Molecular and anatomical characterization of parabrachial neurons and their axonal projections

Abstract

The parabrachial nucleus (PBN) is a major hub that receives sensory information from both internal and external environments. Specific populations of PBN neurons are involved in behaviors including food and water intake, nociceptive responses, breathing regulation, as well as learning and responding appropriately to threatening stimuli. However, it is unclear how many PBN neuron populations exist and how different behaviors may be encoded by unique signaling molecules or receptors. Here we provide a repository of data on the molecular identity, spatial location, and projection patterns of dozens of PBN neuron subclusters. Using single-cell RNA sequencing, we identified 21 subclusters of neurons in the PBN and neighboring regions. Multiplexed in situ hybridization showed many of these subclusters are enriched within specific PBN subregions with scattered cells in several other regions. We also provide detailed visualization of the axonal projections from 21 Cre-driver lines of mice. These results are all publicly available for download and provide a foundation for further interrogation of PBN functions and connections.

Parabrachial tachykinin1-expressing neurons involved in state-dependent breathing control

“…Non-cell type specific electrical or chemical stimulations of the PBN elicit varied effects on breathing, capable of producing either increases or decreases in respiratory activity 60 , 61 , suggesting there are multiple subpopulations of PBN neurons with distinct respiratory functions. Yet, the respiratory roles of specific transcriptionally defined PBN neuronal subtypes are not well defined compared to those of the preBötC, and targeted manipulations have primarily involved neurons that express the mu opioid receptor (MOR), encoded by Oprm1 17 , 51 , which is widely expressed across many PBN neurons in its lateral, medial, and Kölliker-Fuse (KF) subdivisions 48 , 62 , 63 .…”

“…S2a ). Thus, despite Tac1 and CGRP being co-expressed in many neurons of the lateral PBN (see above and 48 ), their activation elicits opposing effects on breathing in the awake state, with Tac1 neurons promoting rapid breathing patterns and CGRP neurons suppressing them.…”

“…However, defining its specific contributions to rhythm generation and modulation has been difficult. This is due, in part, to the large variety of cell types in this region that are diverse in their gene expression, axonal projections, and functions 43 – 48 , which has hindered interpretation of non-cell-type specific manipulation experiments. Indeed, the PBN is considered an integrative hub for many behaviors, affective states, and autonomic responses 49 , 50 and contains ~12 transcriptionally distinct neuronal populations as defined by RNA-Sequencing 48 .…”

“…This is due, in part, to the large variety of cell types in this region that are diverse in their gene expression, axonal projections, and functions 43 – 48 , which has hindered interpretation of non-cell-type specific manipulation experiments. Indeed, the PBN is considered an integrative hub for many behaviors, affective states, and autonomic responses 49 , 50 and contains ~12 transcriptionally distinct neuronal populations as defined by RNA-Sequencing 48 . However, modern neuroscience approaches that allow manipulations of transcriptionally and anatomically defined cell-types have only recently begun to be applied to unravel how restricted PBN populations may regulate breathing 17 , 51 .…”

A deep-learning driven investigation of circuit basis for reflexive hypersensitivity to pain

“…lPBN and lPAG in turn project downstream to the spinally projecting pro-nociceptive MdD, and antinociceptive rostral ventromedial medulla (RVM), respectively [26], [11]. Neuropeptide genes and their receptors, such as Tachykinin1 (Tac1) and its receptor tachykinin receptor 1 (Tacr1), are enriched in pro-nociceptive brain areas such as the lPBN, lPAG, and MDd [48], [24]. Chemogenetic and optogenetic manipulations of Tac1 and Tacr1 expressing neuronal populations in the lPBN and Tac1 in the MdD promotes jumping responses in the hot-plate test [13].…”