Neuronal Convergence from Striatum and Dorsal Raphe to Antioromically Identified Nisro-striatal and Nigro- Thalamic Neurons

During ~-rhythm and B-activity a high degree of synchronization between the membrane voltage fluctuations of neurons in several parts of the hippocampal complex (HC) exists, resulting in high amplitude field potentials (FP) in these areas. Amplitude and phase relations of 0-EP, resp. ~-FP in different layers of these areas may provide information about the activation site at the somadendritic membranes of the resp. neuronal populatfons, and about the functional relations of these parts of HC during e-rhythm, resp. B-activity. FP were recorded simultaneously with a fixed and a moving semi-microelectrode (against reference) in the CAI field, fascia dentata and hilus of the dorsal HC of the urethane anesthetized rat during e-rhythm. Frequency analysis was applied to epochs of both signals at each position of the moving electrode. For the 8 (4~-5 e/s), resp. B (15-55c/s) component of the FP amplitude and phase profiles were made as a function of the anatomical location. 0-rhythm as well as B-activity had phase reversals, coupled with amplitude minima, in str.radiatum of CA] and in the molecular layer of the dentate area. O-rhythm had an amplitude maximum at the fissure and the 6 maximu~ was in the hilus. The membrane potentials simulated by a compartmental model (Rall) of a CAt pyramidal cell, a granular cell and a hilus cell have been used for calculation of their joint FP by a volume conductor model. Simulation of only few combinations of simultaneous local activation of the 3 cells led to FP-profiles similar to the profiles found experimentally for the e-, resp. the B-component of the FP. Th~s result leads~to 2 alternatives for the simultaneous synaptic activation of CAt pyramidal cells and dentate granular cells during 8-rhythm, resp. B-activity.