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Date of Award
Dissertation - Pacific Access Restricted
Doctor of Philosophy (Ph.D.)
Pharmaceutical and Chemical Sciences
First Committee Member
Second Committee Member
Third Committee Member
Fourth Committee Member
Purpose: 5-hydroxytryptamine (5-HT) is an important neurotransmitter in depression. It is believed that α 1 and α 2 adrenoceptors mediate the 5-HT level in the brain. The mechanism is complex and not well explored. Especially in different combination treatments, the receptor systems may show varied modulation capability. Additionally, some research has suggested that α 2 heteroceptors may contribute to the time delay problem in dual depression treatment which is thought as the time needed for certain inhibition receptor to get desensitized. We hypothesized that the α 2 adrenoceptors had inhibition effect on 5-HT level in dorsal raphé nucleus (DRN), Prefrontal cortex (PFC) and Hippocampus (HP) with the dual reuptake inhibition. The present study was undertaken to explore the effect of BRL44408 (α 2 receptor antagonist) on 5-HT level in rat PFC, DRN and HP under dual antidepressant with blocking the α 1 receptor. Method: Serotonin reuptake inhibitor and norepinephrine reuptake inhibitor were used to mimic the dual reuptake inhibition antidepressant. To differentiate the α 2 adrenoceptors effect from al adrenoceptors effect, prazosin, an antagonist of α 1 adrenoceptors, was added to block α 1 adrenoceptors. Using the microdialysis method, the drug combination was examined in HP area and then DRN area to explore the drug effect on time course of 5-HT release in DRN and PFC. Based on the experiment results from DRN and PFC, a mechanism-based pharmacodynamic model was developed. Result: BRL44408 increased the serotonin (5-HT) level in rat PFC, DRN and HP to different degrees with the dual reuptake inhibition (p < 0.05). The overall model reasonably captured the time course of 5-HT in both DRN and PFC with different dose schemes of BRL44408. The model predicted EC50 of BRL44408 (0.0075 µM) for the α 2 heteroreceptor which control PFC 5-HT is close to the reported value of BRL44408 for α 2 adrenorceptor (0.008 µM). However, the model predicted EC50 of BRL44408 on the α 2 heteroreceptor which control DRN 5-HT need to be explained. Simulation result from this model suggested varied modulation capability of α 2 adrenoceptors on the 5-HT in DRN and the 5-HT in PFC. Conclusion: α 2 heteroceptor play a role in regulation 5-HT level under dual reuptake inhibition. Further exploration may bring a potential target for depression treatment. The mechanism model was developed to characterize and better understand the neurotransmitter mechanisms, providing estimations of various parameters of the disease related receptor system.
Sun, Jingjing. (2012). Exploring the effect of alpha2 receptor on brain 5-HT via a mechanism-based pharmacodynamic model. University of the Pacific, Dissertation - Pacific Access Restricted. http://scholarlycommons.pacific.edu/uop_etds/154
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