In rat brain, imidazoline I2 receptors are located on the mitochondrial outer membrane and their distribution correlates well with the enzyme MAO-B. Morevover, it has been found that chronic clorgyline administration results in a downregulation I2 binding sites in rat brain cortex. Although these findings suggest some relationship between the enzyme MAO and the I2 site, a direct interaction of imidazoline ligands with the active centre of MAO-A/B has been discounted.
Since clorgyline has a high affinity for the I2 site and moclobemide does not demonstrate any affinity for this site, it is possible that clorgyline's blockade of locomotor sensitization to quinpirole may be attributed to an action at this site. Therefore, if chronic clorgyline adminstration blocks quinpirole-induced locomotor sensitization via an activity at the I2 site, then it would be expected that chronic treatment with the I2 receptor ligand 2-BFI would also block locomotor sensitization to quinpirole.
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