title: Disinhibition of the midbrain colliculi unmasks coordinated autonomic, respiratory, and somatomotor responses to auditory and visual stimuli.
abstract: The midbrain superior and inferior colliculi have critical roles in generating coordinated orienting or defensive behavioral responses to environmental stimuli, and it has been proposed that neurons within the colliculi can also generate appropriate cardiovascular and respiratory responses to support such behavioral responses. We have previously shown that activation of neurons within a circumscribed region in the deep layers of the superior colliculus and in the central and external nuclei of the inferior colliculus can evoke a response characterized by intense and highly synchronized bursts of renal sympathetic nerve activity and phrenic nerve activity. In this study, we tested the hypothesis that, under conditions in which collicular neurons are disinhibited, coordinated cardiovascular, somatomotor, and respiratory responses can be evoked by natural environmental stimuli. In response to natural auditory, visual, or somatosensory stimuli, powerful synchronized increases in sympathetic, respiratory, and somatomotor activity were generated following blockade of GABAA receptors in a specific region in the midbrain colliculi of anesthetized rats, but not under control conditions. Such responses still occurred after removal of most of the forebrain, including the amygdala and hypothalamus, indicating that the essential pathways mediating these coordinated responses were located within the brain stem. The temporal relationships between the different outputs suggest that they are driven by a common population of "command neurons" within the colliculi.
authors.affiliation: Australian School of Advanced Medicine, Macquarie University, New South Wales, Australia; and Laboratório de Hipertensão, Departamento de Fisiologia e Biofísica, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Minas Gerais, Brazil; and.
authors.forename: Flávia C F
authors.initials: FC
authors.lastname: Müller-Ribeiro
authors.affiliation: School of Medical Sciences (Physiology) and Bosch Institute, University of Sydney, New South Wales, Australia roger.dampney@sydney.edu.au.
authors.forename: Roger A L
authors.initials: RA
authors.lastname: Dampney
authors.affiliation: Australian School of Advanced Medicine, Macquarie University, New South Wales, Australia; and.
authors.forename: Simon
authors.initials: S
authors.lastname: McMullan
authors.affiliation: Laboratório de Hipertensão, Departamento de Fisiologia e Biofísica, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Minas Gerais, Brazil; and.
authors.forename: Marco A P
authors.initials: MA
authors.lastname: Fontes
authors.affiliation: Australian School of Advanced Medicine, Macquarie University, New South Wales, Australia; and.
authors.forename: Ann K
authors.initials: AK
authors.lastname: Goodchild
mesh_terms: D000161:Acoustic Stimulation; D000818:Animals; D001341:Autonomic Nervous System / Q000502:physiology*; D003655:Decerebrate State / Q000503:physiopathology*; D005072:Evoked Potentials, Auditory / Q000502:physiology; D005074:Evoked Potentials, Visual / Q000502:physiology; D007245:Inferior Colliculi / Q000187:drug effects / Q000503:physiopathology*; D008297:Male; D008845:Microinjections; D023421:Models, Animal; D009044:Motor Cortex / Q000502:physiology*; D010775:Photic Stimulation; D010852:Picrotoxin / Q000008:administration & dosage / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012143:Respiratory Physiological Phenomena; D013477:Superior Colliculi / Q000187:drug effects / Q000503:physiopathology*; D013997:Time Factors
chemical_list: D010852:Picrotoxin
keywords: arterial pressure; command neuron; defensive behavior; phrenic nerve activity; sympathetic activity