Role of PKC and ERK in Spontaneous Firing Activity of Locus Coeruleus in Mice
| Autor: | Chieh-Yi Wu, 吳杰義 |
|---|---|
| Rok vydání: | 2012 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 100 Locus coeruleus (LC) is one of the noradrenergic neurons, and involving many brain functions just like arousal, stress, circadian rhythm and antinociception. In electrophysiology, LC fires action potential spontaneously. This characteristic of spontaneous firing maybe involves in regulating the circadian rhythm. However, the spontaneous firing mechanism is still unknown. We want to know that what the signal input to the LC neurons and how the input to affect the spontaneous firing pattern of LC neurons. We speculate that the protein kinase C (PKC) / extracellular signal-regulated kinase (ERK) pathway, melatonin and GABABR are possibly involving in regulating spontaneous firing frequency of LC neurons. And this regulation may change the voltage-gated potassium channel conductance, one of crucial component in action potential. Increasing the potassium channel conductance would prolong the time between the action potentials and make the firing rate slow down. Or decreasing the potassium channel conductance would reduce the time between action potential intervals and makes the firing frequency speed up. First, we used the PKC activator, Phorbol 12,13-diacetate (PDA), to treat LC and see that how the spontaneous firing pattern changed. We found the spontaneous firing rate is slow down about 91% when treated the 3μM PDA. And this effect could be reverse by pretreat the PKC inhibitor, Ro-31-8220, which reducing the PDA effect about 60%. We also used the voltage-gated potassium channel blocker, 4-Aminopyridine (4-AP), to pretreat the slice just like PKC inhibitor to see the spontaneous firing rate changing by PDA. We found that 4-AP is also reducing PDA effect about 55%. Then, ERK is in the down-stream of PKC pathway, so the mechanism of control the spontaneous firing frequency may due to activate ERK via activating PKC. So we used ERK inhibitors, U0126 and PD98059, to pretreat LC, to see how to affect the PDA or not. But the slowed the effect of slowing spontaneous firing frequency by PDA is not affected. In the melatonin experiments, applying the melatonin receptor agonist, 6-chloromelatonin does not affect the spontaneous firing rate of LC neurons. In the GABABR experiments, applying the GABABR agonist would slow the spontaneous firing rate and the inhibitory effect could be reduced by ERK inhibitor. The results show that the spontaneous firing frequency of LC neurons is regulating by PKC and GABABR. Activation of PKC or GABABR would open the voltage-gated potassium channels and make the spontaneous firing frequency slowing down. In the PKC pathway, ERK is not involving in the pathway with regulating the spontaneous firing rate of LC neurons. But in the GABABR inducing the inhibitory effect in spontaneous firing, ERK play an important role in the pathway. Shows that at least two different pathway regulate the spontaneous firing of LC neurons. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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