Neuroanatomical evidences have revealed direct histaminergic projections from the tuberomamillary nucleus of the hypothalamus to almost whole brain including the cerebellum.Although,it has been proposed that the central histaminergic nervous system holds a key position in the regulation of many basic body functions,our previous studies have further demonstrated a postsynaptic excitatory effect of histamine on the cerebellar Purkinje and nuclear neurons via histamine H2 receptors,suggesting a modulatory effect of histamine on motor control.In the present study,using rat brain slice preparations and whole-cell patch recordings,the effects of histamine on two types of the cerebellar nuclear neurons were observed and the underlying ionic mechanisms were further investigated.Perfusing slices with 30,100,300 μM histamine produced an excitatory response in type Ⅰ neurons (projection neurons,n =17) instead of type Ⅱ neurons (intemeuron/local circuit neurons,n =11) within all three cerebellar nuclei (i.e.,fastigial,interpositus and dentate nucleus).