ANALYSIS OF SYNAPTIC INPUTS AND TARGETS OF PHYSIOLOGICALLY CHARACTERIZED NEURONS IN RAT FRONTAL-CORTEX – COMBINED IN-VIVO INTRACELLULAR-RECORDING AND IMMUNOLABELING
Synapse. 1994-06-01; 17(2): 101-114
DOI: 10.1002/syn.890170206
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1. Synapse. 1994 Jun;17(2):101-14.
Analysis of synaptic inputs and targets of physiologically characterized neurons
in rat frontal cortex: combined in vivo intracellular recording and
immunolabeling.
Cowan RL(1), Sesack SR, Van Bockstaele EJ, Branchereau P, Chain J, Pickel VM.
Author information:
(1)Department of Neurology and Neuroscience, Cornell University Medical College,
New York, New York 10021.
Ultrastructural immunocytochemical identification of transmitters in afferent
terminals and targets of individual physiologically characterized neurons is
essential for understanding the complex circuitry within the mammalian neocortex.
For this type of analysis, we examined the utility of combining in vivo
intracellular recording and biocytin injections with silver intensified 1 nm
immunogold labeling of GABA and the catecholamine synthesizing enzyme, tyrosine
hydroxylase (TH). These transmitters are found to local neurons and afferents
known to prominently modulate the activity of pyramidal neurons in the neocortex.
Individual neurons were physiologically characterized and filled with biocytin in
the frontal cortex of anesthetized rats. The brains were then preserved by
vascular perfusion with aldehydes. Single vibratome sections through the
recording site were reacted (1) for immunoperoxidase detection of biocytin and
(2) for immunogold labeling of GABA or TH. Dually labeled sections were processed
for light microscopy or embedded in plastic for electron microscopy. The dense
peroxidase product for biocytin was detected in pyramidal neurons. These were
located in superficial as well as deep cortical laminae, and were readily
distinguished from immunogold silver labeling. GABA labeled terminals formed
symmetric synapses with larger biocytin filled dendrites, whereas the TH labeled
terminals contacted distal dendrites and spines. Peroxidase labeling for biocytin
also was seen in a few axon terminals forming synapses with unlabeled and with
GABA immunoreactive dendrites. These results suggest that single pyramidal
neurons of the rat frontal cortex receive dual input from both GABA and
catecholamine terminals. Additionally, this study demonstrates the usefulness of
silver enhancement of 1 nm colloidal gold prior to plastic embedding for electron
microscopic detection of neurotransmitters within afferents and targets of
neurons physiologically characterized in vivo.
DOI: 10.1002/syn.890170206
PMID: 7916489 [Indexed for MEDLINE]