Neural hyperactivity in the amygdala induced by chronic treatment of rats with analgesics may elucidate the mechanisms underlying psychiatric comorbidities associated with medication-overuse headache.

Background: Patients with medication-overuse headache suffer not only from chronic headache, but often from psychiatric comorbidities, such as anxiety and depression. The mechanisms underlying these comorbidities are unclear, but the amygdala is likely to be involved in their pathogenesis. To investigate the mechanisms underlying the comorbidities we used elevated plus maze and open field tests to assess anxiety-like behavior in rats chronically treated with analgesics.

Estrous Cycle Induces Peripheral Sensitization in Trigeminal Ganglion Neurons: An Animal Model of Menstrual Migraine.

Background: Many women experience menstrual migraines that develop into recurrent migraine attacks during menstruation. In the human menstrual cycle, the estrogen level fluctuates according to changes in the follicular and luteal phases. The rat estrous cycle is used as an animal model to study the effects of estrogen fluctuation.

The estrous cycle modulates voltage-gated ion channels in trigeminal ganglion neurons.

Migraines typically occur more frequently in women than men because of the effects of estrogen on both the frequency and severity of migraine attacks. Many women suffer from migraine attacks during menstruation, which are known as menstrual migraines. The pathophysiology of menstrual migraines can be explored by using the rat estrous cycle, which shows a cyclical fluctuation of estrogen level that resembles the menstrual cycle.