sfn2006

Vaucher EJ, Dotigny F (2006) Cell type specificity of the c-Fos immunoreactive neurons of cortical layer IV after patterned visual stimulation. Neuroscience 2006 Abstracts 545.28. Society for Neuroscience, Atlanta, GA.

Summary: The cortical processing of specific visual stimuli may be enhanced or suppressed by neuromodulators, such as acetylcholine or norepinephrine as early as in the primary visual area. We have recently shown using c-Fos immunoreactivity that the specific lesion of basal forebrain cholinergic projections abolished the visually-induced neuronal activity of the layer IV of the primary visual cortex. The present study investigated further which cell types immunoreactive for c-Fos were modulated by the cholinergic afferents. Twenty male Long Evans Rats (275-300g) were anaesthetized with urethane (1.3g/kg). C-Fos immunocytochemistry was used as a single cell resolution marker of functional activity induced by sinusoidal grating in the visual cortex in control condition, specific lesion of the cholinergic fibers using 192-IgG saporin, muscarinic inhibition by scopolamine (1mg/kg) or NMDA receptors inhibition by CPP (10mg/kg). c-Fos/Parvalbumin and c-Fos/rat-brain-pyramidal-cells-marker double immunocytochemistry was performed to determine the localization of the visually-induced c-Fos immunoreactivity within the GABAergic interneurons or pyramidal cells of the layer IV of the rat cortex. The results demonstrated that the c-Fos immunoreactivity evoked by patterned stimulation in layer IV was rarely (less than 5%) co-localized with either parvalbumin or rat-brain-pyramidal-cells-marker. In addition, this functional activity was blocked by a cholinergic deficit but was independent of NMDA receptors transmission, since their inhibition by CPP did not affect the activity-dependent c-Fos immunoreactivity. These results suggest an effect of the patterned visual stimulation and the cholinergic fibers on the excitatory spiny stellate cells rather than the GABAergic or pyramidal cells. It suggests a role of the basal forebrain cholinergic neurons in the modulation of the thalamo-cortical transmission rather than local cortical microcircuitry in the rat visual cortex.

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

Miller JP, McAuley JD, Pang KC (2006) Effects of selective cholinergic NBM lesions on short-interval timing. Neuroscience 2006 Abstracts 572.24. Society for Neuroscience, Atlanta, GA.

Summary: The nucleus basalis magnocellularis (NBM) and its connection to the frontal cortex are important for timing short durations and divided attention. Although the NBM provides the major cholinergic input to the frontal cortex, GABAergic and other neurons are also located in the NBM and project to neocortex. To examine the role of the NBM in timing and attention, previous investigators used non-selective lesions of the NBM using ibotenic acid (IBO). In the present study, we examined the importance of cholinergic NBM neurons in timing using the selective immunotoxin 192-IgG saporin (SAP). Fisher 344 rats were trained on a peak-interval (PI) procedure using fixed-intervals of 12 s and 24 s. Once trained, stereotaxic surgeries where conducted on the rats and either SAP or nothing (SHAM) was administered into the NBM to create selective cholinergic or control lesions respectively. Preliminary results show that SAP did not alter peak times (SHAM: 11.82 s & 22.59 s versus SAP: 11.98 s & 22.88 s) or coefficient of variability (CV, SHAM: 0.41 & 0.45 versus SAP: 0.44 & 0.47). However, upon inspection of the brains, SAP lesions did not reduce the number of cholinergic neurons in the NBM. In a separate study using the PI procedure with a single fixed-interval of 18 s, IBO altered timing accuracy as measured by the absolute difference in peak times (pre-op versus post-op: SHAM = 0.60 s; IBO = 1.94 s) and altered variability as measured by the change in CV (pre-op versus post-op: SHAM = 0.02; IBO = 0.20). Preliminary results with IBO showing a non-directional reduction in accuracy are different from previous studies that have reported systematic overestimation of duration, although in our study the damage caused by IBO was restricted to the anterior NBM. Current studies are further evaluating the role of NBM neurons in timing with more selective and complete cholinergic lesions using SAP and more complete non-selective lesions using IBO.

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

Wong YM, Webber MJ, Dickenson AH, Hunt SP (2006) Molecular changes in the dorsal horn that maintain inflammatory hyperalgesia are similar to those generated during long-term potentiation. Neuroscience 2006 Abstracts 642.17. Society for Neuroscience, Atlanta, GA.

Summary: The generation of LTP in deep dorsal horn neurons by noxious stimulation may be one mechanism whereby acute pain transforms into a chronic pain state. Spinal LTP requires the activation of a subset of superficial dorsal horn neurons that express the neurokinin-1 receptor (NK1-R) and are crucial for the initiation and maintenance of chronic pain states. These neurons participate in local spinal sensory processing and are the origin of a spino-bulbo-spinal loop that drives descending spinal facilitation. Spinal LTP is correlated with increased neuronal expression of the transcription factor zif268 in the superficial dorsal horn. Here, we examined if inflammatory pain states required LTP-like changes in gene expression that are dependent upon an intact lamina I pathway. We also asked if changing levels of zif268 regulated the glucocorticoid receptor (GR) gene, a downstream target of zif268. NK1 expressing neurons in lamina I of the lumbar spinal cord were selectively ablated using SP-SAP applied intrathecally. 28d later, rats were injected with Complete Freunds’ Adjuvant (CFA) (50%, 100μl) 2h prior to perfusion with 4% paraformaldehyde. Using immunohistochemistry, we found that while levels of c-fos immunoreactivity were unchanged by lamina I ablation, the levels of zif268 had decreased by 36% (p<0.05) compared to controls. We therefore treated rats intrathecally with zif268 antisense or missense oligonucleotides (0.16μg/μl/h) via implanted osmotic mini pumps and assessed the behavioural effects of zif268 ‘knockdown’ on inflammatory hyperalgesia. Animals were perfused 4 days after CFA inflammation and protein levels of zif268 and GR were assessed by immunohistochemistry. Antisense, but not missense zif268 treatment, reduced the levels of zif268 by 37% and reduced behavioural allodynia by 40%, but only at days 2-4 post CFA. Levels of GR were also reduced by 30% following zif268 antisense treatment. We therefore applied antisense and missense GR probes intrathecally.This reduced the inflammatory hyperalgesia score by 38% but again only on days 2-4. These results suggest the zif268 gene is essential for the maintenance but not the induction of inflammatory pain states and that zif268 can regulate GR in the spinal cord.

Related Products: SP-SAP (Cat. #IT-07)

Kline IV RH, Wiley RG (2006) Role of spinal cord µ-opioid receptor expressing dorsal horn neurons in morphine analgesia. Neuroscience 2006 Abstracts 643.19. Society for Neuroscience, Atlanta, GA.

Summary: The role of spinal cord μ-opioid receptor expressing dorsal horn neurons in morphine analgesia is not clearly understood. Using lumbar intrathecal (i.t.) injections of the targeted toxin dermorphin-saporin to selectively destroy these cells, we sought to determine the effect of this lesion on the antinociceptive activity of systemic and i.t. morphine on the hotplate test. We examined the antinociceptive effects of morphine across a range of stimulus intensities (44, 47 & 52oC) in order to assess responses mediated by C or Aδ thermal nociceptors. Experiment 1 (systemic morphine): Sixteen Sprague Dawley male rats were injected with 500ng dermorphin-saporin i.t. or PBS and hotplate testing resumed one week after injections. Baseline hotplate responses were monitored for three weeks after which systemic morphine dose response curves (0, 2.5, 5, &10 mg/kg s.c.) were performed. Experiment 2 (spinal intrathecal morphine): Twelve Long Evans female rats were surgically implanted with indwelling lumbar i.t. catheters (8.5cm), underwent baseline hotplate testing for 7 days, had i.t. morphine dose response curves (0, 0.01, 0.1, & 1 μg) performed at 44 & 52oC seven days before and eight days after dermorphin-saporin injections. The dependent measures for the hotplate test were: 1) latencies to the first lick or guard response (all temperatures) and 2) the cumulative durations and amounts of licking and guarding events (44 and 47oC). Loss of lamina II MOR-expressing dorsal horn neurons after dermorphin-saporin was confirmed in spinal cord sections from each rat stained for MOR1 and MOR1C using standard immunoperoxidase techniques on adjacent 40 μm sections from the L4 spinal segment. Baseline responses to noxious heat did not decrease after i.t. dermorphin-saporin. The antinociceptive activity of systemic morphine was attenuated in dermorphin-saporin treated rats at 44 & 47oC; this effect was least striking on the 52oC hotplate and greatest on the 44oC hotplate. The dermorphin-saporin-induced lesion reduced the antinociceptive effects of intrathecal morphine more than systemic morphine. Based on the above findings are others not included here, we conclude that dorsal horn MOR expressing neurons are necessary for morphine to exert its maximum antinociceptive and analgesic effects.

Related Products: Dermorphin-SAP / MOR-SAP (Cat. #IT-12)

Miller A, Martinez L, De LaCalle S (2006) Astrocytic reaction to a lesion, under hormonal deprivation. Neuroscience 2006 Abstracts 660.1. Society for Neuroscience, Atlanta, GA.

Summary: The basal forebrain cholinergic system plays an essential role in cortical plasticity and functional recovery following brain injury, although the precise mechanism is not known. Earlier studies from our laboratory have suggested that estrogen may have a protective effect on the basal forebrain cholinergic system, particularly in the maintenance of neuronal architecture. Although there is evidence for direct actions of estrogen on cholinergic neurons in vitro, the contribution of local glial cells to neuronal repair in this cell group, in vivo, has not been documented. We hypothesized that estrogen could also mediate neuronal repair through a modulatory effect on the activation of reactive astrocytes. Young adult female rats (n=28) were used in these studies, 14 were ovariectomized and the rest were left intact. All animals received a unilateral injection of 200 nl of the immunotoxin 192 IgG-saporin into the nucleus of the horizontal limb of the diagonal band of Broca (HDB). One month after the lesion, half of the animals in each group were implanted subcutaneously with a pellet releasing estrogen or placebo (n=7 per group) for 60 days. Using immunocytochemistry with an antibody against glial fibrillary acidic protein (GFAP), a specific marker for astrocytes, we studied changes in the expression of GFAP in the basal forebrain at the end of the treatment. Image analysis of histological sections revealed that GFAP levels in the side of the lesion were slightly higher that in the corresponding contralateral intact side. Overall change in GFAP expression in the ovariectomized animals treated with estrogen was not significantly different from the non-ovariectomized controls. In the ovariectomized animals treated with placebo (therefore undergoing a 3 month estrogen deprivation), levels of GFAP on the lesioned side were 20% higher than in controls. These results suggest that estrogen may prevent activation of astrocytes after a lesion, and perhaps allow a regenerative remodeling process to occur.

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

Brown HD, Kozak R, Sarter M (2006) Bilateral removal of cholinergic inputs to the medial prefrontal cortex disrupts the ability of rats to cope with challenges on attentional performance. Neuroscience 2006 Abstracts 369.20. Society for Neuroscience, Atlanta, GA.

Summary: Studies using microdialysis for the measurement of the release of neurotransmitters in task-performing animals demonstrated attentional performance-associated increases in acetylcholine (ACh) release in the medial prefrontal cortex (mPFC). Moreover, these studies indicated that challenges on attentional performance are associated with augmented increases in mPFC ACh release. Such increases in ACh release were observed while the animals’ performance remained impaired in response to pharmacological or behavioral challenges, and while performance recovered from such challenges. These findings support the general hypothesis that increases in prefrontal cholinergic neurotransmission mediate increases in attentional effort, including the recruitment of prefrontal efferent projections to optimize top-down input processing in sensory and sensory-associational cortical regions. This hypothesis further suggests that cholinergic inputs to these regions directly amplify input processing, and that this more posterior branch of the cortical cholinergic input system is regulated in part by prefrontal outputs (Sarter et al. 2005, 2006). We have previously demonstrated that cortex-wide removal of cholinergic inputs results in persistent impairments in attentional performance. The present experiment was designed to demonstrate that restricted removal of mPFC cholinergic inputs selectively disrupts the animals’ ability to increase their attentional effort in order to maintain and recover from impairments produced by a visual distractor. Animals were trained in a sustained attention task and familiarized with the distractor. Cholinergic inputs to the prelimbic and anterior cingulate cortex were removed by infusions of 192 IgG-saporin into the mPFC. Results indicate that this lesion primarily exaggerated the detrimental performance effects of the distractor. Specifically, the ability of lesioned animals to stabilize their residual hit rate was impaired following distractor presentation. These results indicate that the integrity of cholinergic inputs to the mPFC is necessary for the recruitment of the cognitive mechanisms mediating stabilization and recovery of cognitive performance following attentional challenges.

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

Newman LA (2006) Comparison of the effects of selective cholinergic or noradrenergic deafferentation in the medial, prefrontal cortex on sustained attention. Neuroscience 2006 Abstracts 369.21. Society for Neuroscience, Atlanta, GA.

Summary: Acetylcholine (ACH) and norepinephrine (NE) have been shown to be critically important in controlling the activity of cortical neurons during attention demanding tasks. ACH efflux increases during performance of a sustained attention task and the introduction of distracting stimuli augment this efflux (Himmelheber, Sarter and Bruno 2000). Electrophysiological recordings in NE cell bodies in the locus coeruleus show an increase in tonic firing when distracting stimuli are presented during an attentional task (Aston-Jones and Cohen 2005). The current study assesses the effects of neuroanatomically discrete depletions of these neurotransmitters in the prefrontal cortex (PFC) on a sustained attention task. Male, Long Evans rats received either sham (SHAM), cholinergic (ACH LX) or noradrenergic (NE LX) lesions of the medial wall of the PFC by injections of vehicle, 192 IgG saporin or dopamine beta-hydroxylase saporin respectively. Rats were trained to detect brief, temporally unpredictable, visual cues of varying duration (500, 100, 25 msec) and discriminate these events from non-signal trials. Several manipulations were run to vary the attentional load of the task. These manipulations include a tone with a predictable on-off pattern or a tone with an unpredictable on-off pattern. Preliminary results suggest that NE LX rats were more vulnerable than SHAM or ACH LX rats to the detrimental effects of the unpredictable but not predictable tone. These data suggest that NE is critical to filtering unpredictable distractor stimuli. Additionally we tested the effects of disrupting the temporal contiguity between correct responses and reinforcement as this has previously been shown to increase NE efflux in the frontal cortex. All animals were impaired by the introduction of a variable delay between a correct response and the delivery of a food reinforcer, however NE and ACH lesions of the PFC augmented this impairment. This suggests that both neuromodulators are critical in maintaining performance when reinforcer predictability changes. Manipulations of event rate, event asynchrony, signal probability and the dynamic stimulus range will also be discussed.

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

Pasumarthi RK, Fadel J (2006) Anatomical and neurochemical mediators of nicotine-induced activation of orexin neurons. Neuroscience 2006 Abstracts 369.22. Society for Neuroscience, Atlanta, GA.

Summary: Orexin/hypocretin neurons of the lateral hypothalamus and contiguous perifornical area (LH/PFA) are important for state-dependent behavior and metabolic regulation. These neurons are activated-as indicated by Fos expression-by a variety of psychostimulant drugs including nicotine. Previously, we have shown that acute nicotine-induced activation of orexin neurons can be blocked by either the non-selective nicotinic antagonist mecamylamine or the selective α4β2 antagonist dihydro-beta-erythroidine (DHβE). However, the hypothalamic afferents and neurotransmitters mediating nicotine-elicited activation of orexin neurons remain to be established. Since the LH/PFA is rich in glutamatergic and cholinergic inputs, we performed in vivo microdialysis to determine the effect of both systemic and local nicotine on release of glutamate and acetylcholine (ACh) in this region of the hypothalamus. Local nicotine administration (100 μM; 2.0 mM) increased ACh and glutamate release in the LH/PFA. Furthermore, in a separate experiment, nicotine-elicited Fos expression in orexin neurons was reduced by either ibotenic acid lesions of the prefrontal cortex (PFC), which provides a substantial glutamatergic input to the hypothalamus, or by cholino-selective (192 IgG saporin) lesions of the basal forebrain. Collectively, these data suggest that glutamatergic inputs from the PFC and cholinergic inputs from the basal forebrain may act cooperatively to mediate the effect of acute nicotine on orexin neurons. Neural circuitry linking orexin neurons with the basal forebrain, PFC and PVT is likely to contribute to the effects of nicotine on wakefulness and attention.

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

Frederick-Duus D, Fadel J (2006) Orexin transmission is required for food-related increases in cortical acetylcholine release. Neuroscience 2006 Abstracts 369.23. Society for Neuroscience, Atlanta, GA.

Summary: The hypothalamic orexin/hypocretin neuropeptides (OxA and OxB) are crucial modulators of state-dependent behavior including the regulation of arousal in response to homeostatic challenges. Orexins provide a moderately dense innervation of cholinergic portions of the basal forebrain, including the ventral pallidum/substantia innominata and nucleus basalis magnocellularis. OxA administration in this area also produces robust increases in cortical acetylcholine (ACh) release. Here, we used in vivo microdialysis to test the hypothesis that orexin transmission is required for the increase in cortical ACh release resulting from presentation of stimuli related to palatable food. Rats were mildly food-deprived and trained to associate sudden darkness in the testing room with presentation of sweetened cereal. Stimulated cortical ACh release in these animals was blocked by orexin B-saporin (OxB-SAP) lesions of the perifornical hypothalamus at doses that produced 75-80% loss of orexin neurons, but minimal loss of other neuronal phenotypes in this area. In intact animals, pretreatment with the orexin 1 receptor (Ox1R) antagonist SB334867 similarly abolished food cue-elicited increases in cortical ACh release, indicating the specific involvement of OxA in this phenomenon. Neither OxB-SAP nor SB334867 reduced affected basal ACh release. Finally, in old rats (28-30 months), double-label immunohistochemistry revealed a reduction in orexin-immunoreactive fibers near cholinergic somata and dendrites in the basal forebrain regions, consistent with the deficits in stimulated ACh release seen with old animals in this paradigm. Collectively, these data suggest that phasic orexin activation of the basal forebrain cholinergic system may bias attentional resources toward stimuli related to underlying homeostatic challenges, thus coordinating the processing of interoceptive and exteroceptive cues. Age-related deficits in these capacities may have an orexinergic basis.

Related Products: Orexin-B-SAP (Cat. #IT-20)

Broussard JI, Venugopal S, Sarter M, Givens B (2006) Cholinergic modulation of posterior parietal neuronal activity associated with the detection of signals in attentional task-performing rats. Neuroscience 2006 Abstracts 369.7. Society for Neuroscience, Atlanta, GA.

Summary: The posterior parietal cortex (PPC) is considered a major component of the brains’ attention systems, specifically of the orientation control network. This network controls the selection of stimuli, especially if stimuli are presented at unpredictable or multiple locations. Thus, mechanisms optimizing stimulus detection are hypothesized to represent fundamental components of the processes mediated via neuronal circuitry involving the PPC. Previous studies indicated the role of basal forebrain cholinergic projections to the cortex in the detection of signals. Furthermore, we demonstrated that performance of an attentional task involving signal detection activates PPC neurons in rat, specifically if signals are followed by a behavioral response indicating successful detection. The present experiment was designed to test the hypothesis that signal detection-related activation of PPC neurons depends on the integrity of cholinergic inputs to the PPC. Animals were trained to perform an operant sustained attention task involving signal detection as well as responding to non-signal events. Animals were equipped with a drivable headstage to insert stereotrodes into the PPC. After recording PPC neuronal activity during several baseline sessions, including the effects of a distractor, cholinergic projections to the PPC were lesioned by infusing 192 IgG-saporin into the recording region. Recordings from control animals prior to and after saline infusions (599 neurons total) indicate that PPC neurons (56 %) display increases in single unit activity evoked by detected visual signals. Presentation of a visual distractor reduced the number of signal detections but did not alter the detection-associated firing characteristics of PPC neurons, and relatively few neurons were modulated by the onset or offset of the distractor (8%). Unilateral, restricted removal of cholinergic inputs to the PPC did not affect the animals’ detection rate but reduced the proportion of neurons showing detection-related increases in neuronal activity (27 %). These data support the hypothesis that cholinergic inputs to the PPC mediates the detection of signals and thus contributes to the fundamental attentional processing mediated via PPC circuitry.

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