Although considerable evidence suggests that the chemical synapse is a lynchpin underlying affective disorders, how molecular insults differentially affect specific synaptic connections remains ...poorly understood. For instance, Neurexin 1a and 2 (NRXN1 and NRXN2) and CNTNAP2 (also known as CASPR2), all members of the neurexin superfamily of transmembrane molecules, have been implicated in neuropsychiatric disorders. However, their loss leads to deficits that have been best characterized with regard to their effect on excitatory cells. Notably, other disease-associated genes such as BDNF and ERBB4 implicate specific interneuron synapses in psychiatric disorders. Consistent with this, cortical interneuron dysfunction has been linked to epilepsy, schizophrenia and autism. Using a microarray screen that focused upon synapse-associated molecules, we identified Cntnap4 (contactin associated protein-like 4, also known as Caspr4) as highly enriched in developing murine interneurons. In this study we show that Cntnap4 is localized presynaptically and its loss leads to a reduction in the output of cortical parvalbumin (PV)-positive GABAergic (γ-aminobutyric acid producing) basket cells. Paradoxically, the loss of Cntnap4 augments midbrain dopaminergic release in the nucleus accumbens. In Cntnap4 mutant mice, synaptic defects in these disease-relevant neuronal populations are mirrored by sensory-motor gating and grooming endophenotypes; these symptoms could be pharmacologically reversed, providing promise for therapeutic intervention in psychiatric disorders.
The kinetics of GABAergic synaptic currents can vary by an order of magnitude depending on the cell type. The neurogliaform cell (NGFC) has recently been identified as a key generator of slow GABA(A) ...receptor-mediated volume transmission in the isocortex. However, the mechanisms underlying slow GABA(A) receptor-mediated IPSCs and their use-dependent plasticity remain unknown. Here, we provide experimental and modeling data showing that hippocampal NGFCs generate an unusually prolonged (tens of milliseconds) but low-concentration (micromolar range) GABA transient, which is responsible for the slow response kinetics and which leads to a robust desensitization of postsynaptic GABA(A) receptors. This strongly contributes to the use-dependent synaptic depression elicited by various patterns of NGFC activity including the one detected during theta network oscillations in vivo. Synaptic depression mediated by NGFCs is likely to play an important modulatory role in the feedforward inhibition of CA1 pyramidal cells provided by the entorhinal cortex.
Ventral telencephalic progenitors expressing the homeodomain transcription factor Nkx6-2 have been shown to give rise to a multitude of cortical interneuron subtypes usually associated with origin in ...either the medial ganglionic eminence or the caudal ganglionic eminence. The function of Nkx6-2 in directing the fate of those progenitors has, however, not been thoroughly analyzed. We used a combination of genetic inducible fate mapping and in vivo loss-of-function to analyze the requirement of Nkx6-2 in determining the fate of cortical interneurons. We have found that interneuron subtypes are born with a characteristic temporal pattern. Furthermore, we extend the characterization of interneurons from the Nkx6-2 lineage through the application of electrophysiological methods. Analysis of these populations in Nkx6-2 null mice suggests that there is a small and partially penetrant loss of delayed non-fast spiking somatostatin/calretinin double positive cortical interneurons in the absence of Nkx6-2 gene function.
By combining an inducible genetic fate mapping strategy with electrophysiological analysis, we have systematically characterized the populations of cortical GABAergic interneurons that originate from ...the caudal ganglionic eminence (CGE). Interestingly, compared with medial ganglionic eminence (MGE)-derived cortical interneuron populations, the initiation embryonic day 12.5 (E12.5) and peak production (E16.5) of interneurons from this embryonic structure occurs 3 d later in development. Moreover, unlike either pyramidal cells or MGE-derived cortical interneurons, CGE-derived interneurons do not integrate into the cortex in an inside-out manner but preferentially (75%) occupy superficial cortical layers independent of birthdate. In contrast to previous estimates, CGE-derived interneurons are both considerably greater in number (approximately 30% of all cortical interneurons) and diversity (comprised by at least nine distinct subtypes). Furthermore, we found that a large proportion of CGE-derived interneurons, including the neurogliaform subtype, express the glycoprotein Reelin. In fact, most CGE-derived cortical interneurons express either Reelin or vasoactive intestinal polypeptide. Thus, in conjunction with previous studies, we have now determined the spatial and temporal origins of the vast majority of cortical interneuron subtypes.
Abstract
Neuronal circuits of the spinal dorsal horn integrate sensory information from the periphery with inhibitory and facilitating input from higher central nervous system areas. Most previous ...work focused on projections descending from the hindbrain. Less is known about inputs descending from the cerebral cortex. Here, we identified cholecystokinin (CCK) positive layer 5 pyramidal neurons of the primary somatosensory cortex (CCK + S1-corticospinal tract CST neurons) as a major source of input to the spinal dorsal horn. We combined intersectional genetics and virus-mediated gene transfer to characterize CCK+ S1-CST neurons and to define their presynaptic input and postsynaptic target neurons. We found that S1-CST neurons constitute a heterogeneous population that can be subdivided into distinct molecular subgroups. Rabies-based retrograde tracing revealed monosynaptic input from layer 2/3 pyramidal neurons, from parvalbumin positive cortical interneurons, and from thalamic relay neurons in the ventral posterolateral nucleus. Wheat germ agglutinin-based anterograde tracing identified postsynaptic target neurons in dorsal horn laminae III and IV. About 60% of these neurons were inhibitory and about 60% of all spinal target neurons expressed the transcription factor c-Maf. The heterogeneous nature of both S1-CST neurons and their spinal targets suggest complex roles in the fine-tuning of sensory processing.
Abstract
Zolpidem is a hypnotic benzodiazepine site agonist with some γ‐aminobutyric acid (GABA)
A
receptor subtype selectivity. Here, we have tested the effects of zolpidem on the hippocampus of γ2 ...subunit (γ2F77I) point mutant mice. Analysis of forebrain GABA
A
receptor expression with immunocytochemistry, quantitative
3
Hmuscimol and
35
S t‐butylbicyclophosphorothionate (TBPS) autoradiography, membrane binding with
3
Hflunitrazepam and
3
Hmuscimol, and comparison of miniature inhibitory postsynaptic current (mIPSC) parameters did not reveal any differences between homozygous γ2I77/I77 and γ2F77/F77 mice. However, quantitative immunoblot analysis of γ2I77/I77 hippocampi showed some increased levels of γ2, α1, α4 and δ subunits, suggesting that differences between strains may exist in unassembled subunit levels, but not in assembled receptors. Zolpidem (1 µ
m
) enhanced the decay of mIPSCs in CA1 pyramidal cells of control (C57BL/6J, γ2F77/F77) mice by ∼ 60%, and peak amplitude by ∼ 20% at 33–34 °C
in vitro
. The actions of zolpidem (100 n
m
or 1 µ
m
) were substantially reduced in γ2I77/I77 mice, although residual effects included a 9% increase in decay and 5% decrease in peak amplitude. Similar results were observed in CA1 stratum oriens/alveus interneurons. At network level, the effect of zolpidem (10 µ
m
) on carbachol‐induced oscillations in the CA3 area of γ2I77/I77 mice was significantly different compared with controls. Thus, the γ2F77I point mutation virtually abolished the actions of zolpidem on GABA
A
receptors in the hippocampus. However, some residual effects of zolpidem may involve receptors that do not contain the γ2 subunit.
The ionization state of Leu-enkephalin in DMSO and MeCN/DMSO (4/1) solution was studied by the combined use of
17O NMR and FT-IR spectroscopy. After lyophilization or an aqueous solution at nearly ...neutral pH, Leu-enkephalin essentially exists in the uncharged state in MeCN/DMSO (4/1) solution. In pure DMSO, only 40% of the Leu-enkephalin molecules are in the zwitterionic state under the same conditions.
Zolpidem is a hypnotic benzodiazepine site agonist with some gamma -aminobutyric acid (GABA) sub(A) receptor subtype selectivity. Here, we have tested the effects of zolpidem on the hippocampus of ...gamma 2 subunit ( gamma 2F77I) point mutant mice. Analysis of forebrain GABA sub(A) receptor expression with immunocytochemistry, quantitative super(3)Hmuscimol and super(35)S t-butylbicyclophosphorothionate (TBPS) autoradiography, membrane binding with super(3)Hflunitrazepam and super(3)Hmuscimol, and comparison of miniature inhibitory postsynaptic current (mIPSC) parameters did not reveal any differences between homozygous gamma 2I77-I77 and gamma 2F77-F77 mice. However, quantitative immunoblot analysis of gamma 2I77-I77 hippocampi showed some increased levels of gamma 2, alpha 1, alpha 4 and delta subunits, suggesting that differences between strains may exist in unassembled subunit levels, but not in assembled receptors. Zolpidem (1 mu m) enhanced the decay of mIPSCs in CA1 pyramidal cells of control (C57BL-6J, gamma 2F77-F77) mice by similar to 60%, and peak amplitude by similar to 20% at 33-34 degree C in vitro. The actions of zolpidem (100 nm or 1 mu m) were substantially reduced in gamma 2I77-I77 mice, although residual effects included a 9% increase in decay and 5% decrease in peak amplitude. Similar results were observed in CA1 stratum oriens-alveus interneurons. At network level, the effect of zolpidem (10 mu m) on carbachol-induced oscillations in the CA3 area of gamma 2I77-I77 mice was significantly different compared with controls. Thus, the gamma 2F77I point mutation virtually abolished the actions of zolpidem on GABA sub(A) receptors in the hippocampus. However, some residual effects of zolpidem may involve receptors that do not contain the gamma 2 subunit.
Zolpidem is a hypnotic benzodiazepine site agonist with some gamma-aminobutyric acid (GABA)(A) receptor subtype selectivity. Here, we have tested the effects of zolpidem on the hippocampus of gamma2 ...subunit (gamma2F77I) point mutant mice. Analysis of forebrain GABA(A) receptor expression with immunocytochemistry, quantitative (3)Hmuscimol and (35)S t-butylbicyclophosphorothionate (TBPS) autoradiography, membrane binding with (3)Hflunitrazepam and (3)Hmuscimol, and comparison of miniature inhibitory postsynaptic current (mIPSC) parameters did not reveal any differences between homozygous gamma2I77/I77 and gamma2F77/F77 mice. However, quantitative immunoblot analysis of gamma2I77/I77 hippocampi showed some increased levels of gamma2, alpha1, alpha4 and delta subunits, suggesting that differences between strains may exist in unassembled subunit levels, but not in assembled receptors. Zolpidem (1 microm) enhanced the decay of mIPSCs in CA1 pyramidal cells of control (C57BL/6J, gamma2F77/F77) mice by approximately 60%, and peak amplitude by approximately 20% at 33-34 degrees C in vitro. The actions of zolpidem (100 nm or 1 microm) were substantially reduced in gamma2I77/I77 mice, although residual effects included a 9% increase in decay and 5% decrease in peak amplitude. Similar results were observed in CA1 stratum oriens/alveus interneurons. At network level, the effect of zolpidem (10 microm) on carbachol-induced oscillations in the CA3 area of gamma2I77/I77 mice was significantly different compared with controls. Thus, the gamma2F77I point mutation virtually abolished the actions of zolpidem on GABA(A) receptors in the hippocampus. However, some residual effects of zolpidem may involve receptors that do not contain the gamma2 subunit.
PDF
