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Saimiri Sciureus and Macaca Fascicularis): Parasagittal and Regional Organization Visualized by Lmmunohistochemistry

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Saimiri Sciureus and Macaca Fascicularis): Parasagittal and Regional Organization Visualized by Lmmunohistochemistry The Journal of Neuroscience, November 1988, @Ii): 4121-4137 Corticotropin-Releasing Factor in Olivocerebellar Climbing-Fiber System of Monkey (Saimiri sciureus and Macaca fascicularis): Parasagittal and Regional Organization Visualized by lmmunohistochemistry Choong I. Cha and Stephen L. Foote Department of Psychiatry, School of Medicine, University of California, San Diego, La Jolla, California 92093, and Research Institute of the Scripps Clinic, La Jolla, California 92037 An antiserum directed against the human form of cortico- within the uvula, the medial region of the dorsal parafloc- tropin-releasing factor (CRF) was utilized for immunohisto- culus, and the dorsal region of the pyramis, areas that re- chemical visualization of the distribution of this peptide in ceive their climbing fiber input primarily from the medial ac- the inferior olivary nucleus and cerebellum of 2 monkey cessory olive. Labeled fibers were much less dense and species (Saimiri sciureus, Macaca fascicularis). Colchicine were not clustered in the lateral hemispheres. pretreatment was not used. In both species, immunoreac- The present observation of CRF-like immunoreactivity in tivity was evident in the vast majority of neurons in the in- the monkey olivocerebellar pathway is compatible with the ferior olivary nucleus, with perikarya in the medial accessory previous observation of CRF mRNA within olivary neurons olive exhibiting especially intense staining. In cerebellum, of rat, baboon, and human (Young et al., 1988) and with no labeled perikarya were present, but immunoreactive ax- recent immunohistochemical findings in rat (Sakanaka et al., ons exhibiting the morphological characteristics of climbing 1987; Palkovits et al., 1987), cat (Cummings et al., 1988; fibers and their collaterals were observed in cortical and Kitahama et al., 1988), sheep (Cummings et al., 1988), and nuclear structures. In the cortex, most labeled axons were human (Powers et al., 1987). The present report thus rein- confined to the molecular and Purkinje cell layers. In the forces the suggestion that CRF is contained within the pri- sagittal plane, individual axonal arbors originated from thick, mate olivocerebellar pathway. Furthermore, it indicates that isolated axons at the base of the molecular layer and re- neurons in the medial accessory olive and their climbing fiber peatedly ramified as they extended toward the cortical sur- projections contain higher levels of CRF than neurons in face. In coronal sections, only thin, paired profiles were pres- other olivary subdivisions, producing parasagittally distrib- ent. Labeled processes also formed efflorescences in the uted and regionally specialized projections of these CRF- granular layer of cortex and were evident as highly arborized rich climbing fibers onto cerebellar cortex. axons in cerebellar nuclei. In each of these instances, the labeled elements resembled climbing fibers or their collat- Corticotropin-releasingfactor (CRF) is a 4 1-amino acid peptide erals as visualized by other methods. Other labeled pro- that is known to act as a hypothalamic releasingfactor, stim- cesses in the granular layer exhibited the morphological ulating the secretion of adrenocorticotropic hormone and beta- characteristics of mossy fiber axons. endorphin from the anterior pituitary (seeVale et al., 1983, for Immunoreactive, climbing-fiber-like axons were present in review). In addition, several lines of evidence (biochemical, the molecular layer throughout the major regions of cere- histochemical, and electrophysiological)indicate that CRF may bellar cortex. However, the most intensely labeled of these function as a neurotransmitter in extrahypophyseal neuronal axons were strikingly clustered within particular regions and pathways. For example, there have been several immunohis- parasagittal domains. In the vermis and intermediate zone, tochemical studies characterizing the anatomic distribution of intensely labeled axons were present only within parasag- CRF-like immunoreactivity (CRFLI) in rat brain (Bloom et al., ittal zones similar in location to those defined by climbing 1982; Merchenthaler et al., 1982; Olschowka, 1982;Cummings fiber innervation from the medial accessory olive. Intensely et al., 1983; Joseph and Knigge, 1983; Swansonet al., 1983; labeled axons were also densely but uniformly distributed Fellman et al., 1984; Merchenthaler, 1984; Skofitsch and Ja- cobowitz, 1985; Sakanakaet al., 1987). Thesereports have de- Received Sept. 21, 1987; revised Mar. 7, 1988; accepted Mar. 14, 1988. scribed extensive, widely distributed systemsof CRFLI in ex- During the course of this work, C. I. Cha was on leave from the School of trahypophyseal neuronal perikarya and fibers. However, limited Medicine, Seoul National University, Seoul, Korea. Antisera were generously information is available concerning the distribution of CRF in provided by W. Vale and J. Rivier of the Peptide Biology Laboratory of the Salk primate brain. For example, the only available anatomic ob- Institute. This research was supported by PHS Grant MH40008 and by grants from the Dystonia Medical Research Foundation and the MacArthur Foundation. servationsfrom monkeys, basedon immunohistochemicalstud- We wish to thank W. Chee for excellent technical assistance and J. H. Morrison ies, have been limited to examinations of hypothalamus (Ka- and F. E. Bloom. who urovided resources and consultation durina these studies. Correspondende should be addressed to Stephen L. Foote, Dep&tment of Psy- wata et al., 1982;Paul1 et al., 1984)and circumventricular organs chiatry (M-003), University of California, La Jolla, CA 92093. (Kawata et al., 1983). Also, with one exception describedbelow, Copyright 0 1988 Society for Neuroscience 0270-6474/88/l 14121-17$02.00/O similar limitations have applied to immunohistochemicalstud- 4122 Cha and Foote * LRF Climbing-Fiber System ies of human brain. Thus, we have undertaken a series of im- l-7 d. Frozen sections, 40 pm thick, were cut and incubated, freely munohistochemical studies in order to characterize the anatom- floating, for 48-72 hr in primary antiserum diluted 1:2000. The primary antiserum was visualized using avidin-biotin kits from Vector Labs ic distribution of extrahypophyseal CRFLI in brain stem areas (Burlingame, CA), which utilize as a secondary antiserum biotinylated of 2 species of monkey (Macaca fascicularis and Saimiri sci- anti-rabbit IgG that is subsequently bound to biotinylated HRP using ureus) (Cha and Foote, 1987; Foote et al., 1987; Foote and Cha, an avidin bridge. The sections were-developed for peroxidase reactivity 1988). An antiserum directed against the human form of CRF, with 3.3’-diaminobenzidine. The distribution of CRFLI was evaluated identical to the rat form (Vale et al., 198 1; Rivier et al., 1983; by careful comparison of the immunohistochemical sections with ad- jacent Nissl-stained sections. The nomenclatures of the atlases of Em- Shibihara et al., 1983) has been utilized to visualize CRFLI in mers and Akert (1963) for Saimiri and that of Kusama and Mabuchi neuronal perikarya and fibers. (1970) for Ma&a were used for brain-stem structures and that of Recently, certain observations have suggested that CRF is Madigan and Carpenter (197 1) for cerebellar structures. contained in neuronal perikarya in the inferior olive and in the The primary antiserum utilized in these studies was raised in rabbits and was directed against the rat/human form of CRF (Vale et al., 198 1; axons projecting from this nucleus into the cerebellum. These Rivier et al., 1983rShibihara et al., 1983). It was generously furnished axons constitute the olivocerebellar pathway which provides bv W. Vale and J. Rivier of the Salk Institute. In initial exneriments climbing-fiber input throughout cerebellar cortex, as well as t&zing antiseradirected against the ovine form of CRF, -immune- collateral innervation of deep cerebellar nuclei. In most early histochemical staining was found to be very weak. For the antiserum immunohistochemical studies, CRFLI was either not observed utilized in these studies (lot ~70). a dilution series of 1:lOOO. 1:2000. and 1:4000 was evaluated, and staining from the 1:2000 dilution was in the olivocerebellar system or only weak immunoreactivity found to be optimal. As controls for nonspecific immunoreactivity, a was evident (Merchenthaler et al., 1982, 1984; Cummings et sample of sections was reacted without primary antiserum, and a dif- al., 1983; Schipper et al., 1983). However, recent light-micro- ferent sample was exposed to 1:2000 primary antiserum that had been scopic observations in rat (Palkovits et al., 1987; Sakanaka et preadsorbed for 24 hr with human CRF (Penninsula Laboratories, Bel- mont, CA) at a concentration of 0.1 mg/ml (2.1 x 1O-5 M). Sections al., 1987) cat (Cummings et al., 1988; Kitahama et al., 1988), from these samples did not exhibit any of the immunoreactivity de- and sheep (Cummings et al., 1988) have demonstrated sub- scribed in this report. stantial CRFLI in inferior olive perikarya and in axons in cer- ebellum. This is compatible with reports of high levels of CRF in inferior olive as measured by radioimmunoassay (Palkovits Results et al., 1983, 1985) and with demonstrations of CRF mRNA in General observations these neurons by in situ hybridization in rat (Young et al., 1986; Immunoreactive neuronal perikarya and processeswere ob- Palkovits et al., 1987) baboon, and human (Young et al., 1986). served in numerous brain regions. Many similarities with pre- One electron-microscopic
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