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Depressed ventilatory reflexes after capsaicin challenge in streptozotocin-treated rats
Dale R Bergren1, Marc S Rendell
1Department of Biomedical Sciences, School of Medicine Creighton University, 2500 California Plaza, Omaha, NE 68178, USA. dbergren@creighton.edu
Abstract:
Diabetic sensory neuropathy is an affliction that decreases sensory perception in a number of organ systems. Although little is known of its pulmonary effects certain diabetic patients have reduced airway reactivity to cold air and elevated cough threshold to irritant inhalation, reflexes reported to be mediated by pulmonary C-fibers. Therefore we studied the effects the selective C-fiber activator capsaicin (0.01% aerosol, 30 s) on variables of ventilation using a whole-body plethysmograph in age-matched rats treated with streptozotocin (STZ) or its vehicle at 6 and 12 weeks after treatment. Body weight increased and plasma glucose and glycosylated hemoglobin were stable in vehicle-treated rats. In STZ-treated rats body weight decreased and plasma glucose and glycosylated hemoglobin increased. Capsaicin challenge decreased tidal volume, respiratory rate and therefore minute ventilation in non-treated and vehicle-treated rats. However capsaicin challenge increased tidal volume thereby altering minute ventilation in STZ-treated rats. Specific airway resistance increased in both groups after capsaicin challenge. Changes in ventilation in response to capsaicin challenge in STZ-treated rats may involve C-fiber sensory neuropathy.
Insights
Diabetic sensory neuropathy may alter lung function. In diabetic rats, capsaicin (a C-fiber activator) increased tidal volume, unlike in healthy rats, suggesting C-fiber neuropathy impacts respiratory reflexes.
Area of Science:
- Physiology
- Neurology
- Pulmonology
Background:
- Diabetic sensory neuropathy affects multiple organ systems, potentially impacting pulmonary sensory pathways.
- Pulmonary C-fibers mediate reflexes like airway reactivity to cold air and cough.
- The effects of diabetic neuropathy on pulmonary C-fiber function remain largely unknown.
Purpose of the Study:
- To investigate the effects of diabetic sensory neuropathy on pulmonary C-fiber function.
- To assess changes in respiratory variables in response to capsaicin challenge in diabetic rats.
Main Methods:
- Streptozotocin (STZ)-induced diabetes model in rats.
- Assessment of ventilation variables using whole-body plethysmography.
- Administration of capsaicin aerosol to activate C-fibers.
Main Results:
- STZ-treated rats exhibited characteristic diabetic changes (decreased body weight, increased glucose and HbA1c).
- Capsaicin decreased tidal volume, respiratory rate, and minute ventilation in control rats.
- Capsaicin increased tidal volume and altered minute ventilation in STZ-treated rats.
- Specific airway resistance increased in both groups post-capsaicin.
Conclusions:
- Diabetic sensory neuropathy may alter pulmonary C-fiber-mediated ventilatory responses.
- These findings suggest a potential role for C-fiber neuropathy in respiratory dysfunction in diabetes.
