Figure 4. Illustration of [³H]N-α-methylhistamine binding sites in representative sections of the cat brainstem.

Coronal sections from three representative animals: a control cat, a 1-week unilateral neurectomized cat (UVN 1 W), and a 1 week thioperamide-treated cat. Histamine H₃ receptor binding is decreased ipsilaterally in both caudal (A) and rostral (B) parts of the MVN 1 week after unilateral vestibular neurectomy, as compared to the control. Bilateral and symmetrical reductions are observed in the caudal and rostral MVN of the 1 week thioperamide-treated cat. A non-specific binding is represented at the bottom of the figure. IVN: inferior vestibular nucleus; MVN: medial vestibular nucleus; LVNd: lateral vestibular nucleus, dorsal part; LVNv: lateral vestibular nucleus, ventral part; PH: prepositus hypoglossi; CD: dorsal cochlear nucleus; CB: cerebellar cortex; 7G: genu of the facial nerve; 6: abducens nucleus. Scale bar: 1 mm. C, bar graph representing the quantitative evaluation of the effects of unilateral vestibular neurectomy or thioperamide treatment on the binding density of the agonist [³H]N-α-methylhistamine to H₃ receptors in the medial vestibular nuclei. The data are means and standard errors of the mean fmol of [³H]N-α-methylhistamine specifically bound per mg of protein from autoradiograms taken from 4 animals in each group. Data from the MVN are provided separately for each side (left/ipsilateral side (white bars) versus right/contralateral side (grey bars)). *Significantly different from the control data (cf. Table 1).