Correspondence between 5-HT2 receptors and serotonergic axons in rat neocortex.
The anatomic relationship between serotonergic (5-HT) axons and 5-HT2 receptors in the rat forebrain was determined by a combined analysis of transmitter immunocytochemistry and receptor autoradiography. High densities of 5-HT2 receptors, localized by the ligand N1-methyl-2-125I-LSD (125I-MIL), are found in neocortex and striatum; these regions also receive a dense serotonergic innervation. Regional variations in the density of 5-HT2 receptors and 5-HT axons correspond closely in most, but not all, areas of the forebrain. In somatosensory cortex (SI), the laminar distribution of 5-HT2 receptors closely matches that of 5-HT axons: in particular, a dense band of 5-HT2 receptors in layer Va of SI is in precise register with a dense plexus of fine 5-HT axons. We have also observed a close spatial relationship between 5-HT2 receptors and fine axons in other areas of the forebrain, suggesting that 5-HT2 receptors may be selectively linked to a particular type of 5-HT axon terminal. Since fine axons of this type have been reported to arise from the dorsal raphe nucleus, it appears likely that 5-HT2 receptors may mediate the effects of dorsal but not median raphe projections.
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Department of Neuroscience, Johns Hopkins Medical Institutions, Baltimore, MD 21205.
Yagaloff
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Mamounas
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Hartig
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Molliver
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D000818:Animals; D001345:Autoradiography; D001369:Axons / Q000032:analysis*; D002540:Cerebral Cortex / Q000032:analysis* / Q000166:cytology; D007150:Immunohistochemistry; D008238:Lysergic Acid Diethylamide / Q000031:analogs & derivatives / Q000378:metabolism; D008297:Male; D009044:Motor Cortex / Q000032:analysis / Q000166:cytology; D051381:Rats; D011919:Rats, Inbred Strains; D011985:Receptors, Serotonin / Q000032:analysis*; D012701:Serotonin / Q000032:analysis*; D013003:Somatosensory Cortex / Q000032:analysis / Q000166:cytology
D011985:Receptors, Serotonin; D012701:Serotonin; C048042:N(1)-methyl-2-lysergic acid diethylamide; D008238:Lysergic Acid Diethylamide