Permeability of the abdominal nerve cord of the American cockroach to fatty acids

Abstract

The rates of influex of 14C-labelled fatty acids into the abdominal nerve cord of the cockroach Periplaneta americana L. are directly correlated with their octanol/water partition coefficients. Low temperature and exposure to 2,4-dinitrophenol decrease the rate of influx slightly. It is suggested that influx of the acids into the abdominal nerve cord is due to simple diffusion facilitated by the acid's high lipid solubility and the involvement of these acids in the normal metabolism of nerve tissue. Efflux of these acids is characterized by a two-stage process with simultaneous rapid and slow phases. The fast phase is 30 times faster than the slow one. It is suggested that the rapid phase involves the efflux of a pool confined to the extracellular spaces, whereas the slow efflux is that of acids from intracellular spaces within the perineurium. The nerve sheath offers a resistance to efflux of the anions of about 13 times that which it offers to glucose. However, a much larger barrier is offered by the neuronal and glial cell membranes that regulate the movement of these acids within the cord.