Inhibition of transmitter release by adenosine: are Ca²⁺ currents depressed or are the intracellular effects of Ca²⁺ impaired?

It has been suggested that blockade of nerve terminal Ca²⁺ channels by extracellular adenosine is responsible for the inhibitory effects of adenosine and its congeners on the secretion of neurotransmitter substances. Several lines of evidence, however, are not in accord with this suggestion. Eugene M. Silinsky presents evidence to indicate that the impairment of Ca²⁺-dependent processes at an intracellular site associated with the secretory apparatus provides the best single explanation for the inhibitory effects of adenosine derivatives on transmitter release.