title: Coordinated autonomic and respiratory responses evoked by alerting stimuli: Role of the midbrain colliculi.
abstract: Threatening stimuli trigger rapid and coordinated behavioral responses supported by cardiorespiratory changes. The midbrain colliculi can generate coordinated orienting or defensive behavioral responses, and it has been proposed that collicular neurons also generate appropriate cardiovascular and respiratory responses to support such behaviors. We have shown previously that under conditions where collicular neurons are disinhibited, coordinated cardiovascular, somatomotor and respiratory responses can be evoked independently of the cortex by auditory, visual and somatosensory stimuli. Here we report that these natural stimuli effectively increase inspiratory time most likely though phase switching. As a result the pattern of phrenic and sympathetic coupling is an inspiratory-related sympathoexcitation. We propose that blockade of tonic GABAergic input in the midbrain colliculi permits alerting stimuli to drive command neurons that generate coordinated cardiovascular, respiratory and motor outputs. The outputs of these command neurons likely interact with the central respiratory pattern generator, however the precise output pathways mediating the coordinated autonomic and respiratory responses remain to be determined.
authors.affiliation: Australian School of Advanced Medicine, Macquarie University, NSW 2109, Australia; Departamento de Fisiologia e Biofísica, Universidade Federal de Minas Gerais (UFMG), Minas Gerais 31270-901, Brazil. Electronic address: flavinhacfmr@yahoo.com.br.
authors.forename: Flávia C F
authors.initials: FC
authors.lastname: Müller-Ribeiro
authors.affiliation: Australian School of Advanced Medicine, Macquarie University, NSW 2109, Australia.
authors.forename: Ann K
authors.initials: AK
authors.lastname: Goodchild
authors.affiliation: Australian School of Advanced Medicine, Macquarie University, NSW 2109, Australia.
authors.forename: Simon
authors.initials: S
authors.lastname: McMullan
authors.affiliation: Departamento de Fisiologia e Biofísica, Universidade Federal de Minas Gerais (UFMG), Minas Gerais 31270-901, Brazil.
authors.forename: Marco A P
authors.initials: MA
authors.lastname: Fontes
authors.affiliation: School of Medical Sciences (Physiology) and Bosch Institute, University of Sydney, NSW 2006, Australia.
authors.forename: Roger A L
authors.initials: RA
authors.lastname: Dampney
mesh_terms: D000818:Animals; D001341:Autonomic Nervous System / Q000502:physiology*; D063226:Central Pattern Generators / Q000502:physiology; D007245:Inferior Colliculi / Q000502:physiology*; D009474:Neurons / Q000502:physiology; D012119:Respiration; D012677:Sensation / Q000502:physiology*; D013477:Superior Colliculi / Q000502:physiology*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
chemical_list: D005680:gamma-Aminobutyric Acid
keywords: Alerting response; Command neuron; Inferior colliculus; Respiratory activity; Respiratory–sympathetic coupling; Superior colliculus