Medicine and Health Sciences Commons^™

The Inhibitory Effects Of Opioids On Voltage-Gated Calcium Influx In Neonatal Rat Carotid Body Type I Cells, Ellen M. Ricker

Browse all Theses and Dissertations

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 …

Presynaptic Regulation Of Carotid Body Type I Cells By Histaminergic And Muscarinic Receptors, Carrie Marie Thompson

Browse all Theses and Dissertations

Type I cells are one of two main cell types located within the carotid body. These cells respond to hypoxia, hypercapnia, and acidosis by releasing excitatory and inhibitory neurotransmitters. This causes increased firing of the carotid sinus nerve and restores blood gas levels to their physiological values. While previous studies have shown whether individual neurotransmitters are excitatory or inhibitory, this work demonstrates how the interplay between two neurotransmitters may potentially shape the output of the carotid body. Histamine, which has previously been shown to have no effect on intracellular Ca2+ in type I cells, may function to modulate the actions …

The Presynaptic Regulation Of Isolated Neonatal Rat Carotid Body Type I Cells By Histamine, Drew C. Burlon

Browse all Theses and Dissertations

It has been previously shown that Carotid Body Type I cells have the ability to synthesize, package and release histamine in response to hypoxia, thereby contributing to the modulation of respiration within the rat. Here, isolated neonatal rat carotid body type I cells were used to identify the presynaptic effects of histamine and the specific receptor subtypes that modulate them. Although all four histamine receptor subtypes are expressed on the type I cells, and preliminary data showed promising results, further data proved that the activation of these receptors with histamine or selective agonists caused no rise in intracellular calcium ([Ca2+]i) …