NIMH DIRP MIB - Recent Findings

Background. The neurotransmitter substance P binds to the neurokinin-1 (NK1) receptor. We performed the first studies in the USA to image NK1 receptors and used the ligand [¹⁸F]SPA-RQ (substance P antagonist receptor quantifier). As with the initial use of most PET radiotracers, we must measure the distribution of radioactivity in the body over time to estimate the radiation exposure to organs of the body. These images show the distribution of radioactivity in the body over time after injection of [¹⁸F]SPA-RQ.

We subsequently performed a reproducibility study of kinetic brain imaging with [¹⁸F]SPA-RQ in human subjects. (see reference below). We are now studying this tracer in patients with panic disorder, before and after we induce a panic attack with a respiratory stimulant drug.

Legend. An example of a series of compressed whole-body planar PET images for a single healthy subject. The images were obtained 2, 20, 100 and 240 min after intravenous injection of 5.2 ± 0.2 mCi of [¹⁸F]SPA-RQ. All four decay-corrected images used the same color scale (bottom of figure).

References. 1.) D.R. Sprague, F. Chin, J.-S. Liow, M. Fujita, H.D. Burns, R. Hargreaves, J.B. Stubbs, V.W. Pike, R.B. Innis, and P.D. Mozley. Human biodistribution and radiation dosimetry of the tachykinin NK1 antagonist radioligand [¹⁸F]SPA-RQ: Comparison of thin-slice, bisected, and 2-D planar image analysis. J. Nucl. Med. 48: 100-107, 2007
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2) F. Yasuno., S.M. Sanabria, H.D. Burns, R.J. Hargreaves, S. Ghose, F.T. Chin, C.L. Morse, J. Hong, V.W. Pike, and R.B. Innis. PET imaging of neurokinin-1 (NK1) receptors with [¹⁸F]SPA-RQ in human subjects: Assessment of reference tissue models and their test-retest reproducibility. Synapse. 61: 242-251, 2007. Download Reference in PDF Format (284 kb)

3) Y. Fujimura, F. Yasuno, A. Farris, J.-S. Liow, M. Geraci, W. Drevets, D.S. Pine, S. Ghose, A. Lerner, R. Hargreaves, H.D. Burns, C. Morse, V.W. Pike, and R.B. Innis. Decreased neurokinin₁ (substance P) receptor binding in patients with panic disorder: positron emission tomographic study with [¹⁸F]SPA-RQ. Biol. Psychiatry, In Press. Download Reference