Barrington's nucleus: Neuroanatomic landscape of the mouse “pontine micturition center”

Abstract

Barrington’s nucleus (Bar) is thought to contain neurons that trigger voiding and thereby function as the “pontine micturition center.” Lacking detailed information on this region in mice, we examined gene and protein markers to characterize Bar and the neurons surrounding it. Like rats and cats, mice have an ovoid core of medium-sized Bar neurons located medial to the locus coeruleus (LC). Bar neurons express a GFP reporter for Vglut2, develop from a Math1/Atoh1 lineage, and exhibit immunoreactivity for NeuN. Many neurons in and around this core cluster express a reporter for corticotrophin-releasing hormone (BarCRH). Axons from BarCRH neurons project to the lumbosacral spinal cord and ramify extensively in two regions: the dorsal gray commissural and intermediolateral nuclei. BarCRH neurons have unexpectedly long dendrites, which may receive synaptic input from the cerebral cortex and other brain regions beyond the core afferents identified previously. Finally, at least five populations of neurons surround Bar: rostral-dorsomedial cholinergic neurons in the laterodorsal tegmental nucleus; lateral noradrenergic neurons in the LC; medial GABAergic neurons in the pontine central gray; ventromedial, small GABAergic neurons that express FoxP2; and dorsolateral glutamatergic neurons that express FoxP2 in the pLC and form a wedge dividing Bar from the dorsal LC. We discuss the implications of this new information for interpreting existing data and future experiments targeting BarCRH neurons and their synaptic afferents to study micturition and other pelvic functions.

Aldosterone-sensitive HSD2 neurons in mice

“…This FoxP2+ subpopulation is homologous to the population we named pre-LC in rats, where these neurons lie rostral to the LC. In mice, we abbreviate this population “pLC”; it includes FoxP2+ neurons receiving dense HSD2 axon terminals, flanking and streaking through the LC laterally into what is conventionally or otherwise defined as part of the medial PB, and runs medially between the LC and Barrington’s nucleus (Verstegen et al, 2017). We found only sparse axonal labeling inside Barrington’s nucleus, which is FoxP2-negative.…”

“…To construct the whole-brain map of axonal projections, we manually traced axons and boutons with NiDAB immunolabeling for dsRed (Syp-mCherry) in Adobe Illustrator, then overlaid the Nissl-counterstained, re-scanned images of each section, which aided in labeling and outlining a minimal set of landmarks at each level for neuroanatomical clarity. We used neuroanatomical terminology from the peer-reviewed scientific literature (Geerling and Loewy, 2006b; Shin et al, 2008; Geerling et al, 2010; Verstegen et al, 2017) and, for some well-established regions and neuron populations, from commercially-available mouse brain atlases (Dong, 2008; Franklin and Paxinos, 2013). We used Adobe Photoshop to import raw fluorescence (grayscale) data into color channels for multicolor combinations, crop bitmap images, and adjust brightness or contrast.…”

Cortical lesions causing loss of consciousness are anticorrelated with the dorsal brainstem

“…Answering this question in a definitive way is beyond the spatial resolution of imaging techniques such as fMRI, and is likely to benefit from ongoing work in animal models (Cho et al, ; Grandjean et al, ). This region of dorsal brainstem is composed of many different nuclei and neuronal subpopulations (Magoun, ; Verstegen, Vanderhorst, Gray, Zeidel, & Geerling, ; Wang & Morales, ). Some nuclei, like the locus coeruleus and parabrachial nucleus, primarily express excitatory neurotransmitters, promote arousal, and align well with the location of coma‐causing brainstem lesions (Fischer et al, ; Fuller et al, ; Magoun, ).…”

“…Some nuclei, like the locus coeruleus and parabrachial nucleus, primarily express excitatory neurotransmitters, promote arousal, and align well with the location of coma‐causing brainstem lesions (Fischer et al, ; Fuller et al, ; Magoun, ). Other neurons in this same area may actually suppress arousal or promote sleep, including interdigitating GABA and glycinergic neurons (Verstegen et al, , Wang & Morales, ), as well as serotonergic neurons within the dorsal raphe (Denoyer, Sallanon, Kitahama, Aubert, & Jouvet, ; Sakai, ). This latter finding may be particularly relevant to the current results, as the peak connection associated with LOC overlapped the dorsal raphe.…”

Laminar specific gene expression reveals differences in postnatal laminar maturation in mouse auditory, visual, and somatosensory cortex

“…The specificity was previously tested by interacting with heterologously expressed proteins and subsequent immunohistochemistry (Thompson et al, ). This antibody has been extensively used in immunofluorochemistry (Arellano, Guadiana, Breunig, Rakic, & Sarkisian, ; Ebisu, Iwai‐Takekoshi, Fujita‐Jimbo, Momoi, & Kawasaki, ; Ganz et al, ; Iwai et al, ; Verstegen, Vanderhorst, Gray, Zeidel, & Geerling, ). The labeled neurons were distributed to the deep layer of mouse neocortex and represent a major population of layer 6 neurons (Ferland et al, ; Iwai et al, ).…”