The Septohippocampal Connection: Some Behavioral and Anatomical Relationships
Daniel P. Kimble John P. Vicedomini University of Oregon
Disruptions of septohippocampal circuitry have profound behavioral, electrophysiological, and anatomical effects. Various research efforts have been directed at ameliorating the deficits caused by such damage by introducing neural and/or nonneural tissues. These implantation procedures have included the introduction of fetal brain tissue ( Björklund & Stenevi, 1977; Gage, Björklund, Stenevi, & Dunnett, 1985), amnionic membrane ( Gage et al., 1988), genetically engineered fibroblasts ( Gage et al., 1987), chromaffin cells from the adrenal gland ( Freed et al., 1981) or direct administration of nerve growth factor (NGF; Hefti, 1986; Will & Hefti, 1985; Will, Hefti, Pallage, & Toniolo, 1988). Implanted tissue may also place neurotrophic factors (NTFs) such as NGF into the vicinity of the lesion.
In this chapter we discuss three experiments related to the potential role of NTFs in influencing septohippocampal connections and behavior following central nervous system (CNS) lesions in the adult rat. Hefti, Denton, Knüsel, and Lapchak ( 1993) offered a useful definition of neurotrophic factors as "endogenous soluble proteins regulating survival, growth, morphological plasticity, or synthesis of proteins for differentiated functions of neurons" (p. 25). In the first two experiments we examined the behavioral effects of various tissue grafts placed into cavities produced by either anterior hippocampal or fimbria-fornix lesions. A third experiment compared the neuroanatomical effects exerted on septal and diagonal band neurons by septohippocampal axotomy or by neurotoxic lesions of either dentate granule cells or CA3/4 pyramidal neurons.