CALRETININ-IMMUNOREACTIVE NEURONS IN PRIMATE PEDUNCULOPONTINE AND LATERODORSAL TEGMENTAL NUCLEI

Single- and double-antigen localization procedures were used to study the distribution, morphological characteristics and chemical phenotype of neurons containing the calcium-binding protein calretinin in the p edunculopontine and lalerodorsal tegmental nuclei of the cynomolgus mo nkey (Macaca fascicularis). Calretinin was detected in neurons that be longed to a highly heteromorphic and widely distributed subpopulation of the pedunculopontine and laterodorsal tegmental nuclei in the cynom olgus monkey. Double-immunostaining experiments revealed that about 12 % of these calretinin-containing neurons displayed immunoreactivity fo r another calcium-binding protein, Calbindin-D-28k. The calretinin/Cal bindin-D-28k double-labeled neurons had small to medium-sized perikary a, from which emerged a bipolar or multipolar dendritic arborization. Calretinin was also present in approximately 8% of the cholinergic neu rons of the pedunculopontine/laterodorsal nuclear complex, as visualiz ed on single sections immunostained for both calretinin and choline ac etyltransferase. These calretinin/choline acetyltransferase double-lab eled neurons displayed markedly different sizes and shapes, and occurr ed preferentially in the pars compacta and dissipata of the pedunculop ontine tegmental nucleus. Numerous calretinin-immunoreactive fibers we re also present within and around the superior cerebellar peduncle. So me of these varicose fibers closely surrounded large non-immunoreactiv e neurons; as well as large neurons staining positively for choline ac etyltransferase. This study provides the first evidence for the existe nce of calretinin-immunoreactive neurons within the primate pedunculop ontine and laterodorsal tegmental nuclei. Our data suggest that calret inin may play a role in the function of the pedunculopontine/laterodor sal nuclear complex by acting either alone or in conjunction with acet ylcholine or Calbindin-D-28k. (C) 1998 IBRO. Published by Elsevier Sci ence Ltd.