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Do GAT1-saporin lesions of the medial septum damage GABAergic afferents to the medial septum?
Gielow M, Roland J, Servatius, RJ Pang KCH (2010) Do GAT1-saporin lesions of the medial septum damage GABAergic afferents to the medial septum?. Neuroscience 2010 Abstracts 811.3/LLL66. Society for Neuroscience, San Diego, CA.
Summary: 192-IgG saporin is an antibody directed to the p75 receptor conjugated to the ribosomal-inactivating compound saporin. 192-IgG saporin has been widely used to selectively ablate cholinergic cells of the basal forebrain. Cholinergic lesions are typically made by injections of 192-IgG saporin at the soma in basal forebrain nuclei. However, 192-IgG saporin is also effective in damaging specific cholinergic projections by administration of the toxin in the axon terminal region. Recently, GAT1-saporin has been developed as a tool to selectively damage cells expressing the GABA transporter GAT1. GAT1-saporin combines an antibody to the GABA transporter GAT1 with saporin. GAT1 transporters are primarily localized to neurons and GAT1-saporin has been shown to selectively damage GABAergic neurons in the BNST and medial septum. Given the similarity to 192-IgG saporin, a major question is whether GAT1-saporin is effective in damaging GABAergic afferents to the area of administration. Our previous studies found that GAT1-saporin administered to the medial septum / diagonal band of Broca (MSDB) damages GABAergic septohippocampal neurons and impaired performance on delayed match to position tasks. While it seems likely that damage of GABAergic MSDB neurons is responsible for these behavioral impairments, one cannot rule out the possibility that destruction of GABAergic afferents to the MSDB may also contribute. Therefore, the present study was undertaken to determine whether GAT1-saporin lesions of the MSDB damage the GABAergic hippocamposeptal projection. Male Sprague Dawley rats received both fluorogold and either GAT1-saporin or vehicle in medial septum. Immunocytochemistry for choline acetyltransferase and parvalbumin confirmed the extent of the lesion. The majority of hippocamposeptal GABAergic neurons contain the neuropeptide somatostatin. Quantification of double-labeled hippocampal fluorogold-positive cell bodies with anti-somatostatin immunofluorescence was performed using unbiased stereology. Preliminary data suggest that GABAergic hippocamposeptal neurons are intact. These results will be important in understanding the damage produced by GAT1-saporin.
Related Products: GAT1-SAP (Cat. #IT-32)
Damage of GABAergic neurons in the medial septum-diagonal band (MSDB) reduces behaviorally-activated hippocampal acetylcholine efflux and impairs spatial working memory
Roland JJ, Janke KL, Savage LM, Servatius RJ, Pang KCH (2010) Damage of GABAergic neurons in the medial septum-diagonal band (MSDB) reduces behaviorally-activated hippocampal acetylcholine efflux and impairs spatial working memory. Neuroscience 2010 Abstracts 611.13/MMM64. Society for Neuroscience, San Diego, CA.
Summary: The septohippocampal pathway is mostly composed of cholinergic and GABAergic projections and has an established role in learning, memory and disorders of cognition. Most studies have focused on the role of the cholinergic system in learning, memory and disorders of cognition. Although MSDB cholinergic lesions do not result in learning impairments, changes in hippocampal acetylcholine (ACh) levels have been tied to memory functions where deficits or enhancements in memory were correlated with hippocampal ACh decreases or increases, respectively. The activity of MSDB cholinergic neurons is greatly influenced by GABAergic afferents, including those from GABAergic neurons within the MSDB. Recently, we’ve demonstrated that toxins that preferentially damage MSDB GABAergic neurons impair delayed match to position tasks, but not spatial reference memory. Interpretation of these results needs to take into account the fact that a MSDB GABAergic lesion would influence both septohippocampal cholinergic and GABAergic transmission. The current study examined the effect of MSDB GABAergic lesions on spontaneous alternation (Experiment 1) and a non-matching to position task (NMTP; Experiment 2) while concurrently using in vivo microdialysis to measure hippocampal ACh efflux. Adult male Sprague-Dawley rats received vehicle (PBS) or GABAergic (GAT-1 saporin) MSDB lesion and a hippocampal microdialysis cannula. In Experiment 1, treatment groups did not differ in terms of activity, alternation rates, or baseline and maze-activated ACh efflux. In Experiment 2, hippocampal ACh efflux was measured at two time points (early and late) across the acquisition of a delayed NMTP task. Overall, GAT1-saporin treated rats had lower accuracy scores across 10 days of maze training compared to the vehicle treated rats. Basal ACh release in the hippocampus was similar in vehicle and GAT1-saporin rats. During the two microdialysis sampling points, both groups of rats displayed significant increases in ACh efflux while performing the task. However, behaviorally activated ACh efflux was reduced in GABA-lesioned animals compared to vehicle treated rats. The results demonstrate that MSDB GABAergic lesions do not alter basal hippocampal ACh efflux, but can reduce ACh efflux when challenged cognitively. Future studies will attempt to determine whether reduced ACh efflux is due to damage of MSDB GABAergic neurons or a result of impaired working memory performance.
Related Products: GAT1-SAP (Cat. #IT-32)
Damage of GABAergic neurons in the medial septum impairs spatial working memory and extinction of active avoidance: Effects on proactive interference.
Pang KCH, Jiao X, Sinha S, Beck KD, Servatius RJ (2011) Damage of GABAergic neurons in the medial septum impairs spatial working memory and extinction of active avoidance: Effects on proactive interference. Hippocampus 21(8):835-846. doi: 10.1002/hipo.20799
Summary: Recent work implicates the medial septum (MS) and diagonal band (DB) in the control of proactive interference — forgetting older information when learning new information. Rats received GAT1-SAP (Cat. #IT-32) injections into the MS and the DB (162.5 ng and 130 ng respectively, the DB injections were bilateral). The results parallel other studies using different toxins, reinforcing the indications that GABAergic MSDB neurons are an integral part of proactive interference control.
Related Products: 192-IgG-SAP (Cat. #IT-01), GAT1-SAP (Cat. #IT-32)
Selective cholinergic and GABAergic lesions of the medial septum slows acquisition of the classically conditioned eyeblink response in rats.
Roland JJ, Janke KL, Gluck MA, Beck KD, Pang KCH, Servatius RJ (2009) Selective cholinergic and GABAergic lesions of the medial septum slows acquisition of the classically conditioned eyeblink response in rats. Neuroscience 2009 Abstracts 283.6/EE135. Society for Neuroscience, Chicago, IL.
Summary: Both human and animal studies have demonstrated that the hippocampus is not essential for the acquisition of delay eyeblink conditioning. However, nonselective medial septal damage, in both rabbits and humans, impaired acquisition of delayed eyeblink conditioning, as well as latent inhibition of eyeblink conditioning. The medial septum provides a major cholinergic and GABAergic afferent projection to the hippocampus, and the effects of medial septal damage is widely believed to occur through its connections to the hippocampus. Cholinergic muscarinic antagonists impaired delay eyeblink conditioning when administered systemically or directly into the hippocampus. Computational models also predicted the lack of effects on delay conditioning or latent inhibition of eyeblink conditioning caused by interference of the cholinergic septohippocampal system Recent studies have suggested that the GABAergic septohippocampal system may be a major site of action for scopolamine. Therefore, the current study examined the effect of selective cholinergic or GABAergic medial septal lesions on the classically conditioned eyeblink response. Adult male Sprague-Dawley rats received either a sham, cholinergic (192-IgG saporin) or GABAergic (GAT1-saporin) lesion in the MS/DB. Two weeks later, all animals were implanted with stimulating and recording electrodes in the periorbital muscle. Following recovery, all animals received three consecutive days of delay eyeblink conditioning. Each daily session consisted of 100 paired CS-US (conditional stimulus – unconditioned stimulus) trials with an average intertrial interval (ITI) of 30 seconds. The CS was a 500ms tone which co-terminated with the US, a 10ms, 10V periorbital stimulation. Our preliminary results shows that both cholinergic and GABAergic lesions impaired acquisition of delayed eyeblink conditioning, as compared to the sham-lesioned group. However, after three days of training all three treatment groups reached the same asymptotic performance. Future studies will assess the effects of combined cholinergic and GABAergic lesions and the effects of these septal lesions on latent inhibition of the conditioned eyeblink response.
Related Products: 192-IgG-SAP (Cat. #IT-01), GAT1-SAP (Cat. #IT-32)
Role of the medial septum on navigational strategy and shifting between strategies: Effects of selective cholinergic and GABAergic lesions.
Janke KL, Fazelinik S, Roland JJ, Servatius RJ, Servatius RJ, Servatius RJ, Pang K (2009) Role of the medial septum on navigational strategy and shifting between strategies: Effects of selective cholinergic and GABAergic lesions. Neuroscience 2009 Abstracts 283.5/EE134. Society for Neuroscience, Chicago, IL.
Summary: Cholinergic and GABAergic neurons are major components of the septohippocampal pathway, and comparisons between the two neuronal populations are important for understanding the function of medial septum-vertical limb of the diagonal band (MSDB). Recently, we have been investigating the importance of MSDB neurons in cognitive flexibility. Cognitive flexibility is commonly examined in reversal of stimulus-reward associations and attention set shifting. The present studies examine whether selective lesions of cholinergic or GABAergic MSDB neurons impair shifting between egocentric and allocentric navigation strategies. Sprague Dawley rats were administered saline, GAT1-saporin or 192-IgG saporin into the MSDB to produce no damage, selective GABAergic damage or selective cholinergic damage, respectively. Lesion verification will be performed using immunocytochemistry at the end of the studies. In a plus maze, rats started in one of two arms opposite each other (i.e., north and south arms) randomized across trials. On any single trial, the arm opposite the starting arm was blocked forming a T-maze. Rats have a choice of entering one of the remaining 2 arms (east or west arms) for food reinforcement. During the acquisition phase of the first study, rats were reinforced to enter a particular arm (east or west: allocentric response) regardless of their starting location. After they reached criteria (10 consecutive correct choices), the goal location was either reversed (east to west) or shifted to an egocentric response strategy (left or right turn). Animals that received either GAT-1-saporin (.26 ug/ul) or 192-IgG saporin (.217ug/ul) lesion reached criteria faster than saline treated rats. No significant effects of either lesion were observed on spatial reversal or strategy shifts. However, qualitative assessment of the damage suggests that GAT1-saporin may have produced an incomplete lesion. Therefore, a second study using GAT1-saporin at .325 ug/ul was conducted. For this study, half of the rats were trained on an egocentric strategy and the other rats are reinforced for an allocentric response. When rats reached criteria, half of each group was trained in a reversal learning or strategy shift. Preliminary data show that rats treated with GAT1-saporin or saline learned the initial egocentric or allocentric strategy at a similar rate. However, animals were faster to reach criteria in the allocentric condition than the egocentric condition. Reversal learning and strategy shifting in the second study is currently being assessed. The results of this study will provide important insight into the role of the MSDB in learning and cognitive flexibility.
Related Products: 192-IgG-SAP (Cat. #IT-01), GAT1-SAP (Cat. #IT-32)
A discrete GABAergic relay mediates medial prefrontal cortical inhibition of the neuroendocrine stress response.
Radley JJ, Gosselink KL, Sawchenko PE (2009) A discrete GABAergic relay mediates medial prefrontal cortical inhibition of the neuroendocrine stress response. J Neurosci 29:7330-7340. doi: 10.1523/JNEUROSCI.5924-08.2009
Summary: GABAergic neurons have been implicated in the negative regulation of the hypothalamic-pituitary-adrenal axis (HPA). In order to clarify GABAergic input to the paraventricular hypothalamic nucleus the authors injected 0.23 µg of GAT1-SAP (Cat. #IT-32) into the anterior bed nucleus of the stria terminalis. Both unilateral and bilateral injections were used. Rabbit IgG-SAP (Cat. #IT-35) was used as a control. The data indicate that the GABAergic neuronal population functions as proximate mediator of HPA-inhibitory limbic influences.
Related Products: GAT1-SAP (Cat. #IT-32), Rabbit IgG-SAP (Cat. #IT-35)
Role of medial septum-diagonal band of Broca neurons in cognitive flexibility
Pang K, Janke K, Servatius RJ (2008) Role of medial septum-diagonal band of Broca neurons in cognitive flexibility. Neuroscience 2008 Abstracts 89.20/SS37. Society for Neuroscience, Washington, DC.
Summary: Cholinergic and GABAergic neurons are major components of the septohippocampal pathway, and comparisons between the two neuronal populations are important for understanding the function of medial septum and vertical limb of the diagonal band (MSDB). Recently, we have been investigating the importance of MSDB neurons in cognitive flexibility. Cognitive flexibility is commonly examined in procedures that require reversal of stimulus-reward associations and those that require shifts in attention set, involving switching attention to different stimulus dimensions. Our recent studies demonstrated that selective damage of GABAergic but not cholinergic MSDB neurons impaired spatial reversal. The present study will determine whether selective lesions of cholinergic or GABAergic MSDB neurons impairs shifting of attentional set. Sprague Dawley rats will be administered saline, GAT1-saporin or 192-IgG saporin into the MSDB to produce no damage, selective GABAergic damage or selective cholinergic damage, respectively. Verification of the lesions will be performed using immunocytochemistry at the end of the study. The behavioral procedure will occur in a plus maze. Rats will start in one of two arms opposite each other (i.e., north and south arms) randomized across trials. On any single trial, the arm opposite the starting arm will be blocked forming a T-maze. Rats will have a choice of entering one of the remaining 2 arms (east or west arms) for food reinforcement. Half of the rats will be reinforced to make an egocentric response (left or right turn) and the other rats will be reinforced to go to a particular arm (east or west; allocentric response) regardless of starting location. After reaching criterion (10 consecutive correct choices), the goal location will be reversed (i.e., left turn to right turn or east to west arm) or shifted to a different dimension (i.e., left turn to east arm or west arm to right turn). It is expected that rats treated with GAT1-saporin, but not 192-saporin, will be impaired on the reversal procedure, similar to previous studies. Impairments in shifting attention set would suggest a global impairment in cognitive flexibility. However, an impairment in the reversal procedure but not shifting of attention set would be similar to recently described deficits in the nucleus basalis magnocellularis using ibotenic acid and 192-IgG saporin lesions (Tait and Brown, Behav Brain Res. 187:100, 2008). The results of this study will provide important insight into the role of the MSDB in learning, attention and cognitive flexibility.
Related Products: 192-IgG-SAP (Cat. #IT-01), GAT1-SAP (Cat. #IT-32)
Featured Article: Role of medial septal GABAergic neurons in learning and extinction: Effects of the novel GABA immunotoxin GAT1-SAP
Pang KCH, Jiao X, Servatius RJ (2008) Featured Article: Role of medial septal GABAergic neurons in learning and extinction: Effects of the novel GABA immunotoxin GAT1-SAP. Targeting Trends 9(1)
Related Products: GAT1-SAP (Cat. #IT-32)
Understanding the role of non-cholinergic medial septal neurons in learning and memory: Implications for disease- and aging-related impairments
Pang K, Sinha SP, Jiao X, Servatius RJ (2007) Understanding the role of non-cholinergic medial septal neurons in learning and memory: Implications for disease- and aging-related impairments. Neuroscience 2007 Abstracts 932.22/WW17. Society for Neuroscience, San Diego, CA.
Summary: The medial septum-diagonal band of Broca (MS) has an important function in learning and memory. Furthermore, degeneration of the MS may contribute to cognitive impairments associated with Alzheimer’s disease and normal aging. Because the MS contains several types of neurons, the neuronal population(s) involved in learning and memory has been actively investigated. Animal studies have mainly focused on the cholinergic neurons that project to the hippocampus. Although complete lesions of the MS or fimbria-fornix transaction leads to spatial memory impairments, selective damage of cholinergic MS neurons produces no or a mild impairment in spatial memory, suggesting an important role of non-cholinergic neurons. Most of these non-cholinergic neurons are GABAergic. Previously, we used low concentrations of kainic acid to examine the importance of non-cholinergic MS neurons in spatial memory. However, a more selective toxin for GABAergic neurons would facilitate research, as it has done for the cholinergic system. In the present study, we use a new GABAergic immunotoxin that combines an antibody to the GABA transporter GAT1 with saporin. GAT1-saporin was administered into the medial septum of male Sprague Dawley rats. Our preliminary results show that GABAergic septohippocampal neurons as assessed by parvalbumin-immunoreactivity were virtually eliminated, while cholinergic neurons were spared in the medial septum. Current work is focused on further characterizing the cell populations affected by GAT1-saporin. Preliminary behavioral results demonstrate that GABA MS lesions did not impair spatial reference memory in the initial acquisition of a water maze task. However, a deficit was observed in reversal learning. Further testing in a procedure where the escape platform moves to a new location every day showed that rats treated with GAT1-saporin were mildly impaired in within-session learning of the new platform location. These preliminary results demonstrate that intraseptal GAT1-saporin is effective in eliminating at least some populations of GABAergic neurons in the MS. Furthermore, the preliminary behavioral results are consistent with our previous results demonstrating that damage of non-cholinergic MS neurons produces a very specific impairment on reversal learning. In summary, GAT1-saporin may be a useful tool to examine the function of GABA MS neurons in learning and memory and their contribution to cognitive impairments in disease and aging.
Related Products: GAT1-SAP (Cat. #IT-32)
Effects of NBM lesions on selective attention in an interval timing task
McAuley J, Pang K (2007) Effects of NBM lesions on selective attention in an interval timing task. Neuroscience 2007 Abstracts 742.9. Society for Neuroscience, San Diego, CA.
Summary: Divided and sustained attention are impaired by damage to the nucleus basalis magnocellularis (NBM), which provides cholinergic and GABAergic input to the neocortex. The present study was performed to further investigate the role of the NBM in attention using a selective attention version of the peak-interval timing procedure. Male Fisher 344 rats were initially trained using a peak interval procedure to time a light stimulus, delivering reward for the first lever press after 12 s. Selective attention was then tested in distracter sessions where random tone bursts and house light flashes were presented on some trials, but not others. These distracter sessions were interleaved with non-distracter sessions that were identical to initial peak-interval training. Preliminary results in normal young rats show that peak times on un-reinforced probe trials with distraction were lengthened as compared to probe trials without distraction in the same session. Moreover, peak times on non-distracter probe trials were similar between distracter and non-distracter sessions. In these preliminary studies, the observed overestimation of time during selective attention testing was transient, supporting the view that attention modulates the rate of an internal clock. Current studies aim to determine the influence of selective cholinergic or GABAergic NBM lesions in this selective attention task.
Related Products: GAT1-SAP (Cat. #IT-32)