Effects of septal cholinergic lesion on rat exploratory behavior in an open-field

Abstract

The medial septum participates in the modulation of exploratory behavior triggered by novelty. Also, selective lesions of the cholinergic component of the septohippocampal system alter the habituation of rats to an elevated plus-maze without modifying anxiety indices. We investigated the effects of the intraseptal injection of the cholinergic immunotoxin 192 IgG-saporin (SAP) on the behavior of rats in an open-field. Thirty-nine male Wistar rats (weight: 194-230 g) were divided into three groups, non-injected controls and rats injected with either saline (0.5 µl) or SAP (237.5 ng/0.5 µl). Twelve days after surgery, the animals were placed in a square open-field (120 cm) and allowed to freely explore for 5 min. After the test, the rats were killed by decapitation and the septum, hippocampus and frontal cortex were removed and assayed for acetylcholinesterase activity. SAP increased acetylcholinesterase activity in the septum, hippocampus and frontal cortex and decreased the total distance run (9.15 ± 1.51 m) in comparison to controls (13.49 ± 0.91 m). The time spent in the center and at the periphery was not altered by SAP but the distance run was reduced during the first and second minutes (2.43 ± 0.36 and 1.75 ± 0.34 m) compared to controls (4.18 ± 0.26 and 3.14 ± 0.25 m). SAP-treated rats showed decreased but persistent exploration throughout the session. These results suggest that septohippocampal cholinergic mechanisms contribute to at least two critical processes, one related to the motivation to explore new environments and the other to the acquisition and storage of spatial information (i.e., spatial memory).

Original Nerve Growth Factor Mimetic Dipeptide GK-2 Restores Impaired Cognitive Functions in Rat Models of Alzheimer’s Disease

“…Transsection of the septo-hippocampal pathway led to impairment of EOR extinction over time, which was reflected at an almost constant level of the horizontal locomotor activity in the rats subjected to surgery over the entire period of testing (C e = 1). Similar results were also obtained by other researchers using this model [33, 34]. Impairment of the extinction of EOR under new conditions caused by the septo-hippocampal transsection was probably associated with abnormalities of the spatial memory [33].…”

“…Similar results were also obtained by other researchers using this model [33, 34]. Impairment of the extinction of EOR under new conditions caused by the septo-hippocampal transsection was probably associated with abnormalities of the spatial memory [33]. The animals subjected to surgery and treated with GK-2 demonstrated recovery of the ability to habituate (C e = 1.9) (Table 1).…”

“…The animal was carefully placed on the floor in the center of the arena; the number of squares and vertical stands crossed by it during 4 min was recorded using the RealTimer software program (Scientific and Production Company “Open science,” Russia). Transsection of the septo-hippocampal pathway in rats is known to cause impairment of the extinction of the exploratory orientation reaction (EOR) in the open field test [33, 34]. The EOR extinction coefficient, which represents the ability of rats to exhibit habituation, was calculated according to the equation C e = a/b , where a is the number of squares crossed in the group during the first minute of observation, and b is the number of squares crossed in the group during the last minute of observation.…”

Restoration of acetylcholinesterase activity byEuphorbia hirtain discrete brain regions of chronically stressed rats

“…The septohippocampal cholinergic pathways are thought to play a pivotal role in mediating the response to novel, stressful, and anxiogenic stimuli (Degroot et al, 2004;Lamprea et al, 2003). This pathway is involved in several cognitive functions such as learning, anxiety, motivation, exploratory, and ingestive behaviors (McNaughton & Gray, 2000).…”

Functional Development of Oligodendrocytes and Open-field Behavior in Developing Rats: An Approach Using Monoclonal Antibody to Immature Oligodendrocytes.

“…Thiamine, vitamin B 1 , deficiency also induced a decrease of AChE and altered some parameters of open-field performance [19]. Furthermore, cholinergic immunotoxin 192 IgG-saporin increased AChE activity in several brain regions and decreased motor activity in the open-field test [15]. Clomipramineinduced behavior depression was associated with an increase of AChE in the hippocampus and a decrease in the frontal cortex of adult rats [17].…”