Stimulation of the hypothalamic paraventricular nucleus modulates cardiorespiratory responses via oxytocinergic innervation of neurons in pre-Bötzinger complex

Abstract

Previously we reported that oxytocin (OT)-containing neurons of the hypothalamic paraventricular nucleus (PVN) project to the preBötzinger complex (preBötC) region and phrenic motoneurons innervating the diaphragm (D). The aim of these studies was to determine pathways involved in PVN stimulation-induced changes in upper airway and chest wall pumping muscle activity. In addition, we determined the role of OT-containing neurons in the PVN in mediating increased respiratory output elicited by PVN stimulation. Neuroanatomical experiments, using pseudorabies virus (PRV) as a transneuronal tracer in C8 spinalectomized animals showed that PVN neurons project to hypoglossal motoneurons innervating the genioglossus (GG) muscle. Furthermore, microinjection of the PVN with bicuculline, a GABA A receptor antagonist, significantly increased (P<0.05) peak electromyographic activity of GG (GG EMG ) and of D EMG , frequency discharge, and arterial blood pressure (BP) and heart rate. Prior injection of oxytocin antagonist [d-(CH2)5, Tyr(Me)2,Orn8]-vasotocin(OVT) intracisternally or blockade of oxytocin receptors in the preBötC region with oxytocin antagonist L-368,899, diminished GG EMG and D EMG responses and blunted the increase in BP and heart rate to PVN stimulation. These data show that PVN stimulation affects central regulatory mechanisms via the preBötC region controlling both respiratory and cardiovascular functions. The parallel changes induced by PVN stimulation were mediated mainly through an OT-OT receptor signaling pathway.

Pituitary adenylate cyclase-activating polypeptide maintains neonatal breathing but not metabolism during mild reductions in ambient temperature

“…It is equally possible that PACAP maintains V E by stimulating neurons that are activated by reductions in ambient and/or body temperature but do not participate directly in the chemoreflexes. We note that neurons within the preoptic and paraventricular nuclei of the hypothalamus that are involved in temperature regulation also project to and stimulate phrenic motoneurons (6,19,24,25) and receive dense innervation from PACAP-positive axons (2,9,34). Finally, it is also possible that the effect of PACAP on the ventilatory responses to cooling are indirect, being mediated by other neuropeptides or hormones.…”

Regulation of Breathing and Autonomic Outflows by Chemoreceptors

“…A possible connection between PVH and respiration could involve the catecholaminergic neurons of the VLM which are excited by oxytocin or vasopressin and are in turn capable of stimulating breathing (2, 397). Based on anterograde tracing data the direct projections from the PVH to the hypoglossal nucleus, deduced from PRV studies (259) do not appear to exist (136). The projections from PVH to the ventral horn of the spinal cord, postulated on the basis of retrograde transport evidence (463) are also not observed by anterograde tracing.…”

Melanocortin-4 receptor mRNA expressed in sympathetic outflow neurons to brown adipose tissue: neuroanatomical and functional evidence

“…Plasmids containing the 289-bp cDNA sequence corresponding to nucleotides 707-995 of the published sequence of rat MC4-R (GenBank accession no. U 67863.1) were linearized with HindIII and XhoI restriction enzymes (Promega, Madison, WI) and transcribed in vitro using T7 and SP6 RNA polymerases (Stratagene, La Jolla, CA) in the presence of 35 S-labeled UTP (PerkinElmer, Boston, MA) to generate sense and antisense probes, respectively. The specifics of this sequence including the cloning procedure followed are detailed in our previous report (53), where we describe colocalization of MC4-R mRNA with PRV-infected SNS outflow neurons when PRV is injected into inguinal WAT.…”

“…Brain sections were rinsed in 2ϫ SSC (1ϫ ϭ 0.15 M sodium chloride and 0.015 M sodium citrate), dehydrated in ascending concentrations of ethanol, delipidated with chloroform, rehydrated in descending concentrations of ethanol, deaminated in acetic anhydride (0.25%)-triethanolamine (0.1 M in saline), and then incubated in formamide (50%; with 2ϫ SSC, 0.1% sodium dodecyl sulfate, 25 mM dithiothreitol). The sections were then hybridized with 35 S-labeled MC4-R cRNA or sense control probes (30,000 cpm/l) at 57°C overnight. The following day, the sections were cooled to room temperature, rinsed in 1ϫ SSC, 2ϫ SSCformamide (1:1, 30 min at 53°C), incubated in RNase A (100 mg/ml), washed in 2ϫ SSC-formamide (1:1, 90 min at 57°C), and rinsed in 1ϫ SSC and in PBS (0.1 M; pH 7.4) for immunohistochemical processing to detect PRV in the same sections.…”

“…We also found that the hypoglossal nucleus (CN XII) had MC4-R ϩ PRV-labeled and PRV-only infected cells. CN XII is known for control of the intrinsic muscles of the tongue and muscles associated with shoulder movement; however, CN XII also is involved in cardiovascular and especially respiratory circuits (35) involving the PVH, an area of high colocalization of PRV ϩ MC4-R mRNA cells, as well as modulation by the ROb (41), another area of high colocalization. It is not difficult to envision coordination of respiration, cardiovascular and BAT temperature responses to changes in ambient temperature.…”