EFFECTS OF A CAMP ANALOG SIMULATE THE DISTINCT COMPONENTS OF LONG-TERM POTENTIATION IN CA1 REGION OF RAT HIPPOCAMPUS

Bath application of the cAMP analogue, dibutyryl cyclic adenosine 3',5 '-monophosphate (dibutyryl cyclic AMP; dbcAMP) to rat hippocampal slic es was found to potentiate both the CA1 population spike and populatio n excitatory post-synaptic potential (EPSP) slope. dbcAMP (500-1000 mu M) was applied to slices for 30 min; following washout the population EPSP slope was potentiated for at least 30 min to a mean value of 51% above the drug-free baseline value. The population spike was similarl y potentiated to a mean value of 64% above baseline after dbcAMP washo ut. dbcAMP-induced population EPSP slope potentiation occluded long-te rm potentiation (LTP) induced by high frequency electrical stimulation , and LTP occluded dbcAMP-induced EPSP slope potentiation. Earlier inv estigations (Pockett et al., Neuroscience, 52 (1993) 229-236) using 20 0 mu M dbcAMP reported similar potentiation of population spike but no potentiation of EPSP slope. These experiments support the hypothesis that the two components of LTP (Bliss and Lynch, In P.W. Landfield and S.A. Deadwyler (Eds.), Long-term Potentiation: from Biophysics to Beh aviour, Alan R. Liss, New York, 1988, pp. 3-72) in the CA1 area of rat hippocampus both involve distinct cAMP-dependent mechanisms.