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Published on: November 25, 2014
Opioid μ-receptors in the rostral medullary raphe modulate hypoxia-induced hyperpnea in unanesthetized rats
M B Dias1, T B Nucci, L G S Branco
1Department of Physiological Sciences, Federal University of Goias, Goiania, GO, Brazil.
Aim:
It has been suggested that the medullary raphe (MR) plays a key role in the physiological responses to hypoxia. As opioid μ-receptors have been found in the MR, we studied the putative role of opioid μ-receptors in the rostral MR (rMR) region on ventilation in normal and 7% hypoxic conditions.
Methods:
We measured pulmonary ventilation (VE) and the body temperatures (Tb) of male Wistar rats before and after the selective opioid μ-receptor antagonist CTAP (D-Phe-Cys-Tyr-D-Trp-Arg-Thr-Pen-Thr-NH2, cyclic, 0.1 μg per 0.1 μL) was microinjected into the rMR during normoxia or after 60 min of hypoxia.
Results:
The animals treated with intra-rMR CTAP exhibited an attenuation of the ventilatory response to hypoxia (430 ± 86 mL kg(-1) min(-1)) compared with the control group (790 ± 82 mL kg(-1) min(-1) ) (P < 0.05). No differences in the Tb were observed between groups during hypoxia.
Conclusion:
These data suggest that opioids acting on μ-receptors in the rMR exert an excitatory modulation of hyperventilation induced by hypoxia.
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