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Pharmacological Characterization of 5-Hydroxytryptamine Receptors in the Gastrointestinal Tract
Published in T.S. Gaginella, J.J. Galligan, SEROTONIN and GASTROINTESTINAL FUNCTION, 2020
Jeremy D. Gale, Keith T. Bunce
The most selective agents available for the blockade of 5-HT1A-mediated responses are SDZ 216–525 and WAY 100135. In radioligand binding experiments, SDZ 216–525 had an affinity (pKD) at 5-HT1A receptors of 9.2 and, in a functional bioassay, the compound antagonized the inhibitory effect of 8-OH-DPAT on adenylyl cyclase activity with a pKB of 10.34 SDZ 216–525 demonstrated 1000-fold selectivity for 5-HT1A receptors and 50–100-fold specificity for 5-HT1A over other receptor types. WAY 100135 is also a very selective compound, but is a weaker antagonist at 5-HT1A receptors than is SDZ 216–525. In a binding assay, WAY 100135 inhibited the binding of 3H-5-HT to rat hippocampal membranes with a pKi of 7.5.35 In guinea pig ileum, WAY 100135 antagonized the inhibitory effect of 5-HT with a pA2 of 7.2.36 The pharmacological profile of these compounds may vary depending upon the location of the 5-HT1A receptor under investigation. Many antagonists of postjunctional 5-HT1A receptors are partial agonists at prejunctional 5-HT1A receptors, as demonstrated for SDZ 216-525, but not for WAY 100135.37 This phenomenon is likely to result from a high reserve in the prejunctional receptor population or from an increased efficiency in receptor-effector coupling compared to that of postjunctional sites.
Pindolol potentiates the antidepressant effect of venlafaxine by inhibiting 5-HT1A receptor in DRN neurons of mice
Published in International Journal of Neuroscience, 2021
In in vivo extracellular electrophysiological studies, 5-HT delivered to the DRN region of rat by microiontophoresis caused a decrease in the number of firing in the neurons in this region and this effect was blocked by WAY 100635, 5-HT1A receptor antagonist [12,13,32]. Bayliss et al. (1997) demonstrated the presence of 5-HT1A receptors in the neurons of the caudal raphe nucleus by using WAY 100135 [33]. Similarly, in the current study, we showed that WAY100135 blocked the 5-HT effect on DRN neurons in Balb/c mice. WAY 100135 is a potent and specific antagonist of 5-HT1A receptors. This indicates that the presence of 5-HT in the DRN region results in activation of somatodendritic 5-HT1A receptors, which, in turn, inhibits the DRN neurons.