TheFoxb1‐expressing neurons of the ventrolateral hypothalamic parvafox nucleus project to defensive circuits

Abstract

The parvafox nucleus is an elongated structure that is lodged within the ventrolateral hypothalamus and lies along the optic tract. It comprises axially located parvalbumin (Parv)-positive neurons and a peripheral cuff of Foxb1-expressing ones. In the present study, injections of Cre-dependent adenoviral constructs were targeted to the ventrolateral hypothalamus of Foxb1/Cre mice to label specifically and map the efferent connections of the Foxb1-expressing subpopulation of neurons of the parvafox nucleus. These neurons project more widely than do the Parv-positive ones and implicate a part of the axons known to emanate from the lateral hypothalamus. High labeling densities were found in the dorsolateral and the upper lateral portion of the periaqueductal gray (PAG), the Su3 and PV2 nuclei of the ventrolateral PAG, the cuneiform nucleus, the mesencephalic reticular formation, and the superior colliculus. Intermediate densities of terminals were encountered in the septum, bed nucleus of the stria terminalis, substantia innominata, various thalamic and hypothalamic nuclei, pedunculopontine nucleus, Barrington's nucleus, retrofacial nucleus, and retroambigual nucleus. Scattered terminals were observed in the olfactory bulbs, the prefrontal cortex and the lamina X of the cervical spinal cord. Because the terminals were demonstrated to express the glutamate transporter VGlut2, the projections are presumed to be excitatory. A common denominator of the main target sites of the Foxb1-positive axons of the parvafox nucleus appears to be an involvement in the defensive reactions to life-threatening situations. The hypothalamic parvafox nucleus may contribute to the autonomic manifestations that accompany the expression of emotions. J. Comp. Neurol. 524:2955-2981, 2016. © 2016 Wiley Periodicals, Inc.

Reconciling cognitive and affective neuroscience perspectives on the brain basis of emotional experience

“…For instance, the DBS mapping of positively-valenced "rat laughter" sites (Burgdorf et al, 2007) has helped illuminate the circuitry for human laughter (Bilella et al, 2016), with diminution of laughter-type ultrasonics when those sites are damaged in rats (Roccaro-Waldmeyer et al, 2016). It is noteworthy that chronic subcortical DBS of the underlying SEEKING System in humans is robustly anti-depressive (Schlaepfer et al, 2013).…”

Eliminating the VGlut2-Dependent Glutamatergic Transmission of Parvalbumin-Expressing Neurons Leads to Deficits in Locomotion and Vocalization, Decreased Pain Sensitivity, and Increased Dominance

“…Since our study was originally driven by our interest in exploring the functions of the hypothalamic parvafox nucleus, these behavioral tests were mainly selected based on the connections of the parvafox nucleus with the periaqueductal gray matter (PAG). These connections preferentially indicate a possible involvement of the parvafox nucleus in analgesia, vocalization, and defense circuits (Celio et al, 2013 ; Bilella et al, 2016 ; Szabolcsi et al, 2017 ). In addition, a study that evaluated the effects of interfering with the fast synaptic inhibition onto PV-expressing neurons (Leppä et al, 2011 ) has also contributed to our selection of behavioral tests.…”

Reduction in 50-kHz call-numbers and suppression of tickling-associated positive affective behaviour after lesioning of the lateral hypothalamic parvafox nucleus in rats

“…The nucleus is located in the tuberal part of the ventrolateral hypothalamus, between the optic tract and the fornix [5][6][7]. Experiments in which anterograde tracers, particularly Cre-recombinase-dependent viral ones, have been injected into PV-Cre or Foxb1-Cre mice, have revealed the parvafox nucleus to project mainly to the periaqueductal grey matter (PAG), and, more specifically, to the ventrolateral [8] and the dorsolateral [9] columns. Furthermore, in-situ hybridization has disclosed PV-expressing neurons of the parvafox nucleus to be glutamatergic and thus excitatory [10], in contrast to those in most other brain areas, such as the neocortex, the hippocampus and the cerebellum [11].…”

“…The lateral hypothalamus has been ascribed a role in the functioning of the larynx [20] and pharynx [21], as well as in the control of vocalization [22]. Preliminary experiments in which Cre-dependent tracers were injected into the parvafox nucleus have disclosed a projection to the nucleus retroambiguus [9], which contains premotor interneurons capable to produce the motor actions required for vocalization [23]. In addition to its role in the control of vocalization, the lateral hypothalamus also harbours neuronal representations of reward value [24][25][26].…”