Responses of the nucleus accumbens following fornix/fimbria stimulation in the rat: identification and long-term potentiation of mono-and polysynaptic pathways Boeijinga, P.H.; Mulder, A.B.; Pennartz, C.M.A.; Manshanden, I.; Lopes da Silva, F.H.
Published in: Neuroscience
Link to publicationCitation for published version (APA): Boeijinga, P. H., Mulder, A. B., Pennartz, C. M. A., Manshanden, I., & Lopes da Silva, F. H. (1993). Responses of the nucleus accumbens following fornix/fimbria stimulation in the rat: identification and long-term potentiation of mono-and polysynaptic pathways. Neuroscience, 53, 3-24.
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Download date: 12 May 2018Neuroscience Vol. 53, No. 4, pp. 1049-1058. 1993 Printed in Great Britain 0306-4522/93 $6.00 + 0. Abstract-The nucleus accumbens occupies a strategic position as an interface between limbic cortex and midbrain structures involved in motor performance. The fornix-fimbria carries limbic inputs to the ventral striatum, namely by way of fibers originating in the CAl/subiculum and projecting to the nucleus accumbens. It also carries fibers arising in the septal area that project to the hippocampal formation, and projection fibers to other areas of the rostra1 forebrain from Ammon's horn. Electrical stimulation of this bundle causes characteristic field potentials both in the nucleus accumbens and in the subiculum. In rats, under halothane anesthesia, the responses evoked by fornix/fimbria stimulation in the nucleus accumbens consist of two main positive peaks (at 10 and 25 ms, referred to as P10 and P25, respectively). PlO represents monosynaptic activation. We hypothesized that P25 reflects the activation of a polysynaptic loop, i.e. a fornix-fimbria hippocampal loop in series with the fibers that arise in the subiculum and project to the nucleus accumbens. To test this hypothesis, we reversibly blocked the fibers projecting caudally to the hippocampus by a local anesthetic (lidocaine) and the glutamatergic transmission through the CAl/subiculum by a local injection of kynurenic acid. Both manipulations yielded a reversible depression of about 90% of the P25 component while PlO remained unaffected as expected. In concert a strong reduction (to 243 1%) of control values of the responses evok...
