sfn2007

Gompf HS, Fuller PM, Saper CB, Lu J (2007) Locus coeruleus (LC) is involved in sustaining arousal. Neuroscience 2007 Abstracts 736.3/UU16. Society for Neuroscience, San Diego, CA.

Summary: The locus coeruleus (LC) has traditionally been thought to be involved in arousal; however, lesions of the LC have minimal effects on basal sleep-wake behavior. We propose that the LC instead may be required to sustain arousal under conditions of environmental challenge. To test this hypothesis, we intraventricularly injected saline, or 0.25, 0.5, or 1µg anti-DBH-saporin (DBH-SAP selectively lesions the LC), and implanted EEG/EMG electrodes. On recording days, each animal was paired with a normal rat (social interaction) and presented with novel objects every hour for 5 hours from ZT 6 to ZT 11. We then repeated the same experiment for 2.5 hrs and immunostained tissue for Fos and TH or Fos and DBH. We also repeated the same experiment in rats with unilateral LC lesion by 6-OHDA. During 5 hr of stimulation with novel objects and social interaction (distracting stimuli, DS), controls or partial LC lesioned animals (0.25 µg DBH-SAP) spent 83 ± 8% and 92 ± 4% awake respectively (n = 3 and 4, p = 0.4) whereas animals with complete LC lesions (0.5 and 1 µg) spent significantly less time in wakefulness (59 ± 4% and 66 ± 5% respectively, n = 3 and 4, p = 0.0005). The reduction of wakefulness occurred primarily during the second 30 mins of each hour. Following DS exposure, Fos was highly expressed in the cerebral cortex in both LC lesioned groups and controls. Furthermore, we found a correlation (R2 = 0.79) between the remaining LC neurons and wakefulness under DS. Rats with loss of one LC showed no changes in wakefulness, and Fos was highly and symmetrically induced in the cerebral cortex. Our results suggest that the LC is specifically involved in sustaining arousal.

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Martin MM, Carter LA, Jones JL, Winter SS, Wallace DG (2007) Organization of food protection behavior is differentially influenced by hippocampal and cortical cholinergic deafferentation. Neuroscience 2007 Abstracts 742.6/AAA9. Society for Neuroscience, San Diego, CA.

Summary: Previous work has suggested that rats use temporal information to organize their food protection behaviors. Studies have demonstrated different roles for hippocampal and cortical cholinergic function in processing of temporal information in standard interval timing procedures. The present study examined the role of hippocampal and cortical cholinergic function on the organization of food protection behavior. Long Evans female rats received either injections of 192 IgG-Saporin (SAP) or saline (SHAM) into the medial septum (MS) or nucleus basalis (NB). Subsequent to recovery, rats were placed into an enclosure and provided a hazelnut in the presence of an unoperated conspecific. All rats engaged in dodging or bracing behaviors to prevent the theft of the hazelnut. During a dodge, the rat places the food item in its mouth to use both fore- and hind-limbs to escape the approaching conspecific. In contrast, during a brace, the rat’s forelimbs maintain contact with the food item, and only the hind limbs are used to make shorter lateral movements. Only rats receiving sham lesions displayed a consistent transition from primarily engaging in dodging behavior to primarily engaging in bracing behavior during the consumption of the hazelnut. The MS SAP group displayed a disruption in their temporal organization of food protection behaviors. Although the NB SAP animals displayed impaired responding to the approaching conspecific (resulting in frequent thefts), their food protection behaviors tended to exhibit temporal organization. These results provide further evidence as to the role of the basal forebrain cholinergic system in temporal organization of behavior.

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

Wallace DG, Knapp SK, Silver JA, Martin MM, Winter SS (2007) Selective hippocampal cholinergic deafferentation disrupts exploratory trip organization. Neuroscience 2007 Abstracts 743.17/BBB11. Society for Neuroscience, San Diego, CA.

Summary: Rats organize their exploration of an environment around a central location or home base. Movements away from the home base are characterized as a series of slow progressions punctuated by stops. Subsequent to the last stop, the homeward segment is a single, rapid progression associated with a consistent temporal pacing of linear speeds. Observing these characteristics of exploratory behavior independent of environmental cue availability or familiarity has supported rats’ use of self-movement cues generated after departing the home base to estimate the distance and direction back to the home base. The current study investigated the effects of selective hippocampal cholinergic deafferentation on home base establishment and exploratory trip organization. Long Evans female rats either received injections of 192 IgG-Saporin (SAP) or saline (SHAM) into the medial septum. Subsequent to recovery, rats were placed on a large circular table with access to a refuge under complete dark conditions (infrared cameras and goggles were used to visualize the rat). Although all rats established a home base in the refuge, impairments in exploratory trip organization specific to the homeward segment were observed in SAP rats. Specifically, SAP rats displayed inconsistent temporal pacing of homeward segment linear speeds. These observations are consistent with a role for hippocampal cholinergic function in processing self-movement cues.

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

Browning PG, Gaffan D, Baxter MG (2007) Severe visual learning impairments in monkeys with combined but not separate lesions of the temporal cortical cholinergic system and the fornix. Neuroscience 2007 Abstracts 341.7. Society for Neuroscience, San Diego, CA.

Summary: A dense amnesia can be produced in the monkey by sectioning the anterior temporal stem, amygdala and fornix, a procedure which deafferents temporal cortex from modulatory inputs from the midbrain and basal forebrain. The present experiment investigated the neurochemical specificity of these severe learning impairments by selectively destroying cholinergic projections to the entire inferior temporal cortex by making multiple injections of the immunotoxin ME20.4-saporin into the inferior temporal cortex bilaterally. Six male macaque monkeys were preoperatively trained to learn new object-in-place discrimination problems each day until they could rapidly learn many such problems within a testing session. The monkeys then underwent surgery and received either injections of immunotoxin (n=3) or injections of saline (n=3). Both groups of monkeys were unimpaired when postoperative and preoperative performance were compared. Each monkey then underwent a second surgery to transect the fornix. After this surgery monkeys who had previously received injections of immunotoxin into temporal cortex showed a severe learning impairment, whereas monkeys who had previously received injections of saline showed a mild impairment. Monkeys with the combined immunotoxin plus fornix lesion were also severely impaired at concurrent object discrimination learning. These results suggest that different neuromodulatory inputs to inferior temporal cortex may act in concert to support cortical plasticity in visual learning such that the loss of acetylcholine only is not sufficient to disrupt normal learning behavior. The results also suggest that in monkeys, as in humans with Alzheimer’s disease, severe memory impairments occur only when a loss of acetylcholine projections to cortex is accompanied by organic tissue damage.

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Baxter MG, Kyriazis DA, Croxson PL (2007) Cholinergic depletion of prefrontal cortex does not impair episodic memory or strategy implementation in rhesus monkeys. Neuroscience 2007 Abstracts 341.9. Society for Neuroscience, San Diego, CA.

Summary: The prefrontal cortex is involved in regulating multiple aspects of memory, decision-making, and cognitive control. Cholinergic input to prefrontal cortex is thought to be involved in supporting its functions. To examine this hypothesis we tested 4 rhesus monkeys (3 male) with cholinergic depletion of ventrolateral prefrontal cortex (N=2) or the entire prefrontal cortex, excluding its medial aspect (N=2). Selective cholinergic depletion was produced by multiple injections of the immunotoxin ME20.4-saporin (0.02 ug/ul) into the prefrontal cortex. These monkeys were tested on two tasks that each require frontal-inferotemporal interaction, as well as an intact ventrolateral prefrontal cortex. The first, strategy implementation, requires monkeys to apply different choice strategies to different categories of objects in order to maximize the rate of reward delivery, and engages decision-making and cognitive control. The second, scene memory, is a test of episodic memory in which monkeys rapidly learn 20 new object-in-place scene discrimination problems within a single test session. Cholinergic depletions of prefrontal cortex, whether they were limited to ventrolateral prefrontal cortex or included the whole of lateral and orbital prefrontal cortex, were without effect on either strategy implementation or new scene learning relative to each monkey’s preoperative performance. Thus, episodic memory and strategy implementation can proceed normally even with severely disrupted cholinergic input, so loss of cholinergic input on its own cannot explain impaired prefrontal function in conditions such as Alzheimer’s disease. Acetylcholine may work in tandem with other neuromodulators to affect prefrontal cortex function; alternatively, it may only be involved in very specific aspects of cortical function, for example representational plasticity.

Related Products: ME20.4-SAP (Cat. #IT-15)

Tai S, Ma J, Leung L (2007) Vestibular activation stimulates cholinergic system in the hippocampus. Neuroscience 2007 Abstracts 399.21/OO13. Society for Neuroscience, San Diego, CA.

Summary: The vestibular system has been suggested to participate in spatial navigation, a function ascribed to the hippocampus. We examined the mechanisms that induced hippocampal theta, a 4-10 Hz rhythm in the electroencephalogram (EEG), during vestibular activation in rats. Freely behaving rats were rotated at various speeds, on a vertical axis, in the light or dark. Hippocampal EEGs were recorded by implanted electrodes in hippocampal CA1, and analyzed by spectral analysis. A clear hippocampal theta rhythm was induced during immobility by rotations at different speeds (20-70 rpm). The rotation-induced theta was abolished, in light and dark settings, by muscarinic cholinergic receptor antagonist atropine sulfate (50 mg/kg i.p.) but not by atropine methyl nitrate (50 mg/kg i.p.), which did not pass the blood-brain barrier. Rotation-induced theta was attenuated in rats in which the cholinergic neurons in the medial septum (MS) were lesioned by 192 IgG-saporin (0.14 µg/0.4 µl infused bilaterally into the MS 10-20 days prior to the experiments). Cholinergic lesion in the MS was confirmed by a depletion of MS neurons that stained positively for choline acetyltransferase and an absence of acetylcholinesterase histochemical staining in the hippocampus. Bilateral lesion of the vestibular receptors (by 0.1 ml intratympanic injection of 300 mg/ml sodium arsanilate) also attenuated the rotation-induced theta rhythm. Vestibular lesion was confirmed by the contact righting test where lesioned rats will “walk” upside down on a Plexiglas sheet placed in contact with the soles of the feet while intact rats will right themselves immediately. In summary, an atropine-sensitive hippocampal theta is activated by septohippocampal cholinergic neurons which are in turn activated by vestibular stimulation. Vestibular-activated septohippocampal cholinergic activity is likely an important component of spatial navigation.

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

Burk JA, Altemose KE, Lowder MW (2007) Effects of spatial cueing on visual discrimination performance of rats following loss of basal forebrain corticopetal cholinergic neurons. Neuroscience 2007 Abstracts 424.4/HHH3. Society for Neuroscience, San Diego, CA.

Summary: Basal forebrain corticopetal cholinergic neurons are necessary for normal attentional performance. However, the exact attentional task parameters that are sufficient for inducing deficits following loss of basal forebrain corticopetal cholinergic neurons remain unclear. In Experiment 1, rats were trained to perform a spatially cued visual discrimination task (press a lever under an illuminated panel light) with explicit attentional demands removed. Animals then received infusions of the cholinergic immunotoxin, 192IgG-saporin, or saline into the basal forebrain. All animals were then tested in the same task trained before surgery and then task parameters, including the duration of visual signals and the inter-trial interval, were manipulated in order to tax attentional processing. Lesioned animals exhibited an initial increase in response latencies immediately following surgery but this deficit was not observed when task demands were increased. When the task was modified to remove spatial cueing, by presenting visual signals or no signal from a centrally-located panel light, lesioned animals exhibited an increase in lever press latencies compared to sham-lesioned animals. In Experiment 2, rats were trained in a visual discrimination task that, within each session, had blocks of trials with or without spatial cueing, using procedures similar to Experiment 1. After receiving intra-basalis infusions of 192IgG-saporin or saline, animals were tested for 12 sessions in the same task trained before surgery followed by one session in which the inter-trial interval was decreased. Lesioned animals did not exhibit deficits immediately following surgery, but did show elevated lever press latencies compared to sham-lesioned animals when the inter-trial interval was decreased. There was a trend for this lesioned-induced deficit to be more pronounced when spatial cues were not present. These experiments indicate that cortical acetylcholine is critical for maintaining normal visual discrimination performance when spatial cueing is not available. We speculate that, under conditions in which spatial cueing is unavailable, the lesion-induced increased lever press latencies reflect a disruption in recalling rules for an appropriate response.

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

Butt AE, Amodeo D, Flesher M, Marsa K, Holt R, Lladones R, Olney R, Haynes J, Kinney-Hurd BL, Dach N (2007) 192 IgG-saporin lesions of the cholinergic basal forebrain disrupt selective attention and trace conditioning but spare delay and long-delay conditioning. Neuroscience 2007 Abstracts 424.9/HHH8. Society for Neuroscience, San Diego, CA.

Summary: Recent research suggests that Pavlovian trace conditioning, but not delay conditioning, is a form of declarative memory that requires attention, where both of these processes depend on specific brain systems. For example, past research has shown that although amnesiac humans with damage to the hippocampus (HPC) acquire a normal conditioned response (CR) in delay conditioning paradigms, where the conditioned stimulus (CS) and unconditioned stimulus (US) partly overlap, they fail to acquire the CR in trace conditioning paradigms, where the CS and US are separated in time. Others have shown that the anterior cingulate cortex (ACC) in rats and the medial prefrontal cortex (mPFC) in rabbits are similarly necessary for trace but not delay conditioning. The basal forebrain cholinergic system (BFCS) has projections to the mPFC, ACC, and HPC. Given that each of these regions is critical for trace but not delay conditioning, we hypothesized that lesions of the BFCS using 192 IgG-saporin (SAP) would selectively impair trace but not delay or long-delay appetitive conditioning in rats. Additionally, given evidence suggesting BFCS involvement in attention, it was hypothesized that the addition of varying levels of distraction during the trace conditioning task would cause progressively greater degrees of impairment in the BFCS lesion groups compared to controls. In contrast, neither the control groups nor the BFCS lesion groups were expected be negatively affected by the addition of a distracting stimulus in the delay and long-delay conditioning tasks. Rats received bilateral SAP lesions or sham lesions of the BFCS prior to conditioning with a white noise CS and sucrose pellet US in either a delay, long-delay, or 10 s trace conditioning paradigm. Separate groups of BFCS lesion and control rats were subjected to varying levels of visual distraction (flashing house light) in each paradigm; no distraction, low distraction (continuously blinking light), and high distraction (intermittent, unpredictable flashing light). Results supported our hypotheses, with the BFCS lesion groups showing normal delay and long-delay conditioning regardless of level of distraction. In contrast, trace conditioning was impaired in the BFCS lesion groups, with progressively greater degrees of impairment occurring with greater levels of distraction, and complete disruption of learning in the high distraction condition. Together, these experiments suggest that the BFCS is necessary for normal trace conditioning, and that the BFCS is critically involved in selective attention tasks where animals must discriminate relevant stimuli from distracting background stimuli.

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

Likhtik E, Popa D, Apergis-Schoute J, Fidacaro GA, Pare D (2007) Lesion of intercalated (ITC) amygdala neurons interfere with extinction of classically conditioned fear responses. Neuroscience 2007 Abstracts 426.6/HHH29. Society for Neuroscience, San Diego, CA.

Summary: The acquisition of conditioned fear responses (CRs) is thought to involve the potentiation of synapses conveying information about the conditioned stimulus (CS) to the basolateral (BLA) amygdala. Expression of CRs would depend on the transfer of potentiated CS inputs by the BLA to the central amygdala (CE). In contrast, the mechanisms of extinction remain controversial. It has been proposed that ITC neurons, which receive BLA inputs and generate feedforward inhibition in CE, are in a key position to mediate extinction. In this view, NMDA-dependent potentiation of BLA inputs to ITC cells during extinction training, would dampen the impact of CS-related BLA activity on CE neurons, inhibiting CRs. However, this idea is difficult to test because ITC cells occur in small, lateromedially dispersed clusters, making conventional lesioning methods inadequate. Here, we took advantage of the fact that, compared to the rest of the amygdala, ITC cells express a much higher concentration of mu opioid receptors (muORs). As a result, we could lesion them by performing local injections of a peptide-toxin conjugate (demorphin conjugated to saporin, D-Sap) that selectively targets cells expressing muORs. Control rats received injections of saporin conjugated to a blank peptide (B-Sap). On Day 1, intact rats were subjected to a standard cued fear conditioning protocol in context A. On Day 2, they received 20 CS alone presentations in a different context (B). On Day 3, rats then received either D-Sap or B-Sap injections in the ITC cell masses. One week later, extinction recall was tested in context B with 10 CS alone presentations. Compared to control (B-Sap) rats (n=10), ITC-lesioned rats (n=5) had an extinction deficit (ANOVA, F=11.687, p = 0.005). Post-hoc t-tests comparing % time freezing during the first five or last five CSs revealed that rats with ITC lesions had significantly higher freezing levels throughout the extinction recall test (p<0.002 for both tests). These differences were not attributable to a non-specific increase in freezing or anxiety levels as exploratory behaviors in a novel open field in control and ITC-lesioned rats were indistinguishable. Overall, these results indicate that ITC cells are involved in the expression of extinction.

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Arias-Carrion O, Hernandez-Martinez H, Drucker-Colin R (2007) Hypocretin/orexin neuronal loss increases adult neurogenesis. Neuroscience 2007 Abstracts 456.14/C7. Society for Neuroscience, San Diego, CA.

Summary: Adult neurogenesis in the subventricular zone (SVZ) is subjected to physiological regulation and can be modified by brain injuries. The sleep disorder narcolepsy may now be considered a neurodegenerative disease, as there is a massive reduction in the number of neurons containing the neuropeptide, hypocretin (HCRT). In the present study, we investigate the relationship between hypocretin neuronal loss and adult neurogenesis. The neurotoxin, hypocretin-2-saporin (HCRT2-SAP), was administered bilaterally to the lateral hypothalamus (LH) to lesion HCRT neurons. Five weeks after HCRT2-SAP administration a loss of HCRT-ir neurons into LH was produced. In normal animals, a high density of HCRT-ir fibers was found in the septum and was poor in the corpus callosum and striatum. These densities decreased in lesioned animals. To label dividing cells, we used 5-bromo-2′-deoxyuridine (BrdU). BrdU was injected twice daily during days 10-14 after lesion, saline or control procedure. Animals were killed at 3 weeks after the last BrdU injection. Experimental depletion of HCRT in rats increases precursor cell proliferation in the SVZ and subependimal layer of 3rd ventricle. However, we don’t find BrdU/HCRT double-labeled cells in the subependimal zone or LH. These observations suggest that the HCRT is a negative factor in adult neurogenesis.

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