Synaptic connections between GABAergic elements and serotonergic terminals or projecting neurons in the ventrolateral orbital cortex.
The ventrolateral orbital cortex (VLO) is part of an endogenous analgesic system, consisting of the spinal cord-thalamic nucleus submedius-VLO periaqueductal gray (PAG)-spinal cord loop. The present study examined morphological connections of GABAergic (gamma-aminobutyric acidergic) neurons and serotonergic projection terminals from the dorsal raphe nucleus (DR), as well as the relationship between GABAergic terminals and VLO neurons projecting to the PAG, by using anterograde and retrograde tracing combined with immunofluorescence, immunohistochemistry, and electron microscopy methods. Results indicate that the majority (93%) of GABAergic neurons in the VLO also express the 5-HT(1A) (5-hydroxytryptamine 1A) receptor, and serotonergic terminals originating from the DR nucleus made symmetrical synapses with GABAergic neuronal cell bodies and dendrites within the VLO. GABAergic terminals also made symmetrical synapses with neurons expressing GABA(A) receptors and projecting to the PAG. These results suggest that a local neuronal circuit, consisting of 5-HTergic terminals, GABAergic interneurons, and projection neurons, exists in the VLO, and provides morphological evidence for the hypothesis that GABAergic modulation is involved in 5-HT(1A) receptor activation-evoked antinociception.
Huo
Fu-Quan
FQ
Department of Physiology and Pathophysiology, Key Laboratory of Environment and Genes Related to Diseases, Ministry of Education, Xi'an Jiaotong University School of Medicine, Xi'an 710061, PR China.
Chen
Tao
T
Lv
Bo-Chang
BC
Wang
Jing
J
Zhang
Ting
T
Qu
Chao-Ling
CL
Li
Yun-Qing
YQ
Tang
Jing-Shi
JS
D000818:Animals; D005625:Frontal Lobe / Q000166:cytology* / Q000502:physiology*; D008297:Male; D009415:Nerve Net / Q000166:cytology / Q000502:physiology; D009434:Neural Pathways / Q000166:cytology / Q000502:physiology; D009474:Neurons / Q000166:cytology* / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D044282:Receptor, Serotonin, 5-HT1A / Q000378:metabolism*; D013569:Synapses / Q000502:physiology* / Q000648:ultrastructure*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
D044282:Receptor, Serotonin, 5-HT1A; D005680:gamma-Aminobutyric Acid