Electronmicroscopic study of the effect of 6-an on the sciatic nerve in newborn rats.

12 hrs, 1, 2, and 4 days after i.p. administration of 2, 3 or 5 mg/kg 6-AN (6-Aminonicotinamide) on postnatal day 5, the following findings were made in the sciatic nerve of the newborn rat. In the myelin-forming fibres a swelling between the axolemm and the first inner intraperiod-line of the Schwann cell develops with displacement of the otherwise intact axon. The myelin formation is not impeded. During the 4 days of control after administration of 6-AN there is continual growth of the myelin sheath with an orderly lamellar structure. Using any dose there is no demonstrable alteration in the Schwann cells--with the exception of the inner cytoplasmic tongue--either in the foetal promyelin and mature nonmyelinated fibres. These findings are discussed and compared with the known glia alterations of the spinal ganglia and dorsal radix after the application of 6-AN.