Posterior hypothalamic modulation of light-evoked trigeminal neural activity and lacrimation

A. Katagiri, K. Okamoto, R. Thompson, D. A. Bereiter

Research output: Contribution to journalArticlepeer-review

11 Scopus citations

Abstract

Enhanced light sensitivity is a common feature of many neuro-ophthalmic conditions and some chronic headaches. Previously we reported that the bright light-evoked increases in trigeminal brainstem neural activity and lacrimation depended on a neurovascular link within the eye (Okamoto et al., 2012). However, the supraspinal pathways necessary for these light-evoked responses are not well defined. To assess the contribution of the posterior hypothalamic area (PH), a brain region closely associated with control of autonomic outflow, we injected bicuculline methiodide (BMI), a GABAa receptor antagonist, into the PH and determined its effect on the encoding properties of ocular neurons at the ventrolateral trigeminal interpolaris/caudalis transition (Vi/Vc) and caudalis/upper cervical cord junction (Vc/C1) regions and on reflex lacrimation in male rats under isoflurane anesthesia. BMI markedly reduced light-evoked (>80%) responses of Vi/Vc and Vc/C1 neurons at 10. min with partial recovery by 50. min after injection. BMI also reduced (>35%) the convergent cutaneous receptive field area of Vi/Vc and Vc/C1 ocular neurons indicating that both intra-ocular and periorbital cutaneous inputs were affected by changes in PH outflow. Light-evoked lacrimation was reduced by >35% at 10. min after BMI, while resting mean arterial pressure increased promptly and remained elevated (>20 mmHg) throughout the 50-min post-injection period. These results suggested that PH stimulation, acting in part through increased sympathetic activity, significantly inhibited light- and facial skin-evoked activity of ocular neurons at the Vi/Vc and Vc/C1 region. These data provide further support for the hypothesis that autonomic outflow plays a critical role in mediating light-evoked trigeminal brainstem neural activity and reflex lacrimation.

Original languageEnglish (US)
Pages (from-to)133-141
Number of pages9
JournalNeuroscience
Volume246
DOIs
StatePublished - Aug 9 2013

Bibliographical note

Funding Information:
The authors have no financial or other relationships to report that might lead to a conflict interest. This work was supported by a Grant from NIH ( EY021447 ).

Keywords

  • Descending control
  • Lacrimation
  • Light sensitivity
  • Posterior hypothalamus
  • Trigeminal subnucleus caudalis

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