TY - JOUR
T1 - Morphology of identified interneurons in the CA1 regions of guinea pig hippocampus
AU - Schwartzkroin, Philip A
AU - Kunkel, D. D.
PY - 1985
Y1 - 1985
N2 - Identified interneurons in the CA1 region of guinea pig hippocampus were examined using light and electron microscopic (EM) techniques. The HRP was intracellularly injected into cells, recorded in the in vitro slice preparation, which met physiological criteria for interneurons. These neurons were characterized at the light and electron microscopic level, and used as standards for identifying interneurons which had not been HRP-labeled. Pyramidal basket cell somata were found in stratum oriens and stratum pyramidale; they were easily identifiable by their convoluted nucleus, dense endoplasmic reticulum, and numerous organelles. Aspinous dendrites reached into strata radiatum and lacunosum/moleculare, as well as ramifying within stratum oriens, where they received profuse synaptic input (primarily asymmetric synapses). Many of the asymmetric synapses degenerated following commissural lesions, suggesting that much of the input to interneurons was from extrinsic afferents. Dendrites were characterized by their spindled appearance, especially at distal sites. They showed postsynaptic degenerative changes following commissural lesions. Interneuron axons were extremely fine, with regular enlargements or 'beads' which made apparent synaptic contacts primarily on pyramidal cell somata. The axon of a single, HRP-injected interneuron made many apparent contacts on large numbers of pyramidal cells; axons arborized over distances of several hundred micra within stratum pyramidale. This study provides direct evidence that neurons, with an identified inhibitory interneuron function in hippocampus, can mediate feed-forward as well as feed-back (recurrent) inhibition. Interneuron output showed extreme divergence, with influence over large distances. The high density of intracellular organelles in these cells suggested high metabolic activity and demand, perhaps making these interneurons exceptionally vulnerable to trauma-induced damage.
AB - Identified interneurons in the CA1 region of guinea pig hippocampus were examined using light and electron microscopic (EM) techniques. The HRP was intracellularly injected into cells, recorded in the in vitro slice preparation, which met physiological criteria for interneurons. These neurons were characterized at the light and electron microscopic level, and used as standards for identifying interneurons which had not been HRP-labeled. Pyramidal basket cell somata were found in stratum oriens and stratum pyramidale; they were easily identifiable by their convoluted nucleus, dense endoplasmic reticulum, and numerous organelles. Aspinous dendrites reached into strata radiatum and lacunosum/moleculare, as well as ramifying within stratum oriens, where they received profuse synaptic input (primarily asymmetric synapses). Many of the asymmetric synapses degenerated following commissural lesions, suggesting that much of the input to interneurons was from extrinsic afferents. Dendrites were characterized by their spindled appearance, especially at distal sites. They showed postsynaptic degenerative changes following commissural lesions. Interneuron axons were extremely fine, with regular enlargements or 'beads' which made apparent synaptic contacts primarily on pyramidal cell somata. The axon of a single, HRP-injected interneuron made many apparent contacts on large numbers of pyramidal cells; axons arborized over distances of several hundred micra within stratum pyramidale. This study provides direct evidence that neurons, with an identified inhibitory interneuron function in hippocampus, can mediate feed-forward as well as feed-back (recurrent) inhibition. Interneuron output showed extreme divergence, with influence over large distances. The high density of intracellular organelles in these cells suggested high metabolic activity and demand, perhaps making these interneurons exceptionally vulnerable to trauma-induced damage.
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M3 - Article
C2 - 2982925
AN - SCOPUS:0021969618
VL - 232
SP - 205
EP - 218
JO - Journal of Comparative Neurology
JF - Journal of Comparative Neurology
SN - 0021-9967
IS - 2
ER -