Stimulation of the dorsomedial nucleus (DMH) or the perifornical area (PeF) of the hypothalamus activates breathing. The descending neuronal pathways that mediate this response are unknown. In the present experiments we test the possibility that this pathway includes a relay in the retrotrapezoid nucleus (RTN). The RTN resides at the rostral end of the medulla oblongata and consists of intrinsically pH-sensitive glutamatergic neurons that are proposed to contribute to CO2 stabilization by regulating the activity of the Central Respiratory Pattern Generator (CPG). The experiments were done in adult isofl urane-anesthetized rats. Stimulation of DMH/PeF with the selective GABAA receptor antagonist gabazine increased phrenic nerve activity and the discharge rate of simultaneously recorded RTN units. This upregulation was observed at all levels of end-expiratory CO2. After silencing the CPG with intravenous morphine (10–15 mg/kg), hypothalamic stimulation was still capable of enhancing RTN activity. In addition, both DMH/PeF stimulation or hypercapnia greatly increased the number of RTN neurons that expressed Fos when compared to rats maintained under control hypocapnic conditions. We conclude that the DMH/PeF region of the hypothalamus controls respiration at least in part by regulating the activity of the retrotrapezoid nucleus. Support: HL74011, HL 28785.
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.