title: Morphological heterogeneity of non-pyramidal neurons in the CA1 region of the rat hippocampus.
abstract: Using techniques of combining intracellular recording and intracellular staining with biocytin, 19 neurons have been sampled within or close to the CA1 pyramidal cell layer in hippocampal slices of the rat. All of these cells were physiologically characterized as non-pyramidal or interneurons based on their action potential properties and responses to somatic depolarization. After injection of biocytin into these identified cells, all these cells were morphologically confirmed as non-pyramidal cells. Five cell types were distinguished according to the distribution patterns of their axon trees and locations of the somata. (1) Basket cells (n = 10) with somata located within or close to the pyramidal cell layer had axon arborizations restricted in the same layer. (2) Chandelier cell somata (n = 3) were located in the pyramidal cell layer and their axon arborizations were selectively distributed in the deep stratum oriens (adjacent to the pyramidal cell layer), where axon initial segments of pyramidal cell were located. (3) Three neurons recorded from the deep stratum oriens had axon trees covering both the pyramidal cell layer and the deep stratum oriens (n = 2) or mainly projecting to the distal stratum radiatum and stratum lacunosum-moleculare (n = 1). (4) Two axodendritic cells with somata located in the pyramidal cell layer had axon trees spanning over the stratum oriens and radiatum. (5) One interneuron, like a basket cell, had an axon tree confined in the pyramidal cell layer, but its beaded axon terminals selectively contacted with the somata of the presumed non-pyramidal cells in the pyramidal cell layer, instead of pyramidal cells. These results provide further evidence that CA1 interneurons are heterogeneous with respect to the laminar distributions of their axon terminals in this region. These specific patterns of interneuron axon trees reflect the selectivity of CA1 interneurons in the postsynaptic domains of the target cells, which may be functionally associated with differential neuronal activities.
authors.affiliation: Department of Neurobiology, Fourth Military Medical University, Peoples Republic of China.
authors.forename: Z S
authors.initials: ZS
authors.lastname: Han
mesh_terms: D000818:Animals; D001369:Axons / Q000502:physiology; D001710:Biotin / Q000494:pharmacology; D003712:Dendrites / Q000502:physiology; D004594:Electrophysiology; D005260:Female; D006624:Hippocampus / Q000166:cytology*; D007395:Interneurons / Q000166:cytology* / Q000502:physiology / Q000648:ultrastructure; D008297:Male; D008839:Microelectrodes; D008845:Microinjections; D009924:Organ Culture Techniques; D011153:Population; D017966:Pyramidal Cells / Q000166:cytology / Q000502:physiology / Q000648:ultrastructure; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D001710:Biotin