Biology subjects

Henny, P.

Publications and source records attributed to Henny, P..

4 recordsLinked to original sources

bioRxiv2026

A VTA-pontine GABA pathway biases backward locomotion via local and distal inhibition

Locomotor direction in mammals is implemented by descending circuits, yet how midbrain selection systems bias directional motor output remains unclear. Here we define a projection-defined inhibitory pathway from the ventral tegmental area to the oral pontine reticular nucleus (VTAPnO) whose activation is sufficient to drive backward locomotion. These TH- VTA neurons form monosynaptic GABAA synapses locally while projecting to PnO, establishing a dual local-projection inhibitory architecture. Somatic activation reliably induced backward locomotion, and selective stimulation of VTAPnO terminals reproduced the effect. Pathway recruitment produced a rapid transient increase in dopaminergic single-unit activity and frequency-dependent increases in dopaminergic population calcium signals in awake mice. During forced locomotion, chronically recorded VTAPnO neurons were preferentially engaged during reverse compared to forward rotations. Together, these findings reveal a projection-defined midbrain pathway that biases locomotor direction through coordinated local inhibition and distal engagement of a brainstem premotor node.

neuroscience↗

bioRxiv2023

Applying the area fraction fractionator (AFF) probe for total volume estimations of somatic, dendritic and axonal domains of the nigrostriatal dopaminergic system in a murine model

Using the nigrostriatal dopaminergic system as a case example, we describe a protocol based on Cavalieris principle to estimate the total volume of its somatic, nuclear, dendritic and axonal domains in the adult mouse. This protocol requires serial section analysis, a confocal laser scanning microscope (CLSM), and a stereological software combining the serial section manager (SSM) tool and the area fraction fractionator (AFF) probe. The protocol consists of the following steps: 1) systematic random sampling (SRS) of sites across sections for relevant regions of interest (ROI), which in this study included the substantia nigra pars compacta (SNc) and pars reticulata (SNr), the nigrostriatal tract, and the caudate-putamen complex (CP), 2) high resolution image acquisition of all SRS sites within and across sections, 3) loading of images on the previously defined SRS sites, 4) marking of all cellular structures of interest (cSOI) in the images, including perikarya and cell nuclei, dendrites, axonal segments and varicosities, using Cavalieris point-counting grids, and 5) estimation of cSOI total volume using the estimated area of each cSOI in every brain section, and the distance between sections. The added volume for all cSOI comprising the nigrostriatal dopaminergic system, in this murine model is around 0.37 mm3, with approximately 5% corresponding to perikarya and cell nuclei, 10% to neuropil/dendrites in substantia nigra, and 85% to axonal segments and varicosities within the CP. The use of a simple quantitative approach to assess the global state of a system may allow quantification of compartment-specific changes that may accompany neurodegenerative processes.

neuroscience↗

bioRxiv2022

Geometrical factors determining dendritic domain intersection between neurons: a modeling study

Overlap between dendritic trees of neighboring neurons is a feature of nervous systems. Overlap allows neurons to share common afferences and defines the topography of the circuit they belong to. Proximity is also a requirement for dendritic communication, including dendro-dendritic synaptic contacts. We simulated overlap dynamics between pairs of ventral tegmental area dopamine neurons, a population characterized by diverse and extensive dendritic domains. Using each neurons 3D convex hull (CH) as a proxy for dendritic domain size and shape, we examined intersection versus cell-to-cell distance curves for 210 pairs of neurons, and found that decay dynamics were diverse and complex, indicating that intersection between real dendritic domains does not comply with spherical or isotropic shape assumptions. We re-examined intersection dynamics for the same 210 pairs, but this time with either: a) a normalized volume corresponding to the average volume of all CHs, b) normalized shapes, using an average CH shape, or CHs from neurons exhibiting average dendritic distribution, isotropy or morphology, or c) a normalized cell body position, which we artificially placed in each CHs centroid. All three interventions significantly increased pair intersection and simplified decay dynamics, yet shape normalization had the strongest influence. Critically, shape uniformity was also the most relevant factor for increased dendritic domain pair intersection using the neurons original brain position and distances. We applied this experimental approach to other populations using reconstructions from neuromorpho.org database and found that shape and intersection dynamics were cell-type dependent. We conclude that intersection between neurons is not only maximized by proximity, but that individual-specific dendritic domain geometries have a profound impact too. The results predict that one biological solution for circuits requiring selective connectivity is to exhibit greater heterogeneity in size, cell body location, and especially shape, among their constituent neuronal elements.

neuroscience↗

bioRxiv2021

Organization of the catecholaminergic system in the short-lived fish Nothobranchius furzeri

The catecholaminergic system has received much attention based on its regulatory role in a wide range of brain functions and its relevance in aging and neurodegenerative diseases. In the present study, we analyzed the neuroanatomical distribution of catecholaminergic neurons based on tyrosine hydroxylase (TH) immunoreactivity in the brain of adult Nothobranchius furzeri. In the telencephalon, numerous TH+ neurons were observed in the olfactory bulbs and the ventral telencephalic area, arranged as strips extending through the rostrocaudal axis. We found the largest TH+ groups in the diencephalon at the preoptic region level, the ventral thalamus, the pretectal region, the posterior tuberculum, and the caudal hypothalamus. In the dorsal mesencephalic tegmentum, we identified a particular catecholaminergic group. The rostral rhombencephalon housed TH+ cells in the locus coeruleus and the medulla oblongata, distributing in a region dorsal to the inferior reticular formation, the vagal lobe, and the area postrema. Finally, scattered TH+ neurons were present in the ventral spinal cord and the retina. From a comparative perspective, the overall organization of catecholaminergic neurons is consistent with the general pattern reported for other teleosts. However, Nothobranchius furzeri shows some particular features, including the presence of catecholaminergic cells in the midbrain. This work provides a detailed neuroanatomical map of the catecholaminergic system of Nothobranchius furzeri, a powerful aging model, also contributing to the phylogenetic understanding of one of the most ancient neurochemical systems.

neuroscience↗