Interactions between septal and entorhinal inputs to the rat dentate gyrus: facilitation effects.
We examined facilitation effects between the medial septum and perforant path inputs to the dentate gyrus for the four possible combinations of paired-pulse activation. Facilitation effects occurred in all cases. The largest facilitation effects occurred when the septal pulse served as the conditioning pulse for the population spike subsequently evoked by a perforant path pulse. Using 3 pulses, we also examined the influence of septal activation on paired-pulse facilitation of the perforant path-granule cell population spike. A septal stimulation pulse, applied 6-10 ms prior to the onset of the population spike evoked by a perforant path conditioning pulse, did not affect the perforant path-dentate test response at any interpulse interval. If the septal pulse occurred immediately prior to population spike onset, however, there was a significantly greater depression of the test response from 70-3000 ms, but no effect at early intervals (20-50 ms). The effect of the septal pulse appears more consistent with a direct action of the septal terminals on granule cells than with an indirect action via the recurrent inhibitory interneurons.
D000818:Animals; D004558:Electric Stimulation; D005071:Evoked Potentials; D006624:Hippocampus / Q000502:physiology*; D008297:Male; D009433:Neural Inhibition; D051381:Rats; D011919:Rats, Inbred Strains; D011930:Reaction Time / Q000502:physiology; D012686:Septal Nuclei / Q000502:physiology*; D013569:Synapses / Q000502:physiology; D009435:Synaptic Transmission