Sensory innervation of the anterior eye segment in rats: aretrograde tracing study

This study aimed to investigate the sensory innervation of the anterior eye segment in rats by retrograde tracing with 1,1-dioleyl-3,3,3,3-tetrameth-ylindocarbocyanine,4-chlorobenesulfonate(FAST Dil)injected into the anterior chamber.The sensory innervation of distinct elements of the anterior segment of the rat’s eye,i.e.the cornea,ciliary body,iris,and trabecular meshwork,were studied by retrograde tracing using FAST Dil as a tracer.FAST Dil was injected into the anterior chambers of the rat’s eyes.The animals were sacrificed at different time points,i.e.,2,3,4,and 5 days after the injection.FAST Dil localization in trigeminal ganglions was studied with afluorescent microscope.Two days after FAST Dil injection into the anterior chambers,the cornea,the ciliary body,the iris,and the trabecular meshwork were heavily labeled.Neurons in the ipsilateral trigeminal ganglion were also consistently labeled.The number of labeled cells increased over time until 4 days after FAST Dil injection.FAST Dil-labeled neurons could be divided into two parts.Most of the Dil-labeled neurons were concentrated in a sharp,longitudinal,spindle-like stripe,located in the dorso-medial side of the trigeminal ganglion,approximately two thirds of the dorsal portion.The other part of Dil-labeled neurons scattered laterally to the stripe,but just in one third of the dorsal region.Thus,with our preliminary results,we conclude that the primary afferent sensory neurons innervating the rat’s anterior eye segments aggregate in the dorso-medial part of the ipsilateral trigeminal ganglion.It is feasible to identify them using retrograde tracing with FAST Dil anterior chamber injection.

The Double Projecting Neuron of the Cat Spinal Dorsal Horn——A Study with Double Retrograde Fluorescent Tracing Technique

The new double projecting neurons were found in the cat spinal dorsal horn by the double retrograde fluorescent tracing technique.Fast Blue(FB)was injected into unilateral dorsal column nucleus(DCN)of adult cats anesthetized with pentobarbital.Nuclear Yellow(NY)was injected ipsilaterally into the lateral cervical nucleus(LCN)8-9 days later.After an additional 18-30 hrs.

A"messenger zone hypothesis"based on the visual three-dimensional spatial distribution of motoneurons innervating deep limb muscles

Coordinated contraction of skeletal muscles relies on selective connections between the muscles and multiple classes of the spinal motoneuro ns.Howeve r,current research on the spatial location of the spinal motoneurons innervating differe nt muscles is limited.In this study,we investigated the spatial distribution and relative position of different motoneurons that control the deep muscles of the mouse hindlimbs,which were innervated by the obturator nerve,femoral nerve,inferior gluteal nerve,deep pe roneal nerve,and tibial nerve.Locations were visualized by combining a multiplex retrograde tracking technique compatible with three-dimensional imaging of solvent-cleared o rgans(3DISCO)and 3-D imaging technology based on lightsheet fluorescence microscopy(LSFM).Additionally,we propose the hypothesis that"messenger zones"exist as interlaced areas between the motoneuron pools that dominate the synergistic or antagonist muscle groups.We hypothesize that these interlaced neurons may participate in muscle coordination as messenger neurons.Analysis revealed the precise mutual positional relationships among the many motoneurons that innervate different deep muscles of the mouse.Not only do these findings update and supplement our knowledge regarding the overall spatial layout of spinal motoneurons that control mouse limb muscles,but they also provide insights into the mechanisms through which muscle activity is coordinated and the architecture of motor circuits.

Whole-Brain Map of Long-Range Monosynaptic Inputs to Different Cell Types in the Amygdala of the Mouse

The amygdala,which is involved in various behaviors and emotions,is reported to connect with the whole brain.However,the long-range inputs of distinct cell types have not yet been defined.Here,we used a retrograde trans-synaptic rabies virus to generate a whole-brain map of inputs to the main cell types in the mouse amygdala.We identified 37 individual regions that projected to neurons expressing vesicular glutamate transporter 2,78 regions to parvalbumin-expressing neurons,104 regions to neurons expressing protein kinase C-δ,and 89 regions to somatostatin-expressing neurons.The amygdala received massive projections from the isocortex and striatum.Several nuclei,such as the caudate-putamen and the CA1 field of the hippocampus,exhibited input preferences to different cell types in the amygdala.Notably,we identified several novel input areas,including the substantia innominata and zona incerta.These findings provide anatomical evidence to help understand the precise connections and diverse functions of the amygdala.

Sexual Dimorphism of Inputs to the Lateral Habenula in Mice

The lateral habenula(LHb),which is a critical neuroanatomical hub and a regulator of midbrain monoaminergic centers,is activated by events resulting in negative valence and contributes to the expression of both appetitive and aversive behaviors.However,whole-brain cell-type-specific monosynaptic inputs to the LHb in both sexes remain incompletely elucidated.In this study,we used viral tracing combined with in situ hybridization targeting vesicular glutamate transporter 2(vGlut2)and glutamic acid decarboxylase 2(Gad2)to generate a comprehensive whole-brain atlas of inputs to glutamatergic andγ-aminobutyric acid(GABA)ergic neurons in the LHb.We found>30 ipsilateral and contralateral brain regions that projected to the LHb.Of these,there were significantly more monosynaptic LHb-projecting neurons from the lateral septum,anterior hypothalamus,dorsomedial hypothalamus,and ventromedial hypothalamus in females than in males.More interestingly,we found a stronger GABAergic projection from the medial septum to the LHb in males than in females.Our results reveal a comprehensive connectivity atlas of glutamatergic and GABAergic inputs to the LHb in both sexes,which may facilitate a better understanding of sexual dimorphism in physiological and pathological brain functions.