Distribution of ryanodine receptor-like immunoreactivity in mammalian central nervous system is consistent with its role in calcium-induced calcium release.

The distributions of ryanodine receptor-like immunoreactivity and Ca-ATPase-like immunoreactivity were identified in the guinea-pig and rat central nervous system using antibodies raised against the rabbit skeletal muscle ryanodine receptor and Ca-ATPase. In both guinea-pig and rat cerebellum, the ryanodine receptor-like immunoreactivity was restricted to the soma and dendrites of Purkinje cells. In the medulla, neuron somata in the hypoglossal nucleus were stained in both species, but in the dorsal motor nucleus of the vagus somata were stained in guinea-pigs but not in rats. This species difference in ryanodine receptor-like immunoreactivity is consistent with the species difference in expression of a ryanodine sensitive, calcium activated potassium conductance in neurons of the dorsal motor nucleus of the vagus. Immunoreactivity to Ca-ATPase was present in vagal motoneurons in both species with denser staining in the guinea-pig. The data further support the idea that, in neurons of the dorsal motor nucleus of the vagus, release of intracellular calcium stores via a ryanodine receptor activates a specific class of potassium channels, thereby modulating cell excitability.