Circulating neuroactive peptides and the blood-brain and blood-cerebrospinal fluid barriers.
Interactions of radiolabelled circulating neuroactive peptides: enkephalin-leucine (Enk-Leu), delta sleep inducing peptide (DSIP), thyrotropin-releasing hormone (TRH) and vasopressin-arginine (VP-Arg) with the blood-brain and blood-cerebrospinal fluid barriers were studied by mean of: 1. a vascular perfusion technique in the guinea-pig using multiple-time brain uptake analysis, 2. a vascular perfusion technique of the in situ isolated choroid plexus from sheep using single-circulation paired-tracer dilution or steady-state analysis. It has been demonstrated that Enk-Leu, DSIP and VP-Arg were taken up intact at the luminal side of the blood-brain barrier and blood-tissue interface of the blood-cerebrospinal fluid barrier by a saturable mechanism. On the other hand, a non-saturable mechanism as well as possible enzymatic degradation were shown during TRH interactions with either the blood-brain or blood-cerebrospinal fluid barriers. It is concluded that both, facilitated and simple diffusion, govern circulating neuroactive peptide uptake into the central nervous system.
Zlokovic
B V
BV
Department of Medical Physiology, Faculty of Medicine, Belgrade, Yugoslavia.
Segal
M B
MB
Davson
H
H
Lipovac
M N
MN
Hyman
S
S
McComb
J G
JG
D000818:Animals; D001812:Blood-Brain Barrier / Q000502:physiology*; D002250:Carbon Radioisotopes; D002831:Choroid Plexus / Q000378:metabolism; D005260:Female; D006168:Guinea Pigs; D008297:Male; D009479:Neuropeptides / Q000097:blood*; D010477:Perfusion; D011865:Radioisotope Dilution Technique; D012756:Sheep; D014316:Tritium
D002250:Carbon Radioisotopes; D009479:Neuropeptides; D014316:Tritium