Characterization of the relaxin family peptide receptor 3 system in the mouse bed nucleus of the stria terminalis

Abstract

The bed nucleus of the stria terminalis (BNST) is a critical node involved in stress and reward‐related behaviors. Relaxin family peptide receptor 3 (RXFP3) signaling in the BNST has been implicated in stress‐induced alcohol seeking behavior. However, the neurochemical phenotype and connectivity of BNST RXFP3‐expressing (RXFP3+) cells have yet to be elucidated. We interrogated the molecular signature and electrophysiological properties of BNST RXFP3+ neurons using a RXFP3‐Cre reporter mouse line. BNST RXFP3+ cells are circumscribed to the dorsal BNST (dBNST) and are neurochemically heterogeneous, comprising a mix of inhibitory and excitatory neurons. Immunohistochemistry revealed that ~48% of BNST RXFP3+ neurons are GABAergic, and a quarter of these co‐express the calcium‐binding protein, calbindin. A subset of BNST RXFP3+ cells (~41%) co‐express CaMKIIα, suggesting this subpopulation of BNST RXFP3+ neurons are excitatory. Corroborating this, RNAscope® revealed that ~35% of BNST RXFP3+ cells express vVGluT2 mRNA, indicating a subpopulation of RXFP3+ neurons are glutamatergic. RXFP3+ neurons show direct hyperpolarization to bath application of a selective RXFP3 agonist, RXFP3‐A2, while around 50% of cells were depolarised by exogenous corticotrophin releasing factor. In behaviorally naive mice the majority of RXFP3+ neurons were Type II cells exhibiting Ih and T type calcium mediated currents. However, chronic swim stress caused persistent plasticity, decreasing the proportion of neurons that express these channels. These studies are the first to characterize the BNST RXFP3 system in mouse and lay the foundation for future functional studies appraising the role of the murine BNST RXFP3 system in more complex behaviors.

RLN3/RXFP3 Signaling in the PVN Inhibits Magnocellular Neurons via M-like Current Activation and Contributes to Binge Eating Behavior

“…Although RXFP3 has been shown to modulate synaptic inputs to parvocellular PVN CRF neurons ( C. Zhang et al, 2017 ) and neurons of the bed nucleus of stria terminalis in mice ( Ch'ng et al, 2019 ), neither RLN3 nor a selective RXFP3 agonist influenced excitatory NMDA/AMPA or inhibitory GABA A receptor-mediated postsynaptic currents (spontaneous and miniature) recorded from PVN MNCs in our rat brain preparations. We therefore conclude that RLN3 inputs primarily act on postsynaptically located RXFP3 to modulate MNC activity in the rat.…”

Enhanced synaptic transmission in the extended amygdala and altered excitability in an extended amygdala to brainstem circuit in a Dravet syndrome mouse model

“…The plurality of these were Type I neurons (n=5/10 cells) but Type II (n=2/10 cells), Type III (n=1/10 cells) and other (n=2/10) are present. The fact that there is not a strict predominance of a single physiological type in those neurons projecting to the PBN is not unexpected as neither neuronal morphology, expression of neuropeptide markers, nor projection location has previously been shown to associate with a particular physiological sub-type (Ch'ng et al, 2019;Rodríguez-Sierra et al, 2013;Silberman et al, 2013). (Figure 5i-k).…”

Differential Level of RXFP3 Expression in Dopaminergic Neurons Within the Arcuate Nucleus, Dorsomedial Hypothalamus and Ventral Tegmental Area of RXFP3-Cre/tdTomato Mice

“…RXFP3-Cre/tdTomato double transgenic mice (heterozygous for each mutation) were bred by pairing separate homozygous RXFP3-Cre and Rosa26-tdTomato reporter strains, as described (Ch'ng et al, 2019). The RXFP3-Cre [Tg(Rxfp3-cre), RS38Gsat] strain was maintained on a mixed background of FVB/N and Crl:CD1 (ICR; obtained from MMRRC/Gensat, stock no.…”

“…The aim of this study was to determine whether RXFP3 is expressed by dopaminergic neurons within the ARC, DMH and VTA, to identify or exclude potential direct RXFP3-mediated effects on neurons in these areas. As a fully validated RXFP3 antibody is not yet available, transgenic RXFP3-Cre/tdTomato mice were used to visualize RXFP3-expressing neurons (Ch'ng et al, 2019). Histochemical detection of tdTomato fluorescence was combined with immunohistochemical detection of tyrosine hydroxylase (TH), an enzyme involved in the synthesis of catecholamines (Björklund and Dunnett, 2007), including dopamine (Daubner et al, 2011).…”