NEUROPHYSIOLOGY OF CONVERGING SYNAPTIC INPUTS FROM THE RAT PREFRONTALCORTEX, AMYGDALA, MIDLINE THALAMUS, AND HIPPOCAMPAL-FORMATION ONTO SINGLE NEURONS OF THE CAUDATE PUTAMEN AND NUCLEUS-ACCUMBENS/

Neurophysiological responses mediated by projections from five telence phalic and diencephalic regions (the infra- and prelimbic portions of the prefrontal cortex, amygdala, midline and intralaminar thalamic nuc lei, entorhinal cortex and subiculum/CA1) to the caudate/putamen (Cpu) and nucleus accumbens (Acb) of the dorsal and ventral striatum were s tudied in chloral-hydrate-anesthetized rats. Both extra- and intracell ular in vivo recording techniques were used. A retrograde tracer (whea tgerm agglutinin-apo-horseradish peroxidase-5 nm colloidal Gold) was d eposited in some animals in the vicinity of recording sites to confirm that stimulating electrodes were located near cells that projected to the striatum. Electrical stimulation of these five regions, respectiv ely, evoked excitatory responses in 60%, 22%, 51%, 25%, and 17% of str iatal neurons. Some responses, particularly with thalamic stimulation, showed short-term frequency potentiation in which 5/s stimulation inc reased the probability of spike firing. About half of responsive cells showed convergent excitation to more than one stimulating site. It wa s possible with convergent excitatory responses to show synaptic inter actions: simultaneous activation of more than one site produced spatia l and temporal summation to increase the probability of spike firing. Up to 5-way convergence onto single striatal neurons and up to 3-way i nteractions could be shown. These results indicate that functional inf luences from the hippocampal formation can converge with other excitat ory input onto single striatal neurons to effect synaptic integration. (C) 1996 Wiley-Liss, Inc.