Electrophysiologically distinct bed nucleus of the stria terminalis projections to the ventral tegmental area in mice

Abstract

The bed nucleus of the stria terminalis (BNST) is a highly heterogeneous limbic forebrain structure that serves as a relay connecting autonomic, neuroendocrine and behavioral function. It can be divided into over 16 individual subregions with distinct neuronal subpopulations based on receptors, transmitters, and neuropeptides. Specifically, the BNST projection to the ventral tegmental area (VTA), the dopamine hub of the brain, has been shown to have a crucial role in the stress response. However, in mice there is a lack of unbiased data on the functional diversity of this sub-population which serves as an upstream input to the VTA. The dopaminergic neurons in the VTA modify their ion channel activity and intrinsic membrane properties to adapt to stress in part from inputs from BNST projections. Therefore, we aimed to perform a multi-component characterization of the functional diversity of the BNST-VTA pathway. We studied the passive and active electrophysiological properties of virally identified population of BNST neurons that project to the VTA. We used a comprehensive series of in vitro recordings of electrophysiological variables and performed hierarchical clustering to determine the functional diversity of the projection neurons in the BNST-VTA pathway. Our study revealed four subpopulations in the BNST-VTA pathway, all of which differ in their activation profiles and likely have distinct inputs and function in the VTA. Our results will help resolve the discord in interpretation of the various roles of this electrophysiologically diverse projection and builds a foundation for understanding how the different neuronal types integrate signals.

Chronic alcohol consumption alters sex-dependent BNST neuron function in rhesus macaques

“…4 L). Thus, time to hyperpolarization plateau was a better current clamp correlate of I h magnitude than voltage sag, suggesting that other significant conductances regulating membrane potential are at play in rhesus BNST neurons that may compete with those mediated by HCN channels upon hyperpolarization, an idea suggested previously for mouse BNST neurons ( Miura et al, 2022 ). Altogether, these excitability data provide converging evidence that increased excitability in response to depolarization in EtOH M compared to CON M was driven primarily by voltage-gated channel function regulating resting membrane potential.…”

“…BNST neurons in rodents have previously been categorized into multiple types based on voltage responses to hyperpolarizing and depolarizing current injection steps, including inward rectification and voltage sag, the latter of which has been used as a proxy measure for HCN channel-mediated I h , and action potential firing pattern (Type I: large voltage sag, little inward rectification, persistent firing, and no I t ; Type II: little/no voltage sag or inward rectification, large I t , burst firing, and/or rebound firing; Type III: large inward rectification, little/no voltage sag or I t ) ( Hammack et al, 2007 ; Daniel et al, 2017 ). While these categories were determined in male rats and segregate BNST neurons into equal thirds in that subject population, both male mouse and male monkey BNST neurons have been shown to be less distinguishable based on the combination of these measures ( Silberman et al, 2013 ; Daniel et al, 2017 ; Miura et al, 2022 ). This is, in part, due to the presence of additional features in these cells, such as irregular firing and a lack of voltage sag in most neurons (which we also found here).…”

“…Further, in male mice, the use of these categories has not proven to be useful in distinguishing specific cell types of BNST projection populations. For example, both the CRF neuron and VTA-projecting neuron populations in the BNST of male mice have been shown to have all three Types, as well as a large proportion of neurons that fall into an “Other” category because they do not fit into the three Types ( Silberman et al, 2013 ; Miura et al, 2022 ). Here, the use of voltage clamp recordings (in the same cells in which we performed current clamp recordings) to more directly assess I h showed than many cells in CON M monkeys displayed a large I h in voltage clamps even though they displayed almost no voltage sag in current clamp.…”

“…Thus, while there was a large effect of EtOH on decreasing I h , this effect was not detected when using voltage sag as a proxy measure. Similarly, a comprehensive study in male mice that also measured I h in voltage clamp and voltage sag in current clamp showed that these measures were not related to one another, finding that VTA-projecting BNST neurons displayed any possible combination of these (large I h and large sag, large I h but no sag, no/little I h but large sag, and no I h or sag) ( Miura et al, 2022 ). Altogether, these data suggest that voltage sag is not a suitable proxy measure for I h in monkey (and perhaps mouse) BNST neurons, likely because there are other conductances activated at hyperpolarized potentials that interfere with this as a measure or contribute to its presence, as well as the ability to detect effects, such as alcohol-mediated plasticity in our study.…”

The neurophysiological basis of stress and anxiety - comparing neuronal diversity in the bed nucleus of the stria terminalis (BNST) across species

“…BNST connections to and from these autonomic brain stem centers have also been found in both rodents and humans ( Dong et al, 2001a ; Hofmann and Straube, 2019 ; Sun et al, 2023 ), with evidence still lacking in non-human primates. As the BNST plays an important role in reward and addiction ( Volkow et al, 2019 ), its connection to the midbrain ventral tegmental area (VTA) and NAc and the dopamine reward system has also been extensively studied in rodents, primate and humans ( Kudo et al, 2012 ; Kaufling et al, 2017 ; Miura et al, 2022 ). Dopaminergic VTA neurons project to the medial prefrontal cortex (mPFC) and the NAc which in resting state are thought to be mostly silent due to inhibition from gamma-aminobutyric acid (GABA-)ergic inputs from the ventral pallidum ( Kudo et al, 2012 ).…”