Inhaled 5-HT_{1B /1D} Receptor Antagonist Attenuates Sumatriptan-Induced Sensitization of Capsaicin-Sensitive Lung Vagal...

Sumatriptan, an antimigraine drug, is known to cause adverse chest symptoms such as dyspnea and chest tightness. We previously showed that sumatriptan sensitized capsaicin-sensitive lung vagal (CSLV) afferents in rats, a mechanism potentially underlying these symptoms. This sensitizing effect was abolished by intravenous GR127935, a 5-HT_1B/1D receptor antagonist. Therefore, to develop a potential therapeutic strategy, we hypothesized that targeting GR127935 to the lungs, rather than delivering it systemically, could prevent sumatriptan-induced chest discomfort by reducing CSLV-afferent sensitization without compromising sumatriptan's antimigraine efficacy within the trigeminovascular system.

Experiments were performed in anesthetized male Brown-Norway rats. CSLV-afferent excitability and afferent-mediated airway reflexes were assessed using single-fiber recordings and respiratory pattern monitoring. The antimigraine efficacy of sumatriptan was evaluated based on its inhibitory effect on dural plasma protein extravasation evoked by unilateral electrical stimulation of the trigeminal ganglion.

Intravenous sumatriptan potentiated capsaicin-evoked CSLV-afferent discharges and afferent-mediated airway responses. However, pretreatment with inhaled GR127935 significantly blocked this potentiating effect. The sumatriptan's antimigraine efficacy was not affected by inhaled GR127935, but was reduced by intravenous GR127935. Consistently, intravenous, but not inhaled GR127935, altered sumatriptan-induced hypotension, indicating that pulmonary delivery minimized systemic effects. Moreover, inhaled GR127935 did not change baseline cardiorespiratory parameters or fiber activity, suggesting it is unlikely to cause adverse cardiorespiratory effects.

Inhalation of a 5-HT_1B/1D receptor antagonist effectively prevented sumatriptan-induced sensitization of CSLV afferents without diminishing sumatriptan's antimigraine efficacy. Our findings suggest that inhaled 5-HT_1B/1D antagonists may offer a promising strategy to prevent or treat sumatriptan-induced adverse chest symptoms.