ELECTROPHYSIOLOGICAL RESPONSE OF NEURONS OF THE MEDIODORSAL NUCLEUS OF THE THALAMUS TO THE STIMULATION OF THE NUCLEUS-ACCUMBENS IN THE RAT

The neural connections from the nucleus accumbens to the mediodorsal n ucleus of the thalamus were investigated in urethane-anesthetized rats . Extracellular recordings were made from 84 spontaneously firing neur ons in the mediodorsal nucleus of the thalamus while the nucleus accum bens was electrically stimulated. The most frequent response to nucleu s accumbens stimulation was inhibition of the firing rate of the neuro ns with orthodromic response (mean latency: 13.5 +/- 1.9 ms). A low pe rcentage (16.6%) of neurons showed excitatory response followed by an inhibitory period (mean latency: 3.5 +/- 1.2 ms). These electrophysiol ogical results demonstrate the existence of connections between the nu cleus accumbens and the mediodorsal nucleus of the thalamus. These pro jections have an inhibitory role in the spontaneous activity of mediod orsal, neurons and they may play a modulatory role in motivational beh aviors and cognitive functions.