Parvalbumin-containing cells of the angular portion of the vertical limb terminate on calbindin-immunoreactive neurons located at the border between the lateral and medial septum of the rat.
In the septal complex, both parvalbumin and calbindin neurons cocontain GABA. In the same area, a large number of GABA-GABA synaptic connections can be observed. In order to further characterize their neurochemical nature, as well as the extrinsic and/or intrinsic origin of these GABA terminals, the following experiments were performed: (1) correlated light- and electron-microscopic double immunostaining for calbindin and parvalbumin on septal sections of control rats: (2) light microscopic parvalbumin immunostaining of septal sections after surgical isolation (5 days) of the septum from its telencephalic or (3) hypothalamic afferents; and (4) parvalbumin immunostaining of sections prepared from the entire brain 2 days following horseradish peroxidase injection into the border between the lateral and medial septum. The results demonstrated that: (1) in a well-circumscribed, vertically longitudinal area located between the lateral and medial septum, 0.1-0.6 mm anterior to the bregma, a group of calbindin-containing, nonsomatospiny neurons are surrounded by parvalbumin-immunoreactive baskets; (2) these basket-forming axon terminals establish symmetric synaptic contacts with their targets; and (3) their cells of origin are not in the medial septum, but in the angular portion of the vertical limb. These observations indicate that a portion of the septal complex GABA-GABA synaptic connections represent functional interaction between two different types of GABAergic neurons. The presynaptic GABAergic neurons contain parvalbumin, and the postsynaptic GABAergic cells are immunoreactive for calbindin. Furthermore, a population of the medial septum/diagonal band parvalbumin neurons project only to the hippocampus, while others, which may also send axons to the hippocampus, terminate on lateral septum calbindin cells as well.
Kiss
J
J
Joint Research Organization of the Hungarian Academy of Sciences and Semmelweis Medical University, Neuroendocrine Unit, Budapest, Hungary.
Borhegyi
Z
Z
Csaky
A
A
Szeiffert
G
G
Leranth
C
C
D000818:Animals; D064026:Calbindins; D005260:Female; D005625:Frontal Lobe / Q000737:chemistry* / Q000166:cytology; D008297:Male; D016253:Microscopy, Immunoelectron; D009419:Nerve Tissue Proteins / Q000032:analysis*; D009474:Neurons / Q000737:chemistry*; D010320:Parvalbumins / Q000032:analysis*; D051381:Rats; D017207:Rats, Sprague-Dawley; D064030:S100 Calcium Binding Protein G / Q000032:analysis*; D012688:Septum Pellucidum / Q000737:chemistry* / Q000166:cytology
D064026:Calbindins; D009419:Nerve Tissue Proteins; D010320:Parvalbumins; D064030:S100 Calcium Binding Protein G