PT - JOURNAL ARTICLE AU - Martha I. Dávila-García AU - John L. Musachio AU - David C. Perry AU - Yingxian Xiao AU - Andrew Horti AU - Edythe D. London AU - Robert F. Dannals AU - Kenneth J. Kellar TI - [<sup>125</sup>I]IPH, an Epibatidine Analog, Binds with High Affinity to Neuronal Nicotinic Cholinergic Receptors DP - 1997 Jul 01 TA - Journal of Pharmacology and Experimental Therapeutics PG - 445--451 VI - 282 IP - 1 4099 - http://jpet.aspetjournals.org/content/282/1/445.short 4100 - http://jpet.aspetjournals.org/content/282/1/445.full SO - J Pharmacol Exp Ther1997 Jul 01; 282 AB - An analog of epibatidine (EB) was synthesized with an iodine atom in the 2 position of the pyridyl ring. This analog, (±)-exo-2-(2-iodo-5-pyridyl)-7-azabicyclo[2.2.1]heptane (IPH), as well as its two stereoisomers, displayed high affinity for neuronal nicotinic receptors; therefore, radioiodinated IPH, [125I]IPH, was synthesized with specific radioactivities consistently &gt;1000 Ci/mmol, and its properties as a radioligand for neuronal nicotinic receptors were evaluated. The characteristics of [125I]IPH binding in tissue homogenates appeared to be virtually identical to those reported for [3H]epibatidine binding; but the high specific radioactivity of [125I]IPH greatly facilitated measurements of nicotinic receptors in tissues with relatively low receptor densities and/or where tissues are in limited supply. Autoradiography with [125I]IPH provided clear localization of nicotinic receptors in brain and adrenal gland after film exposure times of ≤2 days. We conclude that [125I]IPH will be a very useful radioligand for the study of neuronal nicotinic receptors in brain and in peripheral ganglia. The American Society for Pharmacology and Experimental Therapeutics