TRANSPORT OF EXOGENOUS BETA-LIPOTROPIN (ß-LPH) FROM THE PITUITARY TO THE CENTRAL NERVOUS SYSTEM OF THE RAT

Abstract

This chapter describes the transport mechanism of exogenous beta-lipotropin (β-LPH) from the pituitary to the central nervous system of the rat. It discusses a study to explore the retrograde transport of β-LPH to the brain after injection of the peptide in or around the pituitary. On comparing the results of intrapituitary and intrasellar routes of administration, it is concluded that the CSF is very much involved in the transport of β-LPH to the CNS. After both types of administration, the highest uptake was seen in the median eminence-arcuate regions suggesting that this area is the first destination of the transported material. The median eminence has been reported to lack blood–brain and blood–CSF barriers. Thus, when a compound enters this region—no matter whether this occurs via vascular channels or the external CSF—it encounters the perivascular space whence it can immediately travel to the CSF, the blood, and the axon terminals of the median eminence. The special meningeal relations around the median eminence, stalk, pituitary region result in a situation where the median eminence capillaries are surrounded by the same fluid compartment as the pituitary gland itself.