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Posterior hypothalamic modulation of ocular‐responsive trigeminal subnucleus caudalis neurons is mediated by O rexin‐ A and O rexin1 receptors
Author(s) -
Katagiri Ayano,
Okamoto Keiichiro,
Thompson Randall,
Rahman Mostafeezur,
Bereiter David A.
Publication year - 2014
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1111/ejn.12635
Subject(s) - disinhibition , brainstem , chemistry , orexin a , neuroscience , bicuculline , endocrinology , medicine , orexin , receptor , cnqx , antagonist , ampa receptor , psychology , neuropeptide , nmda receptor , biochemistry
Abstract Orexin‐A ( O x A ) is synthesized in posterior and lateral regions of the hypothalamus and contributes to homeostatic regulation of body functions including pain modulation. To determine if orexinergic mechanisms contribute to posterior hypothalamus ( PH )‐induced modulation of ocular input to subnucleus caudalis/upper cervical (Vc/C1) neurons, the orexin‐1 receptor antagonist SB 334867 was applied to the dorsal brainstem surface prior to PH disinhibition, by bicuculline methiodide, in male rats under isoflurane anesthesia. Ocular input to V c/ C 1 units by bright light or hypertonic saline was markedly reduced by PH disinhibition and reversed completely by local V c/ C 1 application of SB 334867. O x A applied to the V c/ C 1 surface mimicked the effects of PH disinhibition in a dose‐dependent manner. O x A ‐induced inhibition was prevented by co‐application of SB 334867, but not by the orexin‐2 receptor antagonist TCS Ox2 29. PH disinhibition and local O x A application also reduced the high threshold convergent cutaneous receptive field area of ocular units, suggesting widespread effects on somatic input to V c/ C 1 ocular units. V c/ C 1 application of O x A or SB 334867 alone did not affect the background discharge of ocular units and suggested that the PH – O x A influence on ocular unit activity was not tonically active. V c/ C 1 application of O x A or SB 334867 alone also did not alter mean arterial pressure, whereas PH disinhibition evoked prompt and sustained increases. These results suggest that stimulus‐evoked increases in PH outflow acts through O x A and orexin‐1 receptors to alter the encoding properties of trigeminal brainstem neurons responsive to input from the ocular surface and deep tissues of the eye.