Like sisters but not twins - vasopressin and oxytocin excite BNST neurons via cell type-specific expression of oxytocin receptor to reduce anxious arousal

Interoceptive signals dynamically interact with the environment to shape appropriate defensive behaviors. Hypothalamic hormones arginine-vasopressin (AVP) and oxytocin (OT) regulate physiological states, including water and electrolyte balance, circadian rhythmicity, and defensive behaviors. Both AVP and OT neurons project to dorsolateral bed nucleus of stria terminalis (BNSTDL), which expresses oxytocin receptors (OTR) and vasopressin receptors and mediates fear responses. However, understanding the integrated role of neurohypophysial hormones is complicated by the cross-reactivity of AVP and OT and their mutual receptor promiscuity. Here, we provide evidence that the effects of neurohypophysial hormones on BNST excitability are driven by input specificity and cell type-specific receptor selectivity. We show that OTR-expressing BNSTDL neurons, excited by hypothalamic OT and AVP inputs via OTR, play a major role in regulating BNSTDL excitability, overcoming threat avoidance, and reducing threat-elicited anxious arousal. Therefore, OTR-BNSTDL neurons are perfectly suited to drive the dynamic interactions balancing external threat risk and physiological needs. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=143 SRC="FIGDIR/small/611656v2_ufig1.gif" ALT="Figure 1"> View larger version (27K): org.highwire.dtl.DTLVardef@2c800forg.highwire.dtl.DTLVardef@18b5cfaorg.highwire.dtl.DTLVardef@85324aorg.highwire.dtl.DTLVardef@a8bb6b_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LIExogenous and light-evoked vasopressin (AVP) peptide excites neurons of the bed nucleus of the stria terminalis (BNST) via oxytocin receptor (OTR) in male rats C_LIO_LIAVP excites OTR- and Corticotropin-releasing factor (CRF)-expressing neurons, most of which are classified as Type III neurons of the BNST C_LIO_LIOTR-expressing BNST neurons increase exploration of open spaces and reduce anxious arousal in fear-potentiated startle in male rats C_LIO_LIThe dorsolateral BNST receives vasopressinergic inputs from suprachiasmatic, supraoptic, and paraventricular nuclei of the hypothalamus C_LIO_LIInternal signal-sensitive hypothalamic inputs directly impact BNST excitability via OTR to balance interoceptive signals and defensive behaviors C_LI