5-HT1A-receptors mediate stimulation of adenylate cyclase in rat hippocampus

Serotonin (5-HT) stimulated adenylate cyclase activity in homogenates of rat hippocampus. This effect was pharmacologically characterised with a series of agonists and antagonists of various structural classes. These compounds where also tested in radioligand binding studies using selective ligands for the various subtypes of 5-HT1 and 5-HT2 receptors. 5-HT1A, 5-HT1B and 5-HT1C recognition sites were labelled with [3H]8-OH-DPAT([3H]8-hydroxy-2-(di-n-propylamino)-tetralin) in pig cortex membranes, [125I]CYP([125I]iodocyanopindolol) in rat cortex and [3H]mesulergine in pig choroid plexus membranes, respectively. The rank order of potency of 13 agonists stimulating adenylate cyclase activity in homogenates of rat hippocampus was in good agreement with the rank order of affinity of these agonists for the 5-HT1A binding site: N,N-dipropyl-5-carboxamidotryptamine (DP-5-CT) greater than 5-carboxamidotryptamine (5-CT) greater than 8-OH-DPAT greater than 5-HT greater than 5-methoxytryptamine (5-OCH3T) greater than d-LSD greater than 5-methoxy-3-(1,2,3,6-tetrahydro-4-pyridinyl)-1H-indole (RU 24969) greater than alpha-methylserotonin (alpha-CH3-5-HT) greater than dopamine greater than 2-methylserotonin (2-CH3-5-HT). The correlation between the respective potencies and affinities of these agonists was r = 0.934, P less than 0.001. There was no correlation between stimulation of adenylate cyclase activity by these agonists and their affinity for 5-HT1B, 5-HT1C or 5-HT2 binding sites. r = 0.381-0.108, P less than 0.20-0.73.(ABSTRACT TRUNCATED AT 250 WORDS)