Medial vestibular nucleus in the guinea-pig: histaminergic receptors - I. An in vitro study

Antihistaminergic drugs are currently used for the symptomatic treatment of vestibular related syndromes such as vertigo and motion sickness. We therefore investigated whether histamine could modulate the firing of medial vestibular nuclei neurones (MVNn). Recently, we have demonstrated that different cell types are present among MVNn in guinea-pig brainstem slices. Bath-application of histamine at 10^-4 or 10^-5 M induced a small membrane depolarization accompanied by a slight decrease in membrane resistance and a reversible increase in spontaneous firing in all MVN cell types. These effects were presumably postsynaptic as they persisted in a low calcium/high magnesium solution. Using a variety of agonists and antagonists of histamine receptors (H₁, H₂ and H₃), we conclude that these effects are mediated by H₂ receptors. The companion paper is concerned with an in vivo study of the histaminergic modulation of the vestibular function (Yabe et al., in press).