Somatically recorded Ca-currents in guinea-pig hippocampal and olfactory cortex neurones are resistant to adenosine action.

Inward membrane currents were recorded in tetrodotoxin-treated neurones of hippocampus and olfactory cortex in vitro after impalement with CsCl-containing microelectrodes to suppress potassium conductances. They were blocked by the Ca2+ -channel blocker Cd2+ but were unaffected by adenosine alone (up to 1 mM), adenosine (20 microM) in the presence of the uptake blocker dipyridamole (1 microM) or the stable analogue cyclohexyladenosine (100 microM). This ineffectiveness of adenosine on Ca-currents was in contrast to its known potent suppression of synaptic transmission in these preparations, and its inhibition of Ca-dependent action potentials.