Quantification of in vivo binding of [3H]RX 821002 in rat brain: evaluation as a radioligand for central alpha 2-adrenoceptors.


On the basis of its established in vitro characteristics, [3H]RX 821002 was evaluated in rats as an in vivo radioligand for central alpha 2-adrenoceptors. Estimates for in vivo binding potential, obtained by compartmental analyses of time-radioactivity data, ranged between 1.9 for hypothalamus and 0.2 for cerebellum, with a regional distribution in brain which was similar to that observed in vitro. Selectivity and specificity of the signal were checked by predosing with either the alpha 2-antagonists, idazoxan or yohimbine, the alpha 2-agonist, clonidine, or the alpha 1-antagonist, prazosin. Pretreatment of the rats with the selective neurotoxin, DSP-4, had no significant effect on [3H]RX 821002 binding, suggesting that the majority of labelled sites were situated post-junctionally. The studies indicate that [3H]RX 821002 can be used experimentally as an in vivo marker for central alpha 2-adrenoceptors. The size and rate of expression of the specific signal encourage the development and assessment of [11C]RX 821002 for clinical PET studies.


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@article{Hume1992QuantificationOI, title={Quantification of in vivo binding of [3H]RX 821002 in rat brain: evaluation as a radioligand for central alpha 2-adrenoceptors.}, author={S. P. Hume and Adriaan A. Lammertsma and Jolanta Opacka-Juffry and R. G. Ahier and Ralph Myers and Jill E. Cremer and Alan L. Hudson and David J. Nutt and Victor W. Pike}, journal={International journal of radiation applications and instrumentation. Part B, Nuclear medicine and biology}, year={1992}, volume={19 8}, pages={841-9} }