title: The mesencephalic GCt-ICo complex and tonic immobility in pigeons (Columba livia): a c-Fos study.
abstract: Tonic immobility (TI) is a response to a predator attack, or other inescapable danger, characterized by immobility, analgesia and unresponsiveness to external stimuli. In mammals, the periaqueductal gray (PAG) and deep tectal regions control the expression of TI as well as other defensive behaviors. In birds, little is known about the mesencephalic circuitry involved in the control of TI. Here, adult pigeons (both sex, n = 4/group), randomly assigned to non-handled, handled or TI groups, were killed 90 min after manipulations and the brains processed for detection of c-Fos immunoreactive cells (c-Fos-ir, marker for neural activity) in the mesencephalic central gray (GCt) and the adjacent nucleus intercollicularis (ICo). The NADPH-diaphorase staining delineated the boundaries of the sub nuclei in the ICo-GCt complex. Compared to non-handled, TI (but not handling) induced c-Fos-ir in NADPH-diaphorase-rich and -poor regions. After TI, the number of c-Fos-ir increased in the caudal and intermediate areas of the ICo (but not in the GCt), throughout the rostrocaudal axis of the dorsal stratum griseum periventriculare (SGPd) of the optic tectum and in the n. mesencephalicus lateralis pars dorsalis (MLd), which is part of the ascending auditory pathway. These data suggest that inescapable threatening stimuli such as TI may recruit neurons in discrete areas of ICo-GCt complex, deep tectal layer and in ascending auditory circuits that may control the expression of defensive behaviors in pigeons. Additionally, data indicate that the contiguous deep tectal SCPd (but not GCt) in birds may be functionally comparable to the mammalian dorsal PAG.
authors.affiliation: Department of Physiological Sciences, CCB, Federal University of Santa Catarina, Florianópolis, SC, 88040-900, Brazil. fmelleu@gmail.com.
authors.forename: Fernando Falkenburger
authors.initials: FF
authors.lastname: Melleu
authors.affiliation: Department of Physiological Sciences, CCB, Federal University of Santa Catarina, Florianópolis, SC, 88040-900, Brazil.
authors.forename: C
authors.initials: C
authors.lastname: Lino-de-Oliveira
authors.affiliation: Department of Physiological Sciences, CCB, Federal University of Santa Catarina, Florianópolis, SC, 88040-900, Brazil.|Institute of Biomedical Engineering, EEL-CTC, Federal University of Santa Catarina, Florianópolis, SC, 88040-900, Brazil.
authors.forename: J
authors.initials: J
authors.lastname: Marino-Neto
mesh_terms: D000818:Animals; D001931:Brain Mapping; D010856:Columbidae; D005260:Female; D046353:Immobility Response, Tonic / Q000502:physiology*; D008297:Male; D009252:NADPH Dehydrogenase / Q000378:metabolism; D009434:Neural Pathways / Q000502:physiology*; D009474:Neurons / Q000378:metabolism; D010487:Periaqueductal Gray / Q000166:cytology / Q000378:metabolism*; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism*; D018709:Statistics, Nonparametric; D013477:Superior Colliculi / Q000166:cytology / Q000378:metabolism*
chemical_list: D016760:Proto-Oncogene Proteins c-fos; D009252:NADPH Dehydrogenase
keywords: Avian brain; Defensive behavior; Periaqueductal gray; Tonic immobility; c-Fos