The architecture and musculotopic organization of the facial motor nucleus in the Cebus apella monkey (a New World primate) were investigated using histological techniques and a multiple labelling strategy, in which horseradish peroxidase-conjugated neuroanatomical tracers (CTB-HRP and WGA-HRP) and fluorescent tracers were injected into individual facial muscles. The facial motor nucleus was formed by multipolar motoneurons and had an ovoid shape, with its rostrocaudal axis measuring on average 1875 µ m. We divided the nucleus into four different subnuclei: medial, intermediate, dorsal and lateral. Retrograde labelling patterns revealed that individual muscles were innervated by longitudinal functional columns of motoneurons. The columns of the orbicularis oculi, zygomaticus, orbicularis oris, auricularis superior, buccinator and platysma muscles were located in the dorsal, intermediate, lateral, medial, lateral and intermediate subnuclei, respectively. However, the motoneuron columns of the levator labii superioris alaeque nasi muscle and frontalis muscle could not be associated with a specific subnucleus. The present results confirm previous studies regarding the musculotopic organization of the facial motor nucleus. However, we observed some particularities in terms of the relative size of each column in C. apella , which might be related to the functional and behavioral importance of each muscle in the particular context of this primate.

The morphology of the dura mater and its relationship with the structures of the cavernous sinus were analyzed in five tufted capuchin monkeys (Cebus apella) using histological sections, showing that the walls of the cavernous sinus of this species are similar to those of other primates, including man. Except for the medial wall of the cavernous sinus, the remaining walls consist of two distinct dura mater layers. The deep layer of the lateral wall of the cavernous sinus is contiguous to the sheath of the oculomotor, trochlear and ophthalmic nerves. Arterioles, venules, venous spaces, neuronal bodies and nervous fiber bundles are found on this lateral wall.

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-The cells of the choroid plexus of the lateral ventricles of the monkey Cebus apella apella were examined through scanning electron microscopy at contributing to the description of such structures in primates. The animals were anesthetized previously with 3% hypnol intraperitoneally and after perfusion with 2.5% glutaraldehyde, samples of the choroid plexus were collected after exhibition of the central portion and inferior horn of the lateral ventricles. The ventricular surface of those cells presents globose form as well as fine interlaced protrusions named microvilli. Among those, it is observed the presence of some cilia. Resting on the choroid epithelial cells there is a variable number of free cells, with fine prolongations which extend from them. They are probably macrophages and have been compared to Kolmer cells or epiplexus cells, located on choroid epithelium. The choroid plexus of the encephalic lateral ventricles of the monkey Cebus apella apella at scanning electron microscopy is similar to that of other primates, as well as to that of other species of mammals mainly cats and rats, and also humans.KEY WORDS: choroid plexus, monkey, scanning electron microscopy.Estudo do plexo coróide no macaco (Cebus apella apella) ao microscópio eletrônico de varredura RESUMO -As células do plexo coróide dos ventrículos laterais do macaco-prego (Cebus apella apella) foram examinadas ao microscópio eletrônico de varredura com o objetivo de melhor descrever e comparar este órgão ao de outras espécies de mamíferos, principalmente o homem. Inicialmente, os animais foram previamente anestesiados com hipnol a 3% intraperitonealmente e após perfusão com glutaraldeído 2,5%, amostras dos plexos coróides foram coletadas após exibição da porção central e corno inferior dos ventrículos laterais. A superfície ventricular dessas células apresenta forma globosa e a presença de finas protrusões entrelaçadas denominadas microvilosidades. Entre estas, observam-se alguns cílios. Repousando sobre as células epiteliais coróides está presente um número variável de células livres com finos prolongamentos que delas se estendem. São provavelmente macrófagos e têm sido comparadas com as células de Kolmer ou do epiplexo, localizadas sobre o epitélio coróide. O plexo coróide dos ventrículos encefálicos laterais do macaco Cebus apella apella ao microscópio eletrônico de varredura é similar ao de outros primatas, assim como de outras espécies de mamíferos, principalmente gatos e ratos, e também de humanos. PALAVRAS-CHAVE: plexo coróide, macaco, microscópio eletrônico de varredura.The discovery of the choroid plexus of the encephalic ventricles was attributed by Galeno to Herophilus (335-280 a.C.) who named them "chorioid menix". Rufos of Ephesus suggested the term "chorioid tunic" to describe the ependyma as the choroid plexus 1 . Later, the choroid plexus was studied at light and electron microscope levels in different animals and by several authors [2][3][4][5][6][7][8][9][10][11][12][13] .