METAIODOBENZYLGUANIDINE AS AN INDEX OF THE ADRENERGIC NERVOUS-SYSTEM INTEGRITY AND FUNCTION

  • 1 October 1987
    • journal article
    • research article
    • Vol. 28  (10) , 1620-1624
Abstract
The radiopharmaceutical, metaiodobenzylguanidine (MIBG) acts as an analog of norepinephrine (NE). Experiments in rats were carried out to determine how closely the movements of [125I]MIBG in the heart mimicked those of [3H]NE, and if the changes [125I]MIBG concentrations would reflect injury to, and function of, adrenergic neurons in the heart. Injury to adrenergic neurons by 6-hydroxydopamine substantially reduced the uptake of [125I]MIBG into the left ventricle, but the effect was less than that on uptake of [3H]NE uptake and concentration of endogenous NE. Similarly, when desmethylimipramine was given to inhibit the uptake-1 pathway of neurons, the reduction in uptake of [125I]MIBG was statistically significant but less than that of [3H]NE; part of this difference may be attributable to partial uptake of [125I]MIBG into neurons by a diffusion pathway. Substantial fractions of [125I]MIBG and [3H]NE were displaced from the heart by the sympathomimetic drug, phenylpropanolamine. When adrenergic neurons of the heart were stimulated by feeding of rats, the disappearance rates of [3H]NE and [125I]MIBG from the heart were significantly increased. Although not a perfect analog of [3H]NE, [125I]MIBG appears to enter and leave the heart in patterns similar to those of [3H]NE. Thus, movements of [125I]MIBG give indices of adrenergic neuron injury and function in the heart.