Differential distribution of 5-HT1A and 5-HT1B -like immunoreactivities in rat central nucleus of the amygdala neurones projecting to the caudal dorsomedial medulla oblongata

• Published in: Brain research 2010-05, Vol.1330, p.20-30
• Main Authors: Saha, Sikha, Gamboa-Esteves, Filomena O, Batten, Trevor F.C
• Format: Article
• Language: English
• Subjects: Biological and medical sciences; Central nervous system; Central neurotransmission. Neuromudulation. Pathways and receptors; Fundamental and applied biological sciences. Psychology; Neurology; Vertebrates: nervous system and sense organs
• ISSN: 0006-8993; 1872-6240
• DOI: 10.1016/j.brainres.2010.03.009

Abstract Neurones in the central nucleus of the amygdala (CeA) projecting to the caudal dorsomedial medulla oblongata play a key role in the autonomic expression of emotional behaviour. We have earlier shown that these projections from the CeA contain γ-aminobutyric acid. The CeA receives a dense serotonergic innervation from the raphé nuclei and expresses several serotonin (5-hydroxytryptamine, 5-HT) receptor subtypes, including the 5-HT1A and 5-HT1B subtypes. However, there have been no reports on the cellular distribution of these receptors in CeA projection neurones. This study was therefore designed to investigate the localisation of 5-HT1A and 5-HT1B receptors in CeA projection neurones identified by microinjection of a retrograde tracer, cholera toxin B-subunit (CTb) into the caudal dorsomedial medulla, targeting projections to the nucleus of the solitary tract. A large proportion (approximately 60%) of amygdala neurones retrogradely-labelled with CTb expressed 5-HT1B receptor-like immunoreactivity, whereas fewer (approximately 30%) expressed 5-HT1A receptor-like immunoreactivity. The retrogradely-labelled neurones positive for 5-HT1B receptor were present in both lateral and medial parts of the CeA whereas 5-HT1A receptor positive neurones were located mainly in the lateral part of the CeA. Since 5-HT plays an important role in controlling emotional behaviour and the 5-HT1A and 5-HT1B receptors have been shown to have distinct roles in the regulation of anxiety and depression, the differential expression of these receptors in CeA neurones projecting to the caudal dorsomedial medulla suggests that these projection neurones may act differentially in controlling autonomic expression of emotional behaviour.