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The Inhibitory Effects Of Opioids On Voltage-Gated Calcium Influx In Neonatal Rat Carotid Body Type I Cells, Ellen M. Ricker
The Inhibitory Effects Of Opioids On Voltage-Gated Calcium Influx In Neonatal Rat Carotid Body Type I Cells, Ellen M. Ricker
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It is known that opioids inhibit the hypoxic ventilatory response, but little is known about the mechanisms that underpin this. This study's objectives were to examine which opioid receptors are located on the oxygen-sensing carotid body type I cells and determine whether selective agonists inhibit cellular excitability.
Immunocytochemistry revealed the presence of μ and κ opioid receptors on type I cells. The μ-selective agonist DAMGO (10μM) and the κ-selective agonist U50-488 (10μM) significantly (p<0.0025 and p<0.0095 respectively, unpaired student's t-test) inhibited high K+ induced rises in intracellular Ca2+ compared with controls. After a three-hour incubation with pertussis toxin, a Gi protein-coupled inhibitor, DAMGO and U50-488 (10μM) has no significant effect on the responses to K+.
These results indicate that opioids acting at μ and κ receptors inhibit voltage-gated Ca2+ influx in carotid body type I cells. This mechanism may explain, in …