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An anterograde transport study of the descending projections of the central nucleus of the inferior colliculus
Author(s) -
Polson Jaimie W,
Bekric Lejla,
Garnsey Miles,
Dissanayake Hasthi,
Dampney Roger AL
Publication year - 2013
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.27.1_supplement.lb844
Subject(s) - rostral ventrolateral medulla , medulla oblongata , chemistry , brainstem , neuroscience , parabrachial nucleus , medulla , lateral parabrachial nucleus , pons , nucleus raphe magnus , anatomy , raphe nuclei , rostral ventromedial medulla , raphe , efferent , inferior colliculus , nucleus , dorsal raphe nucleus , central nervous system , biology , serotonin , nociception , serotonergic , afferent , hyperalgesia , biochemistry , receptor
The deep layers of the inferior (IC) and superior colliculus (SC) play a role in mediating escape behavior to a perceived threat (1). We recently showed that disinhibition of neurons in a discrete region of the IC and SC, centered on the central nucleus, evokes large synchronized bursts in renal sympathetic and phrenic nerve activity, as well as increases in blood pressure, heart rate and respiratory rate (2). However, the anatomical substrate underlying these responses is unclear. The purpose of this study, therefore, was to investigate the efferent projections of neurons in the IC with special reference to the cardiovascular and respiratory control sites of the medulla and pons. In anesthetized rats (ketamine, 100mg/kg; medetomidine 400μg/kg) 100nl of the anterograde tracer Dextran TMR (3000 MW) was injected stereotaxically into the central nucleus of the IC. After 5–7 days recovery, rats were anesthetized and perfused with 4% paraformaldehyde. Brainstem sections were examined under the fluorescent microscope for anterograde labeling. We found dense terminal labeling in the rostral ventromedial medulla (RVMM) and the medullary raphe, while there was sparse label in the rostral ventrolateral medulla (RVLM), parabrachial complex and A5 region. Labeling in the RVLM appeared to be dorsal to the presympathetic neurons. Our results indicate the cardiovascular responses from the IC may be mediated via a direct projection to medullary raphe and/or RVMM.