title: Scintigraphic imaging with 123I-metaiodobenzylguanidine as a marker of cardiac adrenergic neurotransmission in the rat.
abstract: This study was performed to determine if 123I-metaiodobenzylguanidine (123I-MIBG) could be used to create scintigraphic images of the rat heart and to determine if this method could be used to estimate cardiac norepinephrine turnover in the intact animal. Male F344 rats were injected i.v. with 200-350 muCi of 123I-MIBG. Beginning at 5 min after the injection, scintigraphic images were made every 30 min for 5 h. The half-life of 123I-MIBG retention within the heart during the 5 h of the experiment was determined by plotting the log of the counts for each image vs. time. The half-life of cardiac 123I-MIBG was 3.44 +/- 0.17 h with a rate constant of 0.21 +/- 0.01 (hr-1). In a separate experiment, methacholine, a parasympathomimetic agonist, was given after the injection of 123I-MIBG and increased 123I-MIBG efflux. Cardiac 123I-MIBG uptake was reduced by 65% in rats sympathetically denervated with 6 hydroxy dopamine indicating that 123I-MIBG is accumulating for the most part in adrenergic nerve terminals. We conclude that scintigraphic imaging with 123I-MIBG may be a useful procedure for estimating cardiac adrenergic nervous system activity in the intact animal.
mesh_terms: D019797:3-Iodobenzylguanidine; D000818:Animals; D003287:Contrast Media; D006207:Half-Life; D006321:Heart / Q000000981:diagnostic imaging* / Q000187:drug effects / Q000294:innervation*; D007457:Iodine Radioisotopes; D007462:Iodobenzenes; D008297:Male; D016210:Methacholine Chloride / Q000494:pharmacology; D009206:Myocardium / Q000378:metabolism; D009638:Norepinephrine / Q000378:metabolism; D010277:Parasympathomimetics / Q000494:pharmacology; D011877:Radionuclide Imaging; D051381:Rats; D011916:Rats, Inbred F344; D013564:Sympathetic Nervous System / Q000187:drug effects / Q000502:physiology*; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology*
chemical_list: D003287:Contrast Media; D007457:Iodine Radioisotopes; D007462:Iodobenzenes; D010277:Parasympathomimetics; D016210:Methacholine Chloride; D019797:3-Iodobenzylguanidine; D009638:Norepinephrine