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Aim This study charts the growth of the scientific journal literature on headache for 30+ years (1983-2014). Methods Using the Web of Science, articles published in four two-year periods (1983-1984, 1993-1994, 2003-2004, 2013-2014) from journals indexed in the Science Citation Index Expanded database were retrieved and analyzed. Results From 1983-1984 to 2013-2014, the scientific literature on headache increased nearly fourfold (3.8) from 468 to 1776 articles; the number of participating countries more than doubled (26 to 67); and the two most prolific countries in each period were the USA and Italy. While several European countries (Italy, Germany, UK and Denmark) were among the top 10 in each period, the notable appearance of Turkey, China and Brazil among the top 10 in 2013-2014 indicates the growing geographic spread of publications on headache research. Meanwhile, the comet-like distribution of journals has not changed: two journals, Headache and Cephalalgia, persist throughout as the nucleus, with the tail increasing more than threefold from 141 journals in 1983-1984 to 462 in 2013-2014. Conclusion Our study follows the recent growth and spread of the scientific literature on headache research and should stimulate further bibliometric investigation in this field.

While functional imaging and deep brain stimulation studies point to a pivotal role of the hypothalamus in the pathophysiology of migraine and trigeminal autonomic cephalalgias, the circuitry and the mechanisms underlying the modulation of medullary trigeminovascular (Sp5C) neu-rons have not been fully identified. We investigated the existence of a direct anatomo-functional relationship between hypothalamic excitability disturbances and modifications of the activities of Sp5C neurons in the rat. Anterograde and retrograde neuronal anatomical tracing, intrahy-pothalamic microinjections, extracellular single-unit recordings of Sp5C neurons, and behavioral trials were used in this study. We found that neurons of the paraventricular nucleus of the hypothalamus (P VN) send descending projections to the superior salivatory nucleus, a region that gives rise to parasympathetic outflow to cephalic and ocular/nasal structures. PVN cells project also to laminae I and outer II of the Sp5C. Microinjections of the GABAa agonist muscimol into PVN inhibit both basal and meningeal-evoked activities of Sp5C neurons. Such inhibitions were reduced in acutely restrained stressed rats. GABAa antagonist gabazine infusions into the PVN facilitate meningeal-evoked responses of Sp5C neurons. PVN injections of the neuropeptide pituitary adenylate cyclase activating peptide (PACAP38) enhance Sp5C basal activities, whereas the antagonist PACAP6-38 depresses all types of Sp5C activities. 5-HT1B/D receptor agonist naratriptan infusion confined to the PVN depresses both basal and meningeal-evoked Sp5C activities. Our findings suggest that paraventricular hypothalamic neurons directly control both spontaneous and evoked activities of Sp5C neurons and could act either as modulators or triggers of migraine and/or trigeminal autonomic cephalalgias by integrating nociceptive, autonomic, and stress processing mechanisms. [ABSTRACT FROM AUTHOR]