Title: The role of the hypothalamic paraventricular nucleus (PVN) in mediating cardiorespiratory responses to activation of the suprachiasmatic nucleus (SCN)
Abstract:The SCN is responsible for controlling endogenous circadian rhythms. Respiratory drive is one of many biological parameters that may vary over a 24-h period. Previously, we demonstrated that activatio...The SCN is responsible for controlling endogenous circadian rhythms. Respiratory drive is one of many biological parameters that may vary over a 24-h period. Previously, we demonstrated that activation of the SCN stimulated cardiorespiratory responses. However, no abundant projections were observed from the SCN to the brainstem site involved in cardiorespiratory control. We hypothesize that stimulation of the SCN increases cardiorespiratory activity via neurons in the PVN. Male Sprague-Dawley rats were microinjected bilaterally in the PVN with neurotoxin ibotenic acid (50nl; 50μg/μl) or saline. After 10–14 days, rats in both groups were anesthetized, mechanically ventilated, and microinjected with 0.1M DL-homocysteic acid (DLH, 20 nL) into the SCN. In the saline control group, DLH stimulated peak diaphragm electromyographic activity by 33 ± 4 % (p<0.05), peak genioglossus electromyographic activity by 32 ± 8 % (p<0.05), and respiratory frequency by 19 ± 5 % (p<0.05). There was no significant change (p >0.05) in any of the measured respiratory parameters following unilateral injection of DLH into the SCN of rats treated with ibotenic acid. However, both blood pressure and heart rate were significantly (p <0.05) elevated in both groups in response to activation of the SCN. These data demonstrate that a physiologic pathway originating in the SCN and projecting through the PVN to the brainstem neurons influences respiratory drive. Supported by NIH Grants NS-45859, NINDS/NCRR U54-NS-39407, and HL-50527.Read More
Publication Year: 2007
Publication Date: 2007-01-01
Language: en
Type: article
Indexed In: ['crossref']
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