Biology subjects

Heistek, T. S.

Publications and source records attributed to Heistek, T. S..

7 recordsLinked to original sources

bioRxiv2023

Lateral hypothalamic GABAergic neurons encode alcohol memories.

In alcohol use disorder the alcohol memories persist during abstinence, and exposure to stimuli associated with alcohol use can lead to relapse. This highlights the importance of investigating the neural substrates underlying not only relapse, but also encoding and expression of alcohol memories. GABAergic neurons in the Lateral Hypothalamus (LH- GABA) have been shown to be critical for food-cue memories and motivation, however the extent to which this role extends to alcohol-cue memories and motivations remains unexplored. In this study, we aimed to describe how alcohol related memories are encoded and expressed in LH GABAergic neurons. Our first step was to monitor LH-GABA calcium transients during acquisition, extinction, and reinstatement of an alcohol-cue memory using fiber photometry. We trained the rats on a Pavlovian conditioning task where one conditioned stimulus (CS+) predicted alcohol (20% EtOH) and another conditioned stimulus (CS-) had no outcome. We then extinguished this association through non-reinforced presentations of the CS+ and CS-, finally in two different groups we measured relapse under non-primed and alcohol primed induced reinstatement. Our results show that initially both cues caused increased LH-GABA activity, and after learning only the alcohol-cue increased LH-GABA activity. After extinction this activity decreases, and we found no differences in LH- GABA activity during reinstatement in either group. Next, inhibited LH-GABA neurons with optogenetics to show that activity of these neurons is necessary for the formation of an alcohol-cue associations. These findings suggest that LH-GABA might be involved in attentional processes modulated by learning.

neuroscience↗

bioRxiv2022

Structural and functional specializations of human fast spiking neurons support fast cortical signaling

Fast spiking interneurons (FSINs) provide fast inhibition that synchronizes neuronal activity and is critical for cognitive function. Fast synchronization frequencies are evolutionary conserved in the expanded human neocortex, despite larger neuron-to-neuron distances that challenge fast input-output transfer functions of FSINs. Here, we test in human neurons from neurosurgery tissue which mechanistic specializations of human FSINs explain their fast-signaling properties in human cortex. With morphological reconstructions, multi-patch recordings, and biophysical modeling we find that despite three-fold longer dendritic path, human FSINs maintain fast inhibition between connected pyramidal neurons through several mechanisms: stronger synapse strength of excitatory inputs, larger dendrite diameter with reduced complexity, faster AP initiation, and faster and larger inhibitory output, while Na+ current activation/inactivation properties are similar. These adaptations underlie short input-output delays in fast inhibition of human pyramidal neurons through FSINs, explaining how cortical synchronization frequencies are conserved despite expanded and sparse network topology of human cortex. Teaser/one-sentence summarySpecializations of fast spiking human neurons ensure fast signaling in human cortex.

neuroscience↗

bioRxiv2022

Signature morpho-electric properties of diverse GABAergic interneurons in the human neocortex

Human cortical interneurons have been challenging to study due to high diversity and lack of mature brain tissue platforms and genetic targeting tools. We employed rapid GABAergic neuron viral labeling plus unbiased Patch-seq sampling in brain slices to define the signature morpho-electric properties of GABAergic neurons in the human neocortex. Viral targeting greatly facilitated sampling of the SST subclass, including primate specialized double bouquet cells which mapped to two SST transcriptomic types. Multimodal analysis uncovered an SST neuron type with properties inconsistent with original subclass assignment; we instead propose reclassification into PVALB subclass. Our findings provide novel insights about functional properties of human cortical GABAergic neuron subclasses and types and highlight the essential role of multimodal annotation for refinement of emerging transcriptomic cell type taxonomies. One Sentence SummaryViral genetic labeling of GABAergic neurons in human ex vivo brain slices paired with Patch-seq recording yields an in-depth functional annotation of human cortical interneuron subclasses and types and highlights the essential role of multimodal functional annotation for refinement of emerging transcriptomic cell type taxonomies.

neuroscience↗

bioRxiv2022

Morpho-electric and transcriptomic divergence of the layer 1 interneuron repertoire in human versus mouse neocortex

Neocortical layer 1 (L1) is a site of convergence between pyramidal neuron dendrites and feedback axons where local inhibitory signaling can profoundly shape cortical processing. Evolutionary expansion of human neocortex is marked by distinctive pyramidal neuron types with extensive branching in L1, but whether L1 interneurons are similarly diverse is underexplored. Using patch-seq recordings from human neurosurgically resected tissues, we identified four transcriptomically defined subclasses, unique subtypes within those subclasses and additional types with no mouse L1 homologue. Compared with mouse, human subclasses were more strongly distinct from each other across all modalities. Accompanied by higher neuron density and more variable cell sizes compared with mouse, these findings suggest L1 is an evolutionary hotspot, reflecting the increasing demands of regulating the expanding human neocortical circuit. One Sentence SummaryUsing transcriptomics and morpho-electric analyses, we describe innovations in human neocortical layer 1 interneurons.

neuroscience↗

bioRxiv2022

Proximity of astrocyte leaflets to the synapse determines memory strength

SummaryAstrocyte distal processes, known as leaflets or perisynaptic astrocyte processes (PAPs), fine-tune synaptic activity by clearing neurotransmitters and limiting extrasynaptic glutamate diffusion. While learning and memory depends on orchestrated synaptic activity of neuronal ensembles within the hippocampus, it is becoming increasingly evident that astrocytes residing in the environment of these synapses play a central role in shaping memories. However, how astroglial synaptic coverage contributes to mnemonic processing remains largely unknown. Here, we targeted astrocyte leaflet structure in vivo by depleting Ezrin, an integral leaflet-structural protein, in astrocytes of the adult hippocampal CA1 using a CRISPR-Cas9 genetic approach. This resulted in significantly smaller astrocyte territories and reduced astroglial synaptic coverage. In addition, using genetically encoded glutamate sensors and whole-cell patch-clamp recordings from pyramidal neurons, we found that Ezrin deletion and the resultant manipulation of leaflet structure boosted extrasynaptic glutamate diffusion and NMDA-receptor activation. Importantly, these cellular phenotypes translated to enhanced fear memory expression that was accompanied by increased activation of CA1 pyramidal neurons in the days after learning occurred. We show that Ezrin is critical for astrocyte morphology as well as for adult hippocampal synapse integrity and function. Our data show that astrocyte leaflet structure gates memory strength by regulating glutamate spillover in the vicinity of memory-related synaptic activity.

neuroscience↗

bioRxiv2021

Role of anterior insula cortex in context-induced relapse of nicotine-seeking

Tobacco use is the leading cause of preventable death worldwide, and relapse during abstinence remains the key barrier to successful treatment of tobacco addiction. During abstinence, environmental contexts associated with nicotine use can induce craving and contribute to relapse. The insular cortex (IC) is thought to be a critical substrate of nicotine addiction and relapse. However, its specific role in context-induced relapse of nicotine-seeking is not fully known. In this study, we report a novel rodent model of context-induced relapse to nicotine-seeking after punishment-imposed abstinence, which models self-imposed abstinence through increasing negative consequences of excessive drug use. Using the neuronal activity marker Fos we find that the anterior (aIC), but not the middle or posterior IC, shows increased activity during context-induced relapse. Combining Fos with retrograde labelling of aIC inputs, we show projections to aIC from contralateral aIC and basolateral amygdala exhibit increased activity during context-induced relapse. Next, we used fiber photometry in aIC and observed phasic increases in aIC activity around nicotine-seeking responses during self-administration, punishment, and the context-induced relapse tests. Next, we used chemogenetic inhibition in both male and female rats to determine whether activity in aIC is necessary for context-induced relapse. We found that chemogenetic inhibition of aIC decreased context-induced nicotine-seeking after either punishment- or extinction-imposed abstinence. These findings highlight the critical role nicotine-associated contexts play in promoting relapse, and they show that aIC activity is critical for this context-induced relapse following both punishment and extinction imposed abstinence.

neuroscience↗

bioRxiv2018

Prefrontal cortical ChAT-VIP interneurons provide local excitation by cholinergic synaptic transmission and control attention

Neocortical choline acetyltransferase (ChAT)-expressing interneurons are a subclass of vasoactive intestinal peptide (ChAT-VIP) neurons of which circuit and behavioural function are unknown. It has also not been addressed whether these neurons release both neurotransmitters acetylcholine (ACh) and GABA. Here, we find that in the medial prefrontal cortex (mPFC), ChAT-VIP neurons directly excite interneurons in layers (L)1-3 as well as pyramidal neurons in L2/3 and L6 by fast cholinergic transmission. Dual recordings of presynaptic ChAT-VIP neurons and postsynaptic L1 interneurons show fast nicotinic receptor currents strictly time-locked to single presynaptic action potentials. A fraction (10-20%) of postsynaptic neurons that received cholinergic input from ChAT-VIP interneurons also received GABAergic input from these neurons. In contrast to regular VIP interneurons, ChAT-VIP neurons did not disinhibit pyramidal neurons, but instead depolarized fast spiking and low threshold spiking interneurons. Finally, we find that ChAT-VIP neurons control attention behaviour distinctly from basal forebrain ACh inputs to mPFC. Our findings show that ChAT-VIP neurons are a local source of cortical ACh, that directly excite pyramidal and interneurons throughout cortical layers.

neuroscience↗