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Khawaja XZ, Smith DL, Nawoschik SP, Zhang J, Dunlop J, Dilks DW, Olsen M, Schechter LE: WAY-100635 antagonist-induced plasticity of 5-HT receptors: regulatory differences between a stable cell line and an in vivo native system. J Neurochem. 2006 Jul;98(1):134-45.
We present evidence that the 5-hydroxytryptamine (1A) (5-HT (1A)) receptor antagonist, N-{2-[4-(2-methoxyphenyl)-1-piperazinyl]-ethyl}-N-(2-pyridinyl) cyclohexane carboxamide (WAY-100635), can induce receptor internalization in a human (h) 5-HT (1A) receptor Chinese hamster ovary (CHO-K1) cell system. Exposure of h5-HT (1A) CHO cells to WAY-100635 decreased the cell-surface h5-HT (1A) receptor density in a way that was both time (24-72 h) and concentration (1-100 nm) dependent.[(3) H] WAY-100635 and [(3) H] 8-hydroxy-dipropylaminotetralin ([(3) H] 8-OH-DPAT) saturation analyses demonstrated a significant reduction (50-60%) in total h5-HT (1A) receptor number in the WAY-100635-treated (100 nm; 72 h) compared with control cells. In WAY-100635-treated cells, the 8-OH-DPAT-mediated inhibition of forskolin (FSK)-stimulated cAMP accumulation was right-shifted and the maximal inhibitory response of 8-OH-DPAT was impaired compared with control cells. Similar results were obtained for 8-OH-DPAT-mediated Ca (2+) mobilization after WAY-100635 treatment. h5-HT (1A) receptors labeled with [(3) H] WAY-100635, as well as [(3) H] 4-(2'-Methoxy)-phenyl-1-[2'-(N-2''-pyridinyl)-p-fluorobenzamido] ethy l-piperazine (MPPF), exhibited a time-dependent rate of cellular internalization that was blocked by endocytotic suppressors and was pertussis-toxin insensitive. In contrast, quantitative autoradiographic studies demonstrated that chronic treatment of rats with WAY-100635 for two weeks produced a region-specific increase in the 5-HT (1A) receptor density. In conclusion, prolonged exposure of an h5-HT (1A) cell-based system to the 5-HT (1A) antagonist, WAY-100635, induced a paradoxical internalization of cell surface receptor resulting in depressed functional activity. This suggests that an antagonist can influence 5-HT (1A) receptor recycling in vitro differently to in vivo regulatory conditions. |
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