title: Proportion of parvalbumin-positive basket cells in the GABAergic innervation of pyramidal and granule cells of the rat hippocampal formation.
abstract: Recent studies have indicated that hippocampal GABAergic neurons in both the dentate gyrus and Ammon's horn contain immunoreactivity for the calcium-binding protein parvalbumin (PARV). Although the distribution of PARV-positive neurons has been previously described, detailed quantitative electron microscopic studies of the PARV-positive axon terminals in the hippocampal formation are lacking. In the present study, immunocytochemical methods were used to localize PARV-positive neurons and axon terminals to determine their similarity to GABAergic neurons. The PARV-positive cells and axon terminals are associated closely with the pyramidal and granule cell layers. In agreement with previous studies, the morphology of PARV-positive neurons is similar to that of GABAergic cells, including the basket cells of both the dentate gyrus and Ammon's horn. The PARV-positive axon terminals form exclusively symmetric synapses with somata, dendrites, dendritic spines, and axon initial segments. However, these terminals represent only a portion of the total number of terminals that form symmetric synapses. Quantitative results indicate that only 32-38% of the total number of terminals forming symmetric axosomatic synapses with principal cells of the dentate gyrus and Ammon's horn are PARV positive. Together with previous findings from light microscopic double-labeling studies, these data indicate that the PARV-positive terminals arise from a subpopulation of GABAergic hippocampal neurons. Finally, it is important to note that the terminal plexus of PARV-positive hippocampal axons overlaps at all postsynaptic sites with a plexus of PARV-negative axons.
authors: Department of Anatomy and Neurobiology, University of California, Irvine 92717.
authors: C E
authors: CE
authors: Ribak
authors: R
authors: R
authors: Nitsch
authors: L
authors: L
authors: Seress
mesh_terms: D000818:Animals; D006624:Hippocampus / Q000737:chemistry / Q000166:cytology*; D008854:Microscopy, Electron; D009411:Nerve Endings / Q000737:chemistry; D009474:Neurons / Q000737:chemistry / Q000648:ultrastructure; D010320:Parvalbumins / Q000032:analysis*; D051381:Rats; D011919:Rats, Inbred Strains; D005680:gamma-Aminobutyric Acid / Q000502:physiology*
chemical_list: D010320:Parvalbumins; D005680:gamma-Aminobutyric Acid