5-HT1 receptor binding sites in the guinea pig superior colliculus are predominantly of the 5-HT1D class and are presynaptically located on primary retinal afferents.
The superficial layers of the guinea pig superior colliculus are characterized by high densities of [3H]5-HT binding sites. We have chosen receptor autoradiography to establish the drug binding profile and the localization of these sites. The binding of [3H]5-HT to guinea pig superior colliculus was nearly completely blocked by drugs such as 5-carboxamido-tryptamine and yohimbine, but only slightly sensitive to the 5-HT1 receptor agonist 8-hydroxy-dipropylamino-tetralin. 5-HT1C antagonists such as mesulergine or the beta-adrenergic receptor blocking compound SDZ 21-009 did not show any effect. The profile of the majority of these sites corresponds to that of 5-HT1D sites. Unilateral enucleation resulted in a nearly complete depletion of [3H]5-HT binding in the contralateral superior colliculus, whereas [125I]Bolton-Hunter-8-methoxy-N-propylaminotetralin binding sites, corresponding to 5-HT1A receptors, were preserved. These results indicate that 5-HT1D (and not 5-HT1A) receptors might be presynaptically localized on non-serotoninergic neuronal pathways. The guinea pig visual system may be a useful model for the study of the properties of these presynaptic 5-HT heteroreceptors.
Waeber
C
C
Preclinical Research, Sandoz Pharma Ltd., Basel, Switzerland.
Palacios
J M
JM
D000344:Afferent Pathways / Q000737:chemistry; D000818:Animals; D006168:Guinea Pigs; D008297:Male; D011985:Receptors, Serotonin / Q000032:analysis* / Q000145:classification; D012160:Retina / Q000737:chemistry*; D013477:Superior Colliculi / Q000737:chemistry*
D011985:Receptors, Serotonin