Biology subjects

Blasiak, A.

Publications and source records attributed to Blasiak, A..

6 recordsLinked to original sources

bioRxiv2024

Early-life adversity alters adult nucleus incertus neurons: implications for neuronal mechanisms of increased stress and compulsive behavior vulnerability

BACKGROUNDEarly-life stress (ELS) arising from physical and emotional abuse disrupts normal brain development and impairs hypothalamic-pituitary-adrenal axis function, increasing the risk of psychopathological disorders and compulsive behaviors in adulthood. However, the underlying neural mechanisms remain unclear. The brainstem nucleus incertus (NI) is a highly stress-sensitive locus, involved in behavioral activation and stress-induced reward (food/alcohol) seeking, but its sensitivity to ELS remains unexplored. METHODSWe used neonatal maternal separation stress in rats as a model for ELS and examined its impact on stress-related mRNA and neuropeptide expression in the NI, using fluorescent in situ hybridization and immunohistochemistry, respectively. Using whole-cell, patch-clamp recordings we determined the influence of ELS on the synaptic activity, excitability, and electrophysiological properties of NI neurons. Using c-Fos protein expression we also assessed the impact of ELS on the sensitivity of NI neurons to acute restraint stress in adulthood. RESULTSELS weakened the acute stress responsiveness of NI neurons, and caused dendritic shrinkage, impaired synaptic transmission and altered electrophysiological properties of NI neurons in a cell-type-specific manner. Additionally, ELS increased the expression of mRNA encoding corticotropin-releasing hormone receptor type 1 and the nerve-growth factor receptor, TrkA in adult NI. CONCLUSIONSThe multiple, cell-type specific changes in the expression of neuropeptides and molecules associated with stress and substance abuse in the NI, as well as impairments in NI neuron morphology and electrophysiology caused by early-life stress and observed in the adult brain, may contribute to the increased susceptibility to stress and compulsive behaviors observed in individuals with a history of ELS.

neuroscience↗

bioRxiv2024

Oxytocin facilitates social behavior of female rats via selective modulation of interneurons in the medial prefrontal cortex

The hypothalamic neuropeptide oxytocin is best known for its prosocial behavioral effects. However, the precise anatomical and cellular targets for oxytocin in the cortex during social behavior remain elusive. Here we show that oxytocin neurons project directly to the medial prefrontal cortex where evoked axonal oxytocin release facilitates social behaviors in adult female rats. In conjunction, we report that local oxytocin receptor-expressing (OTR+) cells are predominantly interneurons, whose activation promotes social interaction. Notably, this prosocial effect persists even under physiological challenge (hunger), pointing to a dedicated prosocial circuit capable of overriding primary survival drives. We further demonstrate that activation of these OTR+ interneurons inhibits principal cells specifically projecting to the basolateral amygdala, thus providing a putative mechanism of selective oxytocin action in this sociability-promoting cortical network.

neuroscience↗

bioRxiv2023

Unveiling a Novel Memory Center in Humans: Neurochemical Identification of the Nucleus Incertus, a Key Pontine Locus Implicated in Stress and Neuropathology

BackgroundThe nucleus incertus (NI) was originally described by Streeter in 1903, as a midline region in the floor of the fourth ventricle (4V) of the human brain with an unknown function. More than a century later, the neuroanatomy of the NI including its forebrain target regions has been described in lower vertebrates, but not in humans. Therefore, we examined the neurochemical anatomy of the human NI using several markers, including the neuropeptide, relaxin-3 (RLN3), and began to explore the distribution of the NI-related RLN3 innervation of the hippocampus. MethodsHistochemical staining of serial, coronal sections (30 {micro}m) of control human postmortem pons was conducted to reveal the presence of the NI by detection of immunoreactivity (IR) for the neuronal marker, microtubule-associated protein-2 (MAP2), two markers present in rat NI, glutamic acid dehydrogenase (GAD)-65/67 and corticotrophin releasing hormone receptor 1 (CRHR1), and RLN3, which is highly expressed in a major population of NI neurons in diverse species. RLN3 and vesicular GABA transporter 1 (vGAT1) mRNA was detected by multiplex, fluorescence in situ hybridization. Postmortem pons sections containing the NI from an Alzheimers disease (AD) case were immunostained for phosphorylated-tau (AT8 antibody), to explore potential relevance to neurodegenerative diseases. Lastly, sections of human hippocampus were stained to detect RLN3-IR and somatostatin (SST)-IR, as SST is expressed in interneurons targeted by RLN3 projections in rodents. ResultsIn the dorsal, anterior-medial region of the human pons, neurons containing RLN3- and MAP2-IR, and RLN3/vGAT1 mRNA-positive neurons were observed in an anatomical pattern consistent with that of the NI in other species. GAD65/67- and CRHR1-immunopositive neurons were also detected within this area. Furthermore, RLN3- and AT8-IR were co-localized within NI neurons of an AD subject. Lastly, RLN3-IR was detected in neurons within the CA1, CA2, CA3, and DG areas of the hippocampus, in the absence of RLN3 mRNA. In the DG, RLN3- and SST-IR were co-localized in a small population of neurons. ConclusionsAspects of the anatomy of the human NI are shared across species, including a population of RLN3-expressing neurons and a RLN3 innervation of the hippocampus. Accumulation of phosphorylated-tau in the NI suggests its possible involvement in AD pathology. Further characterization of the neurochemistry of the human NI will increase our understanding of its functional role in health and disease. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=75 SRC="FIGDIR/small/556922v1_ufig1.gif" ALT="Figure 1"> View larger version (24K): org.highwire.dtl.DTLVardef@f4c439org.highwire.dtl.DTLVardef@17e85f5org.highwire.dtl.DTLVardef@18ca7faorg.highwire.dtl.DTLVardef@168246c_HPS_FORMAT_FIGEXP M_FIG Graphical Abstract Created with BioRender.com C_FIG

neuroscience↗

bioRxiv2023

Dopamine receptor-expressing neurons are differently distributed throughout layers of the motor cortex to control dexterity

The motor cortex comprises the primary descending circuits for flexible control of voluntary movements and is critically involved in motor skill learning. Motor skill learning is impaired in patients with Parkinsons disease, but the precise mechanisms of motor control and skill learning are still not well understood. Here we have used transgenic mice, electrophysiology, in situ hybridization and neural tract-tracing methods to target genetically defined cell types expressing D1 and D2 dopamine receptors (D1+ and D2+, respectively) in the motor cortex. We observed that D1+ and D2+ neurons are organized in highly segregated, non-overlapping populations. Moreover, based on ex vivo patch-clamp recordings, we showed that D1+ and D2+ cells have distinct morphological and electrophysiological properties. Finally, we observed that chemogenetic inhibition of D2+, but not D1+ neurons, disrupts skilled forelimb reaching in adult mice. Overall, these results demonstrate that dopamine receptor-expressing cells in the motor cortex are highly segregated and play a specialized role in manual dexterity.

neuroscience↗

bioRxiv2023

Mitochondrial fitness influences neuronal excitability of dopaminergic neurons from patients with idiopathic form of Parkinson's disease

Parkinson disease is the second most common neurodegenerative disease defined by presence of Lewy bodies and the loss of dopaminergic neurons in the substantia nigra pars compacta (SNc). There are three types of PD - familial, early-onset and idiopathic. Idiopathic PD (IPD) accounts for approximately 90% of all PD cases. Mitochondrial dysfunction accompanies the pathogenesis of Parkinsons disease. Loss of mitochondrial function increases oxidative stress and calcium buffering, which in turn hinders the production of ATP and disrupts the functioning of dopaminergic neurons. The main barrier in PD research was the lack of proper human models to study the mechanisms of PD development and progression. Using induced pluripotent stem (iPS) cells we generated patient-specific dopaminergic neurons. We observed differences in the mitochondria fitness but not differences in mitochondria mass, morphology or membrane potential. Expression of OXPHOS mitochondrial complexes were lower in PD patients in comparison to control group what resulted in changes in mitochondria respiratory status. We observed also lower expression levels of Na+/K+-ATPase subunits and ATP-sensitive K+ (K-ATP) channel subunits. The lower oxygen consumption rate and extracellular acidification rate values were observed in dopaminergic progenitors and iPSC from PD patients compared to the control group. Importantly, observed decrease in the availability of ATP and in the energy consumption, as well as changes in acidification, may constitute contributing factors to the observed reduced neuronal excitability of PD patients dopaminergic neurons.

neuroscience↗

bioRxiv2020

Loss of mu and delta opioid receptors on neurons expressing dopamine receptor D1 has no effect on reward sensitivity

Opioid signaling controls the activity of the brains reward system. It is involved in signaling the hedonic effects of rewards and also has essential roles in reinforcement and motivational processes. Here, we focused on opioid signaling through mu and delta receptors on dopaminoceptive neurons and evaluated the role these receptors play in reward-driven behaviors. We generated a genetically modified mouse with selective double knockdown of mu and delta opioid receptors in neurons expressing dopamine receptor D1. Selective expression of the transgene was confirmed using immunostaining. Knockdown was validated by measuring the effects of selective opioid receptor agonists on neuronal membrane currents using whole-cell patch clamp recordings. We found that in the nucleus accumbens of control mice, the majority of dopamine receptor D1-expressing neurons were sensitive to a mu or delta opioid agonist. In mutant mice, the response to the delta receptor agonist was blocked, while the effects of the mu agonist were strongly attenuated. Behaviorally, the mice had no obvious impairments. The mutation did not affect sensitivity to the rewarding effects of morphine injections or social contact and had no effect on preference for sweet taste. Knockdown had a moderate effect on motor activity in some of the tests performed, but this effect did not reach statistical significance. Thus, we found that knocking down mu and delta receptors on dopamine receptor D1-expressing cells does not appreciably affect reward-driven behaviors. Highlights- It is well accepted that opioid signaling controls the brains reward system - We generated mutant mice with mu and delta receptor knockdown in D1 neurons - Knockdown made dopaminoceptive neurons insensitive to mu and delta opioid receptor agonists - The mutation did not cause obvious behavioral impairments - The loss of mu and delta receptors on D1 neurons does not affect reward sensitivity

neuroscience↗