Accelerated neuromuscular development in the rat with prenatal exposure to nicotine

Nicotine, administered to pregnant Sprague-Dawley rats either throughout gestation or during two selective prenatal periods before or after muscular innervation (i.e. before or after gestational day 13), accelerated the maturation of developing nerve and muscle as viewed in 2-week-old offspring. Prenatal treatment of rats with nicotine (tartrate salt; 0.25 mg/kg twice a day; i.p.) induced marked changes in the contractile force and speed of the developing extensor digitorum longus (EDL) muscle when tested in situ on 14 to 15-day-old pups. In all nicotine treatment groups isometric twitch and tetanus half contraction durations were shorter than controls. Use of 2,3,5-triphenyltetrazolium chloride, a biochemical indicator for cellular respiration, showed that totigestational nicotine administration increases cellular metabolic activity of EDL muscle. Hypertrophy of adrenal glands in these animals also was noted. While each of the three courses of nicotine administration accelerated muscle development and maturation, nicotine during the first half of prenatal development, prior to EDL muscle innervation, produced a more dramatic effect than nicotine during the second half of prenatal life.