Cerebellar inhibition and ICSS from stimulation in the area of the nucleus locus coeruleus.

The purpose of this study was to determine the relationship between intracranial self-stimulation (ICSS) and the long-lasting inhibition (LLI) of cerebellar Purkinje cells which are produced by stimulation around the dorsal pontine nucleus locus coeruleus (LC). No strong correlation was found between the dorsal pontine sites which produced LLI and those sites which yielded ICSS. Moreover, ICSS sites were no more effective than non-ICSS sites in producing LLI. LLI of Purkinje cells was produced most effectively by stimulation of an area dorsolateral to the LC where axons arising from the LC collect to ascend to the cerebellum. The LLI produced by stimulation of this dorsolateral region was less often associated with short latency excitations, compared to the LLI produced by stimulation of the cerebellar white matter. This characteristic may be useful as an indication of LC-produced LLI. Sites yielding ICSS were scattered around the LC but were most consistent ventrolateral to the LC. These results indicate that ICSS and LLI of Purkinje cells appear to be independent phenomena which depend on different mechanisms.