title: Age-related changes in neurochemical components and retinal projections of rat intergeniculate leaflet.
abstract: Aging leads to several anatomical and functional deficits in circadian timing system. In previous works, we observed morphological alterations with age in hypothalamic suprachiasmatic nuclei, one central component of this system. However, there are few data regarding aging effects on other central components of this system, such as thalamic intergeniculate leaflet (IGL). In this context, we studied possible age-related alterations in neurochemical components and retinal projections of rat IGL. For this goal, young (3 months), adult (13 months), and aged (23 months) Wistar rats were submitted to an intraocular injection of neural tracer, cholera toxin subunit b (CTb), 5 days before a tissue fixation process by paraformaldehyde perfusion. Optical density measurements and cell count were performed at digital pictures of brain tissue slices processed by immunostaining for glutamic acid decarboxylase (GAD), enkephalin (ENK), neuropeptide Y (NPY) and CTb, characteristic markers of IGL and its retinal terminals. We found a significant age-related loss in NPY immunoreactive neurons, but not in immunoreactivity to GAD and ENK. We also found a decline of retinal projections to IGL with age. We conclude aging impairs both a photic environmental clue afferent to IGL and a neurochemical expression which has an important modulatory circadian function, providing strong anatomical correlates to functional deficits of the aged biological clock.
authors.affiliation: Laboratory of Neurochemical Studies, Federal University of Rio Grande do Norte, Natal, RN, Brazil.
authors.forename: Felipe P
authors.initials: FP
authors.lastname: Fiuza
authors.affiliation: Laboratory of Neurochemical Studies, Federal University of Rio Grande do Norte, Natal, RN, Brazil.
authors.forename: Kayo D A
authors.initials: KD
authors.lastname: Silva
authors.affiliation: Laboratory of Neurochemical Studies, Federal University of Rio Grande do Norte, Natal, RN, Brazil.
authors.forename: Renata A
authors.initials: RA
authors.lastname: Pessoa
authors.affiliation: Laboratory of Neurochemical Studies, Federal University of Rio Grande do Norte, Natal, RN, Brazil.
authors.forename: André L B
authors.initials: AL
authors.lastname: Pontes
authors.affiliation: Laboratory of Neurochemical Studies, Federal University of Rio Grande do Norte, Natal, RN, Brazil.
authors.forename: Rodolfo L P
authors.initials: RL
authors.lastname: Cavalcanti
authors.affiliation: Neuroscience Center, University of São Paulo City, São Paulo, SP, Brazil.
authors.forename: Raquel S
authors.initials: RS
authors.lastname: Pires
authors.affiliation: Laboratory of Neuroanatomy, Federal University of Rio Grande do Norte, Natal, RN, Brazil.
authors.forename: Joacil G
authors.initials: JG
authors.lastname: Soares
authors.affiliation: Laboratory of Neuroanatomy, Federal University of Rio Grande do Norte, Natal, RN, Brazil.
authors.forename: Expedito S
authors.initials: ES
authors.lastname: Nascimento Júnior
authors.affiliation: Laboratory of Neuroanatomy, Federal University of Rio Grande do Norte, Natal, RN, Brazil.
authors.forename: Miriam S M O
authors.initials: MS
authors.lastname: Costa
authors.affiliation: Laboratory of Neurochemical Studies, Federal University of Rio Grande do Norte, Natal, RN, Brazil.
authors.forename: Rovena C G J
authors.initials: RC
authors.lastname: Engelberth
authors.affiliation: Laboratory of Neurochemical Studies, Federal University of Rio Grande do Norte, Natal, RN, Brazil. jefsc@uol.com.br.
authors.forename: Jeferson S
authors.initials: JS
authors.lastname: Cavalcante
mesh_terms: D000375:Aging / Q000378:metabolism*; D000818:Animals; D002940:Circadian Rhythm; D007031:Hypothalamus / Q000737:chemistry* / Q000166:cytology; D007150:Immunohistochemistry; D008297:Male; D009474:Neurons / Q000166:cytology / Q000378:metabolism; D009478:Neuropeptide Y / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D012160:Retina / Q000737:chemistry* / Q000166:cytology; D013493:Suprachiasmatic Nucleus / Q000737:chemistry* / Q000166:cytology
chemical_list: D009478:Neuropeptide Y
keywords: Aging; Cholera toxin subunit b; Circadian timing system; Immunohistochemistry; Intergeniculate leaflet; Retinal projections