Autoradiographic and SPECT imaging of cerebral opioid receptors with an iodine-123 labeled analogue of diprenorphine

Lever J., Ilgin N., Musachio J., Scheffel U., Finley P., Flesher J., ...Daha Fazla

SYNAPSE, cilt.29, sa.2, ss.172-182, 1998 (SCI-Expanded) identifier identifier identifier

  • Yayın Türü: Makale / Tam Makale
  • Cilt numarası: 29 Sayı: 2
  • Basım Tarihi: 1998
  • Dergi Adı: SYNAPSE
  • Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Sayfa Sayıları: ss.172-182
  • Anahtar Kelimeler: SPECT, opioid receptors, diprenorphine, autoradiography, mouse, POSITRON EMISSION TOMOGRAPHY, TEMPORAL-LOBE EPILEPSY, MU-OPIATE RECEPTORS, LIVING HUMAN-BRAIN, C-11 DIPRENORPHINE, N1'-(<C-11>METHYL) NALTRINDOLE, NORMAL VOLUNTEERS, INVIVO BINDING, HIGH-AFFINITY, QUANTIFICATION
  • Gazi Üniversitesi Adresli: Evet

Özet

The feasibility of imaging cerebral opioid receptors by single photon emission computed tomography (SPECT) has been established in baboon using a novel analog of diprenorphine (DPN) radiolabeled with iodine-123. The radioligand, [I-123]-O-IA-DPN (C6-O-[I-123]iodoallyl-DPN), was prepared in good yield (80%) with high radiochemical purity (>97%) and high specific radioactivity (>2,400 mCi/mu mol). In ex vivo autoradiographic studies, with and without naltrexone blockade, [I-I23]-O-IA-DPN specifically labeled opioid receptors throughout the mouse brain. Nonmetabolized radioligand accounted for >90% of the signal observed in extracts of whole mouse brain. SPECT imaging trials showed that [I-123]-O-IA-DPN selectively localized in regions of baboon brain known to have high densities of opioid receptors, such as striatum, thalamus, and temporal cortex. A much lower level of radioligand uptake and retention was noted for cerebellum, a region with few opioid binding sites. Pretreatment with naltrexone (6.5 mu mol/kg) blocked [I-I23]-O-IA-DPN binding in all brain regions. Using naltrexone blockade to define the nonspecific component for a given region of interest, total to nonspecific binding ratios increased linearly (r greater than or equal to 0.98) over the SPECT study with maximal values for striatum (9.8), thalamus (7.1), and temporal cortex (6.9) reached at the last time point investigated (3.5 h). Specific binding for these regions, assessed as the difference between regional SPECT activity for the control and blocked states, proved irreversible over the observation period. By the end of the time course, specific [I-123]-O-IA-DPN binding was >85% of total radioactivity in regions rich in opioid receptors and 62% of total radioactivity in cerebellum. The aggregate data are consistent with visualization of multiple opioid receptor types. Thus, [I-123]-O-IA-DPN should prove useful for SPECT studies within the constraints imposed by a lack of innate selectivity for a single type of brain opioid receptor. (C) 1998 Wiley-Liss, Inc.