GABAergic neurons containing CCK‐8‐like and/or VIP‐like immunoreactivities in the rat hippocampus and dentate gyrus

Abstract

The coexistence of cholecystokinin-octapeptide-like (CCK-L) and/or vasoactive-intestinal-polypeptide-like immunoreactive (VIP-LI) materials and glutamate decarboxylase (GAD) was studied in the rat hippocampus and dentate gyrus by means of immunohistochemistry. Consecutive 40-micron-thick sections were incubated in different antisera and those cells which were bisected by the plane of sectioning so as to be included at the paired surfaces of two adjacent sections were identified. The coexistence of the immunoreactivities for these peptides and GAD in the same cell could thus be determined by observing the immunoreactivity of the two halves of the cell, incubated in two different antisera. Almost all of the CCK-LI neurons were also GAD immunoreactive, whereas only about 10% of the GAD-immunoreactive neurons were CCK-LI. The percentages of GAD-immunoreactive neurons which were also immunoreactive for CCK were dependent on the laminar area in which they were found: i.e., 15-20% in the stratum radiatum of the hippocampus, about 10% in the stratum pyramidale, and about 6% in the stratum oriens. In contrast to the CCK-LI neurons, only about 40% of the VIP-LI neurons were identified to be also GAD immunoreactive, which might correspond to only part of the GAD-immunoreactive neurons. Furthermore the coexistence of VIP-LI and CCK-LI materials was recognized in about 10% of the CCK-LI neurons or about 35% of the VIP-LI neurons, indicating that some GABAergic neurons (presumably about 1%) in the rat hippocampus and dentate gyrus may contain both CCK-LI and VIP-LI materials.

GABAergic neurons in the rat hippocampal formation: ultrastructure and synaptic relationships with catecholaminergic terminals

“…The morphological features of neurons with GABA-LI were similar to those reported previously in the hippocampus using GABA or GAD antibodies in the rat (Frotscher et al, 1984;Kosaka et al, 1984;Frotscher and Zimmer, 1987;Leranth and Frotscher, 1987a, b) and human (Schlander et al, 1987). It is interesting that the ultrastructural characteristics of GABAergic neurons did not differ significantly between the hippocampus and DG since GABAergic perikarya have been divided into several subclasses based on light microscopic distribution and morphological characteristics (Seress and Ribak, 1983) and colocalization with other neurotransmitters (Somogyi et al, 1984;Kosaka et al, 1985;Kunkel and Schwartzkroin, 1988) or proteins (Kosaka et al, 1987a).…”

“…The presence of dcvs amidst unlabeled smaller vesicles raises the prospect that GABA may be colocalized in these terminals with other transmitters. Cholecystokinin, vasoactive intestinal peptide, and somatostatin are possible candidates since these substances coexist within GABAergic neurons in the hippocampal formation (Somogyi et al, 1984;Kosaka et al, 1985;Kunkel and Schwartzkroin, 1988).…”

Nucleus Reuniens Thalami Modulates Activity in Hippocampal Field CA1 through Excitatory and Inhibitory Mechanisms

“…Functionally, they are assumed to mediate both feedforward and feedback inhibition of pyramidal cells (Lacaille et al, 1987;Lacaille and Schwarzkroin, 1988;Samulack et al, 1993). Interneurons located in the distal radiatum that f ulfill the criterion to receive RE input are likely the ones containing GABA as well as the putative excitatory transmitters cholecystokinin (CCK) and /or vasoactive intestinal polypeptide (V I P) (Kosaka et al, 1985;Gulyás et al, 1991;Haas and Gáhwiler, 1992;Acsády et al, 1996a,b). GABA-CCK cells have been observed to form symmetrical synapses with pyramidal cell bodies (Harris et al, 1985;Nunzi et al, 1985); GABA-V I P cells have been shown to contact primarily other interneurons (Acsády et al, 1996a,b;Freund and Buzsáki, 1996).…”

GABAergic interneurons are the targets of cannabinoid actions in the human hippocampus

“…20,22 Adjacent sections were reacted for CB1 and for one of the other antigens, and bisected cell bodies were identified on the common surfaces of both sections using capillaries as landmarks using a ×100 oil immersion objective. Cells were only included in the analysis if both matching halves could be unequivocally identified (whether negative or positive).…”