Limitations to effect of alpha-MSH on permeability of blood-brain barrier to IV 99mTc-pertechnetate.
The effects of several variables on the permeability of the blood-brain barrier (BBB) to 99mTc-labeled sodium pertechnetate after IV administration of alpha-MSH were investigated. Doses of alpha-MSH of about 200 micrograms/kg were generally more effective in increasing the brain:blood ratio of radioactivity than the smaller doses that had previously been shown to affect behavior and the EEG. Pulsatile administration of a total of 200 micrograms/kg alpha-MSH over 90 min did not change the permeability of the BBB to the pertechnetate anion. Infusion of the same dose over 90 min significantly increased the brain:blood ratio of radioactivity in one of two experiments: no significant effects were seen with infusion for shorter times, lower concentrations, or with a 4-9 analog (Org 2766). In another experiment, bolus injection of 200 micrograms/kg alpha-MSH resulted in a significantly increased ratio 90 min later as compared with controls. Although the effects of a peptide on the permeability of the BBB to other compounds remains intriguing, limitations appear to exist in experiments with 99mTc-pertechnetate.
D000818:Animals; D001812:Blood-Brain Barrier / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D008297:Male; D009074:Melanocyte-Stimulating Hormones / Q000494:pharmacology*; D051381:Rats; D013670:Sodium Pertechnetate Tc 99m; D013667:Technetium / Q000378:metabolism*
D013667:Technetium; D009074:Melanocyte-Stimulating Hormones; D013670:Sodium Pertechnetate Tc 99m