Preprodynorphin-, preproenkephalin-, preprotachykinin A- and preprotachykinin B-immunoreactive neurons in the accumbens nucleus and olfactory tubercle: Double-immunofluorescence analysis

Preprodynorphin (PPD), preproenkephalin (PPE) and preprotachykinins A (PPTA) and B (PPTB) are known to be expressed by neostriatal projection neurons. In the present study, we investigated the distributions and colocalizations Of immonoreactivities for those prepropeptides in the ventral striatum, Such as the accumbens nucleus (Acb) and olfactory tubercle (OT). Antibodies raised against C-terminal portions of the prepropeptides labeled cell bodies of neurons with diameters of 8-15 mum. PPD-, PPE- and PPTA-immunoreactive neurons were distributed throughout the Acb and concentrated in the dense cell layer of the OT. PPTB-immunoreactivc neurons were observed to form cell clusters, which were localized in p-opioid receptor-immunoreactive patchy regions in the Acb, but were very rarely found in the dense cell layer of the OT. Double-immunofluorescence analysis revealed that PPD, PPE and PPTB immunoreactivities were shown in 69%, 19% and 14% of PPTA-immunoreactive neurons, respectively, in the Acb core region, and in 92%, 7% and 25% of PPTA-immunoreactive neurons, respectively, in the Acb shell region. In the olfactory bulb, 51%, 19% and 3% of PPTA-immunoreactive neurons showed PPD, PPE and PPTB immunoreactivities, respectively. PPD and PPE immunoreactivities were rarely coexpressed in single neurons of all striatal regions. The present results indicated that, although PPTA and PPE were occasionally coexpressed in single neurons of the ventral striatum, the segregated expression of PPD and PPE in the ventral striatum was similar to that in the dorsal striatum. The clustered localization of PPTB-expressing neurons in the Acb and near absence of PPTB-expressing neurons in the dense cell layer of the OT suggests that neurokinin B is a key substance in differentiating between the ventral and dorsal striatal regions. (C) 2002 IBRO. Published by Elsevier Science Ltd. All rights reserved.