Identification of 5HT2-receptors on longitudinal muscle of the Guinea pig ileum

Abstract

In binding experiments with the radioligands [3H]Ketanserin (HKet) and [125I]LSD (ILSD) 21 compounds were investigated using rat brain cortex membranes. The pKD-values of the compounds were virtually independent of the radioligand used and their rank order was consistent with classification of the binding sites as being of the 5-HT2-type. In contrast, in the longitudinal muscle of the guinea pig ileum in the presence of 0.3 μM cinanserin, ILSD labelled sites which were quite different to those in the cortex. In a functional test antagonism of the 5HT induced contraction of the guinea-pig ileum was measured in the presence of 1 μM atropine. The pharmacological inhibition constants (IC50-value..