sfn2011

Sinha SP, Roland JJ, Servatius RJ, Pang KCH (2011) The role of medial septal/diagonal band GABAergic neurons in proactive interference: Effects of selective immunotoxic lesions in latent inhibition. Neuroscience 2011 Abstracts 199.22. Society for Neuroscience, Washington, DC.

Summary: The medial septum/diagonal band (MSDB) is a critical structure for learning and memory, yet the functional contributions of its individual neuronal populations (including cholinergic, GABAergic, glutamatergic and peptidergic cells) are still being characterized. Recent studies have implicated a contributing role for the GABAergic MSDB neuronal population, as selective immunotoxic GABAergic lesions of the MSDB (with GAT1-saporin) produce behavioral impairments in spatial and instrumental tasks. Compared to intact controls, rats with GABAergic MSDB lesions are impaired in learning new spatial locations in a delayed match to position procedure and also exhibit a slower rate of extinguishing a previously acquired avoidance response – behaviors that are consistent with an exacerbation of proactive interference. To further establish the role of these neurons in proactive interference, this study examined the effects of selective GABAergic MSDB lesions in latent inhibition (LI) of the classically conditioned eyeblink response. LI in delay eyeblink conditioning is a phenomenon in which pre-exposure to the conditioned stimulus (CS) interferes with the subjects’ ability to subsequently associate the CS with an unconditioned stimulus (US), resulting in slower acquisition of the conditioned response (CR). We hypothesized that if damage of GABAergic MSDB neurons increases proactive interference, then rats with selective lesions of these neurons would show facilitated LI. Male Sprague-Dawley rats (n=18) were administered either phosphate-buffered saline or GAT1-saporin via intracranial injection into the MSDB. After 7-10 days of recovery, electrodes were implanted into the upper eyelids of the rats for delivery of US and EMG recording. Conditioning began after another 5-7 days of recovery, with Day 1 consisting of 30 minutes of acclimation to the conditioning context. Day 2 began with either 30 presentations of the CS (82dB, 500ms white noise, 25 – 35s ITI) or context pre-exposure of equal duration, followed immediately by 100 paired CS-US trials (82 dB, 500ms white noise co-terminating with a 10V, 10ms square-wave stimulus). In preliminary results, intraseptal GAT1-saporin did not alter CR acquisition in context pre-exposed rats. Rats with GABAergic MSDB lesions continued to exhibit latent inhibition. These preliminary results do not support the idea that damage of GABAergic MSDB neurons increase proactive interference of the classically conditioned eyeblink response. Future studies will examine whether manipulations of the number of CS pre-exposures would facilitate LI in rats with GABAergic MSDB lesions.

Related Products: GAT1-SAP (Cat. #IT-32)

Cyr, M Maclaren DA, Bédard M-A, Clark SD, Mechawar N, Rochford J, Winn P (2011) Highly selective lesion of the cholinergic pedunculopontine neurons using a minimally-invasive angular stereotaxic surgery with the Diphteria-Urotensin-II neurotoxin in rat. Neuroscience 2011 Abstracts 37.06. Society for Neuroscience, Washington, DC.

Summary: Highly selective cholinergic lesions of the basal forebrain can be achieved with the immunotoxin 192-IgG saporin. This toxin has no effect however on the cholinergic neurons of the pedunculopontine tegmental nucleus (PPTg). For many years, most studies have used excitotoxins such as ibotenate, quisqualate, kainate, or N-methyl-D-aspartate, with a relative efficacy in targeting the PPTg cholinergic neurons, however these toxins also destroy the interdigitated glutamatergic and GABAergic neurons. More recently, selective cholinergic lesions were obtained with the Dtx-UII neurotoxin in both rats (Clark et al., 2007) and monkeys (Karachi et al., 2010). This toxin binds at the Urotensin-II receptor predominantly expressed in the pedunculopontine and the laterodorsal, but not the basal forebrain cholinergic nuclei. Because of the scattered distribution of the cholinergic neurons in the rat PPTg, infusion of the Dtx-UII requires multiple skull holes and needle lowering through areas containing critical blood vessels, increasing therefore surgery time, incidence of bleeding and mortality rate. Here, we report that these disadvantages can be avoided by doing a single Dtx-UII infusion, through an angular stereotaxic pathway. Results were contrasted with those obtained from the classical flat skull stereotaxic surgery used by Clark et al. (2007). Long Evans rats (males 250g – 300g) were operated according to three different methods. In group one, 3μl of Dtx-UII (3% concentration) was infused evenly in three unilateral stereotaxic coordinates along the PPTg (pars oralis, centralis, caudalis), using a flat skull position. In groups two and three, 2μl and 3μl of Dtx-UII were infused respectively using the angular stereotaxic method described by Wishaw et al. (1977). Incisor bar was elevated such that there was an 8º29’ angle (.147) between the latter and the interaural line. Following rat sacrifices, ChAT and NeuN immunohistochemistry were conducted in order to determine the cholinergic specificity and magnitude of the lesions. Results revealed similar PPTg cholinergic lesions between the three groups, reaching > 80% on the side of the lesions. Group 1 showed the greatest non specific lesions outside the PPTg, attributable to the needle pathways. This group of rats also showed the greatest number of surgical complications. We conclude that the cholinergic PPTg neurons can be optimally lesioned by using an angular surgical approach with the Dtx-UII toxin. Clark S.D., et al. (2007). J Neurochem., 102, 112-120. Karashi C., et al. (2010). J Clinical Investigation, 120, 2745-2754. Wishaw et al. (1977). Physiol. Behav., 19, 719-722.

Related Products: 192-IgG-SAP (Cat. #IT-01)

Parent M, Rosa-Neto P, Aliaga A, Soucy J-P, Bedard M-A (2011) [18F] fluoroethoxybenzovesamicol (FEOBV): A reliable PET radiocompound for the in-vivo assessment of cholinergic terminals. Neuroscience 2011 Abstracts 37.13. Society for Neuroscience, Washington, DC.

Summary: The vesicular acetylcholine transporter (VAChT) can be used as a surrogate target for PET imaging of brain cholinergic terminals. [18F]fluoroethoxybenzovesamicol (FEOBV) appears as a promising VAChT radioligand for PET imaging (Mulholand et al., 1998). Its pharmacokinetics, metabolism, and brain distribution have been well described in rodent and in primates (Kilbourn et al., 2010; Landry-St-Pierre et al., 2006; Soucy et al., 2010). The current study aims to assess the availability of VAChT binding sites in animals with presynaptic deficits induced by age or experimental lesions. We predict declines of FEOBV binding in brain regions innervated by cholinergic fibers. Twenty-one male Long-Evans rats were evenly divided in three groups: 1) Young rats (one month old); 2) Older rats (18 months old); 3) Rats with unilateral cholinergic lesions. In the latter group, 192-IgG-saporin (0.5 μg/μl) was infused under stereotaxic control into the nucleus basalis magnocellularis (NBM). A three weeks recovery period followed the surgery. FEOBV PET was conducted with a microPET (Siemens R4) on anesthetized animals. FEOBV (~11MBq) was injected and radioactivity measured in 27 sequential time frames of increasing duration, from 30 s to 5 min, for a total duration of 60 min. Images were reconstructed using a Maximum A Posteriori (MAP) algorithm, coregistered to a typical rat MRI template, and binding potential (BP) was calculated using the cerebellar cortex as reference tissue. Student t-tests were carried out at the voxel level: 1) Between lesioned (n=7) and non-lesioned (n=14) rats; 2) Between young (n=7) and old (n=7) non-lesioned rats. In lesioned rats, maximal BP reduction was observed in the ventral frontal cortex on the side of the lesion (t=6.5, p<0.0005, µ=41.88 mm3). Aged rats show significant clusters of BP reduction in both hippocampi (t=7.5 p<0.0005 24.61 mm3). We conclude that FEOBV PET allows quantification of cholinergic denervation following both normal aging and surgically induced cholinergic lesions.

Related Products: 192-IgG-SAP (Cat. #IT-01)

Pacheco-Herrero M, Thyssen D, Ramos-Rodriguez J, Berrocoso E, Bacskai B, Garcia-Alloza M (2011) Rapid beta-amyloid deposition and behavioural impairment after cholinergic denervation in APPswe/PS1dE9. Neuroscience 2011 Abstracts 47.02. Society for Neuroscience, Washington, DC.

Summary: Alzheimer’s disease (AD) is the most common cause of dementia. Although the ultimate neurotoxic mechanisms are not known, extensive evidence supports the role of amyloid-beta (Aβ) deposition as senile plaques (SP) in the disease. On the other hand, neuronal loss is the pathological feature that best correlates with the duration and severity of the illness and specifically, cholinergic denervation of the basal forebrain seems to be a good predictor of clinical dementia in AD. A close relationship has been documented between Aβ deposition and neurodegeneration, however, whether specific neurodegeneration may lead to senile plaque deposition remains unclear. We addressed this by inducing selective cholinergic lesions in APPswe/PS1dE9 mice with murine p-75 saporin, an inmunotoxin that selectively removes cholinergic innervation. We performed intracerebroventricular murine p-75 lesions in animals with an incipient (~3 months) and robust (~7 months of age) Aβ deposition and removed ~50% of basal forebrain cholinergic innervation to cortex and hippocampus. Immediately after injections, cranial windows were implanted and Aβ deposition was monitored in vivo and in real time in the cortex using methoxy-XO4 and multiphoton microscopy. We observed increased SP deposition as soon as 1 week after the lesion. We further corroborated our in vivo data post-mortem, using anti- Aβ and anti-fibrils antibodies as well as thioflavin S staining, both in the cortex and the hippocampus. 7 days after the surgery, when the lesion is established, animals were tested in the new object discrimination and Morris water maze tests. We observed an early memory impairment in young lesioned mice (~3 months) and this effect worsened with age (~7 months of age), when Aβ deposition is more robust. Altogether, our data suggest that cholinergic denervation may contribute to the deposition of Aβ and synergistically contribute to the cognitive impairment observed in AD.

Related Products: mu p75-SAP (Cat. #IT-16)

Holschbach MA, Lonstein JS (2011) Diminished norepinephrine release in the BSTv decreases anxiety but does not promote maternal behavior in nulliparous female rats. Neuroscience 2011 Abstracts 86.06. Society for Neuroscience, Washington, DC.

Summary: Postpartum caregiving heavily depends on both increased motivation to interact with offspring and decreased emotional reactivity. The early postpartum period is associated with reduced anxiety in mammals, which may promote contact with potentially anxiogenic young. The ventral bed nucleus of the stria terminalis (BSTv) is associated with both anxiety and maternal behaviors in laboratory rats and may be a site of integration for mediating tradeoffs between mothering and emotional reactivity. Our laboratory has previously shown that increasing norepinphrine (NE) release in the BSTv of postpartum rats via infusion of an autoreceptor antagonist increases dams’ anxiety behaviors to levels seen in untreated virgin rats. Interestingly, this treatment also disrupts maternal retrieval of pups (Smith and Lonstein, SFN 2009). Unlike postpartum rats, nulliparous females are not spontaneously maternal, and we hypothesized that if NE release in the BSTv disrupts maternal behaviors even in highly motivated postpartum rats, it may greatly hinder expression of maternal behaviors in virgins. To investigate whether depleting NE input to the BSTv is sufficient to reduce anxiety and promote maternal behavior in virgin female rats we injected an antiserum- based neurotoxin selective for noradrenergic fibers and cells (anti-dopamine beta-hydroxylase-saporin; anti-DBH-SAP; 50 mg/side), into the BSTv of ovariectomized virgin female rats. Two weeks later, we examined females’ anxiety behavior in an elevated plus maze and the next day began a maternal sensitization procedure. We placed three recently fed pups into each animal’s homecage and observed behavior for the following fifteen minutes each day until rats exhibited full maternal behavior (i.e. retrieved all three pups to a common nest site and hovered over them) during three consecutive tests. Histological analysis of the brains confirmed that anti-DBH-SAP greatly reduced NE fiber content in the BSTv. Compared to control animals injected with artificial CSF, animals injected with anti-DBH-SAP showed reduced anxiety in an elevated plus maze. Anti-DBH-SAP did not, however, reduce the latency to show full maternal behavior. Thus, although reduced anxiety permits or promotes expression of maternal behaviors in already motivated postpartum rats, reducing BSTv-mediated anxiety is not sufficient to facilitate maternal responsiveness without otherwise activating maternal motivational systems.

Related Products: Anti-DBH-SAP (Cat. #IT-03)

Ritter S, Li A-J, Wang Q, Dinh TT (2011) Basal metabolic substrate utilization is altered by lesion of hindbrain catecholamine neurons that innervate the medial hypothalamus and substrate selection during glucoprivation is impaired. Neuroscience 2011 Abstracts 88.05. Society for Neuroscience, Washington, DC.

Summary: Central injection of the targeted immunotoxin, anti-dopamine beta hydroxylase (DBH)-saporin (DSAP), retrogradely and selectively lesions norepinephrine (NE) and epinephrine (E) neurons with projections to the injection site. Previous work has shown that DSAP injections targeting the hypothalamic paraventricular nucleus eliminate key counterregulatory responses to acute glucose deficit, including feeding and corticosterone secretion. To examine the role of these NE an E neurons in metabolic control under basal conditions, we injected rats in the PVH with DSAP or control unconjugated saporin (SAP) and analyzed their metabolic profiles using metabolic chambers (Columbus Instruments). Rats were maintained on a standard pelleted rodent diet. We found that the respiratory exchange ratio (RER) was consistently elevated in DSAP rats across the entire circadian cycle under basal conditions, compared to the RER of SAP controls, indicating increased dependence on carbohydrate utilization. Metabolic rate and activity did not differ between groups. This result suggests a chronic enhancement of glucose mobilization or an impairment of the ability to mobilize fatty acids in the DSAP rats. We also found that when challenged by 2-deoxy-D-glucose induced glucoprivation, SAP controls exhibited a rapid decrease in RER, indicating a switch to fat metabolism, whereas DSAP rats did not exhibit this response. Together these results favor the possibility that a central mechanism for fat mobilization is impaired in DSAP rats and that this impairment is reflected under both basal and glucoprivic conditions. The previously reported observation that PVH DSAP-injected rats exhibit a slowly-developing obesity also supports this possibility. Additional findings suggest that this impairment may be due to the loss of NE/E control of corticosterone secretion in the DSAP rats.

Related Products: Anti-DBH-SAP (Cat. #IT-03), , Saporin (Cat. #PR-01)