Single axon fast inhibitory postsynaptic potentials elicited by a sparsely spiny interneuron in rat neocortex

doi:10.1016/0306-4522(95)00020-J

Neuroscience

Volume 65, Issue 4, April 1995, Pages 935-942

https://doi.org/10.1016/0306-4522(95)00020-J Get rights and content

Abstract

Many of the different morphological types of interneurons in mammalian neocortex are presumed to be inhibitory, but to date, conclusive functional data have been lacking. Using paired intracellular recordings in slices of adult rat somatosensory cortex, we present a sparsely spiny, burst firing interneuron that elicits in a simultaneously recorded pyramid a fast inhibitory postsynaptic potential, reversing at −78 mV. Neither inhibitory postsynaptic potential time course, nor paired pulse depression (inter-spike interval 5–120 ms), was affected by addition of the GABA_B antagonist/partial agonist 2-OH-Saclofen (250 μM), but increasing extracellular [Ca²⁺] enhanced inhibitory postsynaptic potential amplitude at low firing rates and increased paired pulse depression at higher rates. Light microscopic examination of the biocytin-filled neurons revealed the presynaptic cell to be a sparsely spiny interneuron and the postsynaptic to be a small pyramidal neuron, both in layer II. Ultrastructural examination of 16 terminals of the presynaptic interneuron revealed that they formed symmetric contacts with unlabelled neurons, four with neuronal somata, 10 with dendritic shafts and two with spine shafts. This, therefore, is the first report of the properties of a single axon inhibitory postsynaptic potential in neocortex resulting from action potentials in an electrophysiologically and morphologically identified interneuron. We propose that at least some of the sparsely spiny, burst firing interneurons inhibit pyramidal neurons via GABA_A receptors.

References (25)

D.R. Curtis et al.
Baclofen antagonism by 2-OH-saclofen in the cat spinal cord
Neurosci. Lett.
(1988)
J. DeFelipe et al.
Synapses of double bouquet cells in monkey cerebral cortex visualized by calbindin immunoreactivity
Brain Res.
(1989)
J. DeFelipe et al.
A microcolumnar structure of monkey cerebral cortex revealed by immunocytochemical studies of double bouquet cell axons
Neuroscience
(1990)
A.M. Thomson et al.
Single axon excitatory postsynaptic potentials in neocortical interneurons exhibit pronounced paired pulse facilitation
Neuroscience
(1993)
L.S. Benardo
Separate activation of fast and slow inhibitory postsynaptic potentials in rat neocortex in vitro
J. Physiol.
(1994)
E.H. Buhl et al.
Diverse sources of hippocampal unitary inhibitory postsynaptic potentials and the number of synaptic release sites
Nature
(1994)
S.J. Caddick et al.
Modulation of synaptic responses in CA1 pyramidal neurones of the rat hippocampus by activation of presynaptic GABA_B receptors
J. Physiol.
(1994)
F. Conde et al.
Local circuit neurons immunoreactive for calretinin, calbindin D-28K or parvalbumin in monkey prefrontal cortex: distribution and morphology
J. comp. Neurol.
(1994)
C.H. Davies et al.
Paired-pulse depression of monosynaptic GABA-mediated inhibitory postsynaptic responses in rat hippocampus
J. Physiol.
(1990)
J. DeFelipe et al.
High-resolution light and electron microscopic immunocytochemistry of colocalized GABA and calbindin D-28K in somata and double bouquet cell axons of monkey somatosensory cortex
Eur. J. Neurosci.
(1992)

M.R. Del Rio et al.

A study of SMI 32-stained pyramidal cells, parvalbumin-immunoreactive chandelier cells, and presumptive thalamocortical axons in the human temporal neocortex

J. comp. Neurol.

(1994)

J. Deuchars et al.

Relationships between morphology and physiology of pyramid-pyramid single axon connections in rat neocortex in vitro

J. Physiol.

(1994)

Cited by (41)

Biocytin-labelling and its impact on late 20th century studies of cortical circuitry
2011, Brain Research Reviews
Citation Excerpt :
In this article, we focus on its contribution to the understanding of cortical microcircuitry and in particular, the correlation between cell type and function. Publication of the intracellular biocytin-labelling method coincided with Jim Deuchars, a very talented young neuroanatomist, joining the Thomson lab and this method, combined with dual intracellular recordings, soon became the signature of the lab (Deuchars et al., 1994, 1996a; Deuchars and Thomson, 1995a,b; Thomson et al., 1995, 1996a,b; Ali and Thomson, 1998). Inspiration was needed to pursue this somewhat labour-intensive approach; 12–16 hour dual recording experiments, followed by 2–3 days histological processing and 1–2 weeks for neuronal reconstruction at the microscope.
In recognition of the impact that a powerful new anatomical tool, such as the Golgi method, can have, this essay highlights the enormous influence that biocytin-filling has had on modern neuroscience. This method has allowed neurones that have been recorded intracellularly, ‘whole-cell’ or juxta-cellularly, to be identified anatomically, forming a vital link between functional and structural studies. It has been applied throughout the nervous system and has become a fundamental component of our technical armoury. A comprehensive survey of the applications to which the biocytin-filling approach has been put, would fill a large volume. This essay therefore focusses on one area, neocortical microcircuitry and the ways in which combining physiology and anatomy have revealed rules that help us explain its previously indecipherable variability and complexity.
Patterns of spontaneous activity and morphology of interneuron types in organotypic cortex and thalamus-cortex cultures
1999, Neuroscience
The physiological and morphological properties of interneurons in infragranular layers of rat visual cortex have been studied in organotypic cortex monocultures and thalamus–cortex co-cultures using intracellular recordings and biocytin injections. Cultures were prepared at the day of birth and maintained for up to 20 weeks. Twenty-nine interneurons of different types were characterized, in addition to 170 pyramidal neurons. The cultures developed a considerable degree of synaptically driven “spontaneous” bioelectric activity without epileptiform activity. Interneurons in cortex monocultures and thalamus–cortex co-cultures had the same physiological and morphological properties, and also pyramidal cell properties were not different in the two culture conditions. All interneurons and the majority of pyramidal cells displayed synaptically driven action potentials. The physiological group of fast-spiking interneurons included large basket cells, columnar basket cells (two cells with an arcade axon) and horizontally bitufted cells. The physiological group of slow-spiking interneurons included Martinotti cells and a “long-axon” cell. Analyses of the temporal patterns of activity revealed that fast-spiking interneurons have higher rates of spontaneous activity than slow-spiking interneurons and pyramidal cells. Furthermore, fast-spiking interneurons fired spontaneous bursts of action potentials in the gamma frequency range.
We conclude from these findings that physiological and morphological properties of interneurons in organotypic mono- and co-cultures match those of interneurons characterized in vivo or in acute slice preparations, and they maintain in long-term cultures a well-balanced state of excitation and inhibition. This suggests that cortex-intrinsic or cell-autonomous mechanisms are sufficient for the expression of cell type-specific electrophysiological properties in the absence of afferents or sensory input.
Preservation of ultrastructure and antigenicity for EM immunocytochemistry following intracellular recording and labeling of single cortical neurons in brain slices
1998, Journal of Neuroscience Methods
Knowledge of the distribution of neurotransmitters, neuromodulators, and transmitter receptors operating at specific synaptic sites on cortical neurons is essential for understanding the precise mechanisms that underlie the dynamic properties of cortical microcircuitry. We report on a new combination of techniques for analyzing chemically-specified synaptic input to individual cortical neurons first electrophysiologically characterized in the in vitro brain slice preparation. We tested the feasibility of this approach by performing intracellular recordings and biocytin injections in guinea pig medial prefrontal cortex slices and then by performing dual preembedding immunocytochemistry in order to localize neuronal nitric oxide synthase relative to single biocytin-filled neurons. The recorded cell and nitric oxide synthase immunoreactivity were visualized by light and electron microscopy utilizing both peroxidase and silver intensified gold stains. Single neurons were also dually visualized with fluorescence for light microscopy and with silver intensified gold for electron microscopy. Our findings indicate that both antigenicity and ultrastructure can be well preserved in tissue first used for in vitro slice experiments. This combination of methods should be widely applicable for analyzing the subcellular distribution of neuronal molecules such as receptors, channels and enzymes on physiologically characterized mammalian neurons.
Salient features of synaptic organisation in the cerebral cortex
1998, Brain Research Reviews
The neuronal and synaptic organisation of the cerebral cortex appears exceedingly complex, and the definition of a basic cortical circuit in terms of defined classes of cells and connections is necessary to facilitate progress of its analysis. During the last two decades quantitative studies of the synaptic connectivity of identified cortical neurones and their molecular dissection revealed a number of general rules that apply to all areas of cortex. In this review, first the precise location of postsynaptic GABA and glutamate receptors is examined at cortical synapses, in order to define the site of synaptic interactions. It is argued that, due to the exclusion of G protein-coupled receptors from the postsynaptic density, the presence of extrasynaptic receptors and the molecular compartmentalisation of the postsynaptic membrane, the synapse should include membrane areas beyond the membrane specialisation. Subsequently, the following organisational principles are examined:
- 1.
  The cerebral cortex consists of: (i) a large population of principal neurones reciprocally connected to the thalamus and to each other via axon collaterals releasing excitatory amino acids, and, (ii) a smaller population of mainly local circuit GABAergic neurones.
- 2.
  Differential reciprocal connections are also formed amongst GABAergic neurones.
- 3.
  All extrinsic and intracortical glutamatergic pathways terminate on both the principal and the GABAergic neurones, differentially weighted according to the pathway.
- 4.
  Synapses of multiple sets of glutamatergic and GABAergic afferents subdivide the surface of cortical neurones and are often co-aligned on the dendritic domain.
- 5.
  A unique feature of the cortex is the GABAergic axo-axonic cell, influencing principal cells through GABA_A receptors at synapses located exclusively on the axon initial segment.
The analysis of these salient features of connectivity has revealed a remarkably selective array of connections, yet a highly adaptable design of the basic circuit emerges when comparisons are made between cortical areas or layers. The basic circuit is most obvious in the hippocampus where a relatively homogeneous set of spatially aligned principal cells allows an easy visualization of the organisational rules. Those principles which have been examined in the isocortex proved to be identical or very similar. In the isocortex, the basic circuit, scaled to specific requirements, is repeated in each layer. As multiple sets of output neurones evolved, requiring subtly different needs for their inputs, the basic circuit may be superimposed several times in the same layer. Tangential intralaminar connections in both the hippocampus and isocortex also connect output neurones with similar properties, as best seen in the patchy connections in the isocortex. The additional radial superposition of several laminae of distinct sets of output neurones, each representing and supported by its basic circuit, requires a co-ordination of their activity that is mediated by highly selective interlaminar connections, involving both the GABAergic and the excitatory amino acid releasing neurones. The remarkable specificity in the geometry of cells and the selectivity in placement of neurotransmitter receptors and synapses on their surface, strongly suggest a predominant role for time in the coding of information, but this does not exclude an important role also for the rate of action potential discharge in cortical representation of information.
Neurochemical features and synaptic connections of large physiologically-identified GABAergic cells in the rat frontal cortex
1998, Neuroscience
Physiological and morphological properties of large non-pyramidal cells immunoreactive for cholecystokinin, parvalbumin or somatostatin were investigated in vitro in the frontal cortex of 18–22-day-old rats. These three peptides were expressed in separate populations including large cells. Cholecystokinin cells and parvalbumin cells made boutons apposed to other cell bodies, but differed in their firing patterns in response to depolarizing current pulses. Parvalbumin cells belonged to fast-spiking cells. Parvalbumin fast-spiking cells also included chandelier cells. In contrast, cholecystokinin cells were found to be regular-spiking non-pyramidal cells or burst-spiking non-pyramidal cells with bursting activity from hyperpolarized potentials (two or more spikes on slow depolarizing humps). Large somatostatin cells belonged to the regular-spiking non-pyramidal category and featured wide or ascending axonal arbors (wide arbor cells and Martinotti cells) which did not seem to be apposed to the somata so frequently as large cholecystokinin and parvalbumin cells. For electron microscopic observations, another population of eight immunohistochemically-uncharacterized non-pyramidal cells were selected: (i) five fast spiking cells including one chandelier cell which are supposed to contain parvalbumin, and (ii) three large regular-spiking non-pyramidal cells with terminals apposed to somata, which are not considered to include somatostatin cells, but some of which may belong to cholecystokinin cells. The fast-spiking cells other than a chandelier cell and the large regular-spiking non-pyramidal cells made GABA-positive synapses on somata (4% and 12% of the synapses in two small to medium fast-spiking cells, 22% and 35% of the synapses in two large fast-spiking cells, and 10%, 18% and 37% of the synapses in three large regular-spiking non-pyramidal cells). A few terminals of the fast-spiking and regular-spiking non-pyramidal cells innervated GABAergic cells. About 30% of the fast-spiking cell terminals innervated spines, but few of the regular-spiking non-pyramidal cell terminals did. A fast-spiking chandelier cell made GABA-positive synapses on GABA-negative axon initial segments.
These results suggest that large GABAergic cells are heterogeneous in neuroactive substances, firing patterns and synaptic connections, and that cortical cells receive heterogeneous GABAergic somatic inputs.
Improved biocytin labeling and neuronal 3D reconstruction
2012, Nature Protocols

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Abstract

References (25)

Baclofen antagonism by 2-OH-saclofen in the cat spinal cord

Neurosci. Lett.

Synapses of double bouquet cells in monkey cerebral cortex visualized by calbindin immunoreactivity

Brain Res.

A microcolumnar structure of monkey cerebral cortex revealed by immunocytochemical studies of double bouquet cell axons

Neuroscience

Single axon excitatory postsynaptic potentials in neocortical interneurons exhibit pronounced paired pulse facilitation

Neuroscience

Separate activation of fast and slow inhibitory postsynaptic potentials in rat neocortex in vitro

J. Physiol.

Diverse sources of hippocampal unitary inhibitory postsynaptic potentials and the number of synaptic release sites

Nature

Modulation of synaptic responses in CA1 pyramidal neurones of the rat hippocampus by activation of presynaptic GABA_B receptors

J. Physiol.

Local circuit neurons immunoreactive for calretinin, calbindin D-28K or parvalbumin in monkey prefrontal cortex: distribution and morphology

J. comp. Neurol.

Paired-pulse depression of monosynaptic GABA-mediated inhibitory postsynaptic responses in rat hippocampus

J. Physiol.

High-resolution light and electron microscopic immunocytochemistry of colocalized GABA and calbindin D-28K in somata and double bouquet cell axons of monkey somatosensory cortex

Eur. J. Neurosci.

A study of SMI 32-stained pyramidal cells, parvalbumin-immunoreactive chandelier cells, and presumptive thalamocortical axons in the human temporal neocortex

J. comp. Neurol.

Relationships between morphology and physiology of pyramid-pyramid single axon connections in rat neocortex in vitro

J. Physiol.

Cited by (41)

Biocytin-labelling and its impact on late 20th century studies of cortical circuitry

Patterns of spontaneous activity and morphology of interneuron types in organotypic cortex and thalamus-cortex cultures

Preservation of ultrastructure and antigenicity for EM immunocytochemistry following intracellular recording and labeling of single cortical neurons in brain slices

Salient features of synaptic organisation in the cerebral cortex

Neurochemical features and synaptic connections of large physiologically-identified GABAergic cells in the rat frontal cortex

Improved biocytin labeling and neuronal 3D reconstruction

Letter to neuroscienceSingle axon fast inhibitory postsynaptic potentials elicited by a sparsely spiny interneuron in rat neocortex

Abstract

Neurosci. Lett.

Brain Res.

Neuroscience

Neuroscience

Separate activation of fast and slow inhibitory postsynaptic potentials in rat neocortex in vitro

J. Physiol.

Diverse sources of hippocampal unitary inhibitory postsynaptic potentials and the number of synaptic release sites

Nature

Modulation of synaptic responses in CA1 pyramidal neurones of the rat hippocampus by activation of presynaptic GABAB receptors

J. Physiol.

Local circuit neurons immunoreactive for calretinin, calbindin D-28K or parvalbumin in monkey prefrontal cortex: distribution and morphology

J. comp. Neurol.

Paired-pulse depression of monosynaptic GABA-mediated inhibitory postsynaptic responses in rat hippocampus

J. Physiol.

High-resolution light and electron microscopic immunocytochemistry of colocalized GABA and calbindin D-28K in somata and double bouquet cell axons of monkey somatosensory cortex

Eur. J. Neurosci.

A study of SMI 32-stained pyramidal cells, parvalbumin-immunoreactive chandelier cells, and presumptive thalamocortical axons in the human temporal neocortex

J. comp. Neurol.

Relationships between morphology and physiology of pyramid-pyramid single axon connections in rat neocortex in vitro

J. Physiol.

Letter to neuroscience
Single axon fast inhibitory postsynaptic potentials elicited by a sparsely spiny interneuron in rat neocortex

Modulation of synaptic responses in CA1 pyramidal neurones of the rat hippocampus by activation of presynaptic GABA_B receptors