The stimulation or ablation of cerebellar structures has produced a variety of visceral responses, indicating a
cerebellar role in visceral functions. Studies using anterograde and retrograde tracing methods have revealed
connections between the hypothalamus and cerebellar structures. The aim of this study is to investigate the
cerebellar connections of the dorsomedial (DMH) and posterior hypothalamic nuclei using retrograde
axonal transport of horseradish peroxidase (HRP). In the present study, micro-injection of HRP restricted
within the borders of the DMH showed that the projections of this nucleus are not uniform throughout its
extent. The posterior DMH receives projections from the cerebellum, whereas the anterior DMH does not.
These projections were from the (greatest to least concentration) lateral (dentate), anterior interposed
(emboliform), and medial (fastigial) cerebellar nuclei. In addition, both the anterior and posterior DMH
receive projections from various areas of the brainstem which confirms earlier studies and provides detailed
descriptions. This study also demonstrates the distribution of labelled neurons to cerebellar and brainstem
nuclei following HRP injection into the posterior hypothalamic nucleus. It provides clear evidence for a
direct cerebellar nuclei-posterior DMH and cerebellar nuclei-posterior hypothalamic nucleus connections.
We suggest that the brainstem reticular nuclei and other connections, such as the solitary, trigeminal and
vestibular nuclei, of both DMH and posterior hypothalamus may contribute to the indirect
cerebellohypothalamic connections. These observations offer a new perspective on the question of how the
cerebellum may influence autonomic activity.