Figure 7.

Physiological consequences of 5-HT_1A:5-ht_5b co-expression. To test whether translocation of 5-HT_1A by 5-ht_5b effects cyclic adenosine monophosphate (cAMP) signaling, we measured the cellular cAMP level under various conditions. To measure the decrease of cAMP, 50 nM Forskolin was added to all cells before the start the experiment to increase cAMP levels. Mock-transfected cells treated with Forskolin and stimulated with 1 μM 5-HT served as control and were set to 100%. In all experiments, cells were transfected with an equimolar amount of DNA. To keep the amount of DNA the same in experiments with only one receptor, a filler plasmid was co-transfected. Expression of 5-ht_5b without stimulation with 5-HT decreased cAMP by −7.75% ± 1.012 (I), while addition of 5-HT did not enhance the reaction (−9.46% ± 1.296; II). Expressing 5-HT_1A in cells had no effect on cAMP levels without stimulation (−2.49% ± 1.366; III), but adding 5-HT decreased cAMP by −28.12% ± 1.096 (IV). Co-expression of 5-HT_1A and 5-ht_5b together without stimulation by 5-HT lead to a drop in cAMP by −10.37% ± 1.029 (V). Adding 5-HT to co-expressing cells dropped the cAMP level by −19.91% ± 2.219 (VI). Asterisks indicate significance (**p ≤ 0.01; ***p ≤ 0.001; one-way-ANOVA with Bonferroni’s post-test for multiple comparisons).