levels of CO (75 and 150 ppm). The voltage clamp analysis of ionic currents recorded from sciatic nerve fibres showed that prena tal exposure to CO produced modifications of sodium current properties . In particular, in 40-day-old rats exposed to CO (75 and 150 ppm) dur ing gestation, the inactivation kinetics of transient sodium current w ere significantly slowed. Analysis of the potential dependence of stea dy-state Na inactivation, h(infinity) (V), showed that the percentage of the maximum number of activatable Na channels at the normal resting potential (-80 mV) was increased to almost-equal-to 85% in CO-exposed rats. Moreover, the voltage-current relationship showed a negative sh ift of sodium equilibrium potential in CO treated animals. In 270-day- old CO-exposed rats, parameters of sodium inactivation were not signif icantly modified; the reversal potential was still lower with respect to controls. The results indicate that prenatal exposure to mild CO co ncentrations produces reversible changes in sodium inactivation kineti cs and on irreversible change in sodium equilibrium potential. These a lterations could reflect CO influence on the rate of ion channel devel opment.