Deficits in operant behavior and alteration of CA1, CA3 hippocampal dendritic arborization due to subicular lesions

Abstract

The deficits in operant behavior and the alterations in dendritic arborizations of Cornu Ammonis 1 and Cornu Ammonis 3 (CA1 and CA3) hippocampal areas were investigated in subicular lesioned rats. The subjects were female Wistar rats aged 120 days, and were divided into four groups: one serving as age-matched untrained control, a second group received training and sham lesioning, a third group were only trained, and the fourth group were first trained and then subjected to subicular lesions. The rats were food-deprived 24 hours prior to operant behavior training sessions. Two training sessions for operant behavior with continuous reinforcement of 10 minutes duration per day were done during the shaping session, following which rats were allowed 10 minutes of operant food reward for 10 days. On the eleventh day, only the operant behavior and sham-operated rats were used for subicular lesion and sham surgery, respectively. After 72 hours of surgical recovery, operant behavioral testing was performed daily as before for a further period of 10 days. Later, all groups of rats were killed and the hippocampus was processed for rapid Golgi staining. Our results suggest that subicular lesions produce a significant reduction in operant learning. Further, the Golgi studies revealed a reduction in dendritic branching points and intersections of apical and basal CA1, CA3 neurons in lesioned rats.

What Is the Functional Significance of Chronic Stress-Induced CA3 Dendritic Retraction Within the Hippocampus?

“…Many studies have since shown that deprived conditions (Globus & Scheibel, 1967), deafferentation (Deitch & Rubel, 1984;Flores et al, 2005;Nutan & Meti, 1998;Works, Wilson, & Wellman, 2004), some clinical pathologies, and immune dysfunction (Grossman et al, 2003;Sakic et al, 1998) reduce dendritic arbors. In contrast, extensive training (Chang & Greenough, 1982;Nutan & Meti, 2000;Schallert, Kozlowski, Humm, & Cooke, 1997) or environmental enrichment (Camel, Withers, & Greenough, 1986;Faherty, Kerley, & Smeyne, 2003;Greenough & Volkmar, 1973;Kolb et al, 1998;Volkmar & Greenough, 1972) increase dendritic complexity. Additional studies have empirically confirmed that animals raised in enriched environments have measurable changes in the brain and show improved learning in a variety of mazes (see Rosenzweig & Bennett, 1996).…”