Labelling with [125I]-SB 207710 of a small 5-HT4 receptor population in piglet right atrium: functional relevance.
1. We investigated the affinity of SB 207710 for sinoatrial 5-HT4 receptors and the density of right atrial 5-HT4 receptors with [125I]-SB 207710 in right atria of new-born piglets. 2. SB 207710 (1-100 nM) antagonized the 5-HT-evoked tachycardia surmountably with a pKB of 9.8. 3. [125I]-SB 207710 (5-1500 pM) labelled a small population of saturable binding sites with a pKD of 10.1 and with 5-HT4 receptor characteristics. The density of atrial binding sites with 5-HT4 receptor characteristics was 174 and 22 times lower respectively than those of atrial beta 1- and beta 2-adrenoceptors, labelled with (-)-[125I]-cyanopindolol. 4. We suggest that the small 5-HT4 receptor population may in part explain why the maximal tachycardia caused by 5-HT is smaller than that caused by catecholamines.
Kaumann
A J
AJ
Human Pharmacology Laboratory, Babraham Institute, Cambridge.
Lynham
J A
JA
Brown
A M
AM
D000818:Animals; D000831:Animals, Newborn; D016280:Atrial Function, Right / Q000187:drug effects*; D001667:Binding, Competitive; D004146:Dioxanes / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005260:Female; D008297:Male; D010880:Piperidines / Q000494:pharmacology*; D011985:Receptors, Serotonin / Q000145:classification / Q000187:drug effects* / Q000502:physiology*; D012701:Serotonin / Q000494:pharmacology; D012702:Serotonin Antagonists / Q000494:pharmacology*; D013552:Swine; D013610:Tachycardia / Q000139:chemically induced
D004146:Dioxanes; D010880:Piperidines; D011985:Receptors, Serotonin; C088873:SB 207710; D012702:Serotonin Antagonists; D012701:Serotonin