Br. J. Pharmacol. (1992), 106, 25-32

'."

Macmillan Press Ltd, 1992

Adenosine modulation of calcium currents in postganglionic neurones of avian cultured ciliary ganglia 'Max R. Bennett, R. Kerr & G. Khurana The Neurobiology Research Centre, University of Sydney, N.S.W. 2006, Australia 1 Calcium currents in postganglionic neurones of cultured 7- to 10-day embryonic avian ciliary ganglia analyzed under whole-cell voltage-clamp and their modulation by 2-chloroadenosine determined. 2 In the presence of tetrodotoxin (200 nM) in the medium to block the Na+ current and CsCl (105 mM) in the patch-clamp electrode to block the K+ current, two different components of the calcium currents (transient and sustained) were identified on the basis of their voltage-dependent kinetics as well as their sensitivity to the dihydropyridine agonist Bay K 8644 and antagonist nifedipine. 3 The sustained current inactivated very slowly (T >1000 iMs; for test potentials from -20 mV to + 40 mV) but was reactivated at a holding potential (Vh) of -40 mV. The current was increased on average over 50% by 1 gM of Bay K 8644 at a test potential of 0 mV and decreased over 35% by 1 JAM were

of

nifedipine.

4 The transient current inactivated slowly (t