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. Author manuscript; available in PMC: 2011 Oct 31.
Published in final edited form as: Respir Physiol Neurobiol. 2010 Feb 17;173(3):223–229. doi: 10.1016/j.resp.2010.02.006

Figure 4. Pivotal role of orexin in connecting state-dependent behavioral regulation system and cardiorespiratory homeostatic reflex pathways.

Figure 4

Among known connections from/to orexinergic neurons in the hypothalamus, selected brain nuclei are depicted that are relevant to this review (thick lines). Many nuclei located at both of input (MR, RTN, LC, NTS) and output (cardiorespiratory motor neurons) interfaces in the homeostatic cardiorespiratory reflex pathway receive projections from orexinergic neurons (right half). Simultaneously, orexinergic connections are engaged in sleep/wake regulation and emotional stress-induced behavioral changes (left half). Thus, orexin can modulate cardiorespiratory homeostasis in a state-dependent manner. Arrows indicate a probable excitatory connection and circles indicate an inhibitory connection. Connections shown in thin lines are either direct or indirect. Abbreviations: AMG, amygdala; BNST, bed nucleus of the stria terminalis; DR, dorsal raphe; LC, locus coeruleus; MLR, medullary locomotor region; MR, medullary raphe; NTS, nucleus tractus solitarius; PAG, periaqueductal gray; PVN, paraventricular nucleus; RTN, retrotrapezoid nucleus; RVLM, rostral ventrolateral medulla where sympathetic premotor neurons are located; SCN, suprachiasmatic nucleus; TMN, tuberomammillary nucleus; VLPO, ventrolateral preoptic nucleus.