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.
Department of Medical Physiology, Faculty of Medicine, Belgrade, Yugoslavia.
B V
BV
Zlokovic
M B
MB
Segal
H
H
Davson
M N
MN
Lipovac
S
S
Hyman
J G
JG
McComb
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