The presence of neuronal-specific nuclear protein (NeuN) in the circadian timing system of the capuchin monkey (Cebus apella)

Study carried out at Universidade Federal do Rio Grande do Norte � UFRN, Natal (RN), Brazil; Universidade de Sao Paulo � USP, Sao Paulo (SP), Brasil; Universidade Estadual Paulista “Julio de Mesquita Filho” � UNESP, Aracatuba (SP) Brazil. 1 Laboratorio de Cronobiologia, Centro de Biociencias, Universidade Federal do Rio Grande do Norte � UFRN, Natal (RN), Brazil. 2 Departamento de Anatomia da Universidade de Sao Paulo � USP, Sao Paulo (SP), Brazil. 3 Departamento de Ciencias Basicas da Universidade Estadual Paulista “Julio de Mesquita Filho” � UNESP, Aracatuba (SP) Brazil. Corresponding author: Jeferson de Sousa Cavalcante � Centro de Biociencias, Universidade Federal do Rio Grande do Norte � Caixa Postal 1511 � CEP 5�078-�70 � Natal (RN), Brazil � Phone: +55 (84) 3215-340� � Fax: +55 (84) 3211-�20� � E-mail: jefsc@uol.com.br Received: January 8, 2010; Accepted: March 28, 2010 ABSTRACT Background and objective: The circadian timing system (CTS) is composed of a group of specialized neuronal structures that establish a temporal organization of physiological and behavioral processes within precise patterns. The central components of this system are the suprachiasmatic nucleus of the hypothalamus (SCN) and the intergeniculate leaflet of the thalamus (IGL). The objective of this study was to verify the presence of the neuron-specific nuclear protein (NeuN) in the circadian timing system of capuchin monkeys (Cebus apella) using immunohistochemical techniques. Methods: Capuchin monkeys (Cebus apella) were anesthetized and transcardially perfused with 4% paraformaldehyde in 0.1 M phosphate buffer, and then their brains were removed and frozen. A microtome was used to make 30 μm sections in the coronal plane. One of the series was used for Nissl staining (thionin) to demarcate the cytoarchitecture, and the remainders of the sections were processed for immunohistochemical detection of NeuN (ABC protocol). Results: NeuN-positive neurons were observed in the suprachiasmatic nucleus of the capuchin monkey. The pregeniculate nucleus (PGN), a structure equivalent to the ventral lateral geniculate nucleus (vLGN) and to the IGL in rodents, did not have any NeuN-positive neurons. Conclusions: In this primate species, only the suprachiasmatic nucleus neurons of the central structures of the circadian timing system express the NeuN protein.