sfn2005

Truitt WA, Oberlin BG, Dietrich AD, Fitz SD, Shekhar A (2005) Neurokinin 1 receptor containing interneurons of the BLA are putative candidates for the inhibitory component of feed-forward inhibition from the mPFC to the BLA. Neuroscience 2005 Abstracts 796.12. Society for Neuroscience, Washington, DC.

Summary: The amygdala and in particular the basolateral nucleus of the amygdala (BLA) is a central site for fear and anxiety. The BLA is under tonic inhibition by a network of inhibitory interneurons. Additionally, cortical inputs can both excite or inhibit the output of the BLA, resulting in increases or decreases in anxiety/fear-like behaviors. In particular mPFC inputs to the BLA can suppress BLA output and inhibit fear conditioning. However, the mechanism by which this occurs is not fully understood. Evidence from electrophysiological studies suggests a feed forward inhibitory relationship between the mPFC and the BLA. This feed forward inhibition putatively occurs by mPFC-glutamatergic inputs exciting GABAergic interneurons of the BLA, which in turn suppress firing of the BLA projection neurons. However, tracing studies demonstrate that the vast majority of mPFC inputs to the BLA form synapses with dendritic spines, which have been reported to exist only on projection neurons of the BLA. Here we present data that suggests a specific subclass of BLA interneurons, those that express neurokinin 1 receptors (NK-1r) are likely candidates for the inhibitory component of the feed forward inhibition described above. Here we report that, in the rat, the NK-1r containing BLA-interneurons contain dendritic spines and NMDA receptors. Furthermore, we report that in anesthetized rats disinhibition of mPFC neurons by injections of bicuculline methiodide (50 pmol), leads to cFos induction in 25 – 50% of the NK-1r containing interneurons in the BLA, while 0% of the NK-1r interneurons expressed cFos following vehicle injections. Furthermore, selective ablation of these NK-1r containing BLA-interneurons (by use of the targeted toxin, SSP-Saporin) suppressed anxiolytic-like effects of familiarity in the SI test. Collectively, these data suggest the NK-1r containing interneurons of the BLA may respond to glutamatergic inputs from the mPFC and may be involved in a mPFC-BLA anxiety or fear regulating pathway.

Related Products: SSP-SAP (Cat. #IT-11)

Datta S, Kline IV RH, Wiley RG (2005) Increased formalin behavior after selective destruction of μ opiate receptor-expressing dorsal horn neurons: impaired descending analgesic control?. Neuroscience 2005 Abstracts 623.15. Society for Neuroscience, Washington, DC.

Summary: Spinal intrathecal injection of dermorphin-saporin (derm-sap) selectively destroys dorsal horn neurons expressing the mu-opiate receptor (MOR). In the present study, we sought to determine the effect of derm-sap (500 ng, i.t.) on responses to intraplantar formalin injection (25 ul of 5%). After formalin injection, rats were immediately placed into a clear observation chamber with a video camera beneath the floor. Rats were videotaped for 90 minutes and their behavior scored offline for one minute out of every 5 minutes. 120 minutes after formalin injection rats were anesthetized with pentobarbital and perfused with formalin. Spinal cord sections were stained for MOR and cholecystokinin (CCK) using standard immunoperoxidase techniques on adjacent 40 um sections from L4 spinal segment. Coded sections were used to assess MOR staining intensity by quantitative densitometry. Derm-sap treated rats showed no separation between phase I and II and spent more time than vehicle controls licking/guarding/biting the injected hindpaw during both phase I and II. Derm-sap significantly decreased dorsal horn MOR. Staining for CCK showed time dependant changes after derm-sap which was not present in PBS controls. These same derm-sap treated rats performed normally on hotplate at 44, 47 and 52 C and had normal analgesic responses to systemic morphine on 44, 47 and 52 C hotplates. We interpret these data to indicate that loss of the dorsal horn MOR-expressing neurons reduces the effect of descending analgesic mechanisms. Supported by NIH R21-DA14380 and Department of Veterans Affairs.

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

Vera-Portocarrero LP, Xie Y, King T, Lai J, Porreca F (2005) Facilitatory influences from the rostral ventromedial medulla (RVM) are required for pancreatic nociception. Neuroscience 2005 Abstracts 623.18. Society for Neuroscience, Washington, DC.

Summary: Pain is a frequent complaint of patients with pancreatitis or pancreatic cancer. An animal model of pancreatitis induced by dibutyltin dichloride (DBTC) is characterized by abdominal hypersensitivity to mechanical stimuli that appears by day 3 after induction of pancreatitis and persists for at least 10 days. We have used this model to evaluate the role of descending pain modulatory pathways from the RVM in the processing of visceral pain. Pancreatitis was induced in rats by a single tail vein injection of DBTC. Animals were monitored for mechanical sensitivity of the abdominal area as an index of pancreatic nociception using von Frey hairs applied to the surface of the abdomen and recording the frequency of withdrawals from stimulation. Six days after DBTC injection, when mechanical hypersensitivity was fully developed, lidocaine, or saline, was microinjected into the RVM. Lidocaine, but not saline, given into the RVM produced a time-related reversal of mechanical hypersensitivity which peaked by 20 min after injection in animals with pancreatitis. RVM lidocaine had no effect on rats without pancreatitis. A second group of rats received a single microinjection of the cytotoxin dermorphin-saporin into the RVM in order to ablate mu opioid receptor expressing cells that have been proposed to drive descending pain facilitation. 28 days later, the rats received DBTC and their response to mechanical stimulation was monitored daily. These rats showed mechanical hypersensitivity on day 3 after DBTC, but the sensory threshold reverted to normal level by day 6, while rats that had been pretreated with dermorphin, saporin, or water exhibited persistent mechanical hypersensitivity after DBTC out to day 10. These data suggest that a blockade of the descending input from the RVM by lidocaine is sufficient to block the pancreatitis-induced visceral pain, and that the mu opioid receptor expressing cells in the RVM are critical for the persistent pain state.

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

Kozak R, Parikh V, Martinez V, Brown H, Bruno JP, Sarter S (2005) What does acetylcholine do in the posterior parietal cortex (PPC)? Attentional performance-associated increases in PPC ACh efflux. Neuroscience 2005 Abstracts 644.1. Society for Neuroscience, Washington, DC.

Summary: Medial prefrontal cortex (mPFC) ACh efflux has been demonstrated to mediate attentional performance, particularly under conditions that require increases in attentional effort or the processing of distractors. Activation of the mPFC, in part as a result of cholinergic activity, is thought to orchestrate top-down effects for optimization of input processing elsewhere in the cortex. We previously demonstrated that mPFC cholinergic mechanisms influence PPC ACh efflux, suggesting that PPC ACh efflux is a component of the prefrontal circuitry mediating top-down effects. The present experiment was designed to characterize attentional performance-associated increases in PPC ACh efflux in animals performing a regular sustained attention task, following the presentation of a visual distractor, and following loss of cholinergic inputs to the mPFC. Attention task-performing animals were equipped with a guide cannula for insertion of a microdialysis probe and to collect dialysates in the PPC. Cholinergic projections to the mPFC were lesioned bilaterally by infusing 192-IgG saporin into the mPFC. Regular attentional performance was associated with increases in PPC ACh efflux that mirrored those observed previously in the mPFC. In contrast to evidence indicating a cholinergic role in the processing of distractors in the mPFC, PPC ACh efflux was not affected by the distractor and associated impairments in performance. The performance effects of the distractor were augmented in animals with mPFC cholinergic deafferentation. Performance-associated increases in PPC ACh efflux of deafferented animals were higher following the presentation of the distractor than in intact rats. These data support the hypotheses that mPFC cholinergic inputs contribute to the suppression of the effects of distractors and to the recruitment of posterior cortical cholinergic inputs to optimize processing under challenging conditions.

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

Butt AE, Cabrera S, Chavez C, Corley S, Cortez A, Figueroa J, Kitto M, Torner E (2005) Basal forebrain cholinergic lesions produce a dissociation of impairment in delay and trace conditioning in rats. Neuroscience 2005 Abstracts 644.2. Society for Neuroscience, Washington, DC.

Summary: Recent research suggests that Pavlovian trace conditioning, but not delay conditioning, requires awareness or attention, where these processes appear to depend on specific brain systems. For example, Clark, Manns, and Squire (2002) have 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. Han and colleagues (2003) have shown that the anterior cingulate cortex (ACC) is similarly necessary for trace but not delay conditioning in rats. The medial prefrontal cortex (mPFC) is also involved in trace but not delay conditioning (Kronforst-Collins & Disterhoft, 1998). The basal forebrain cholinergic system (BFCS) has projections to 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 appetitive conditioning in rats. Rats received bilateral injections of SAP or saline only (control group) into BFCS prior to conditioning with a tone CS and sucrose pellet US in either a delay or 10 s trace conditioning paradigm. Preliminary results support this hypothesis. Compared to controls, rats in the BFCS lesion group showed moderate impairment in delay conditioning but more severe impairment in the trace conditioning paradigm. Rats in both groups showed an increase in differential responding to the CS in the delay paradigm, although the BFCS lesion group showed less conditioned responding than controls. In contrast, only the controls showed progressive differential responding to the CS in the trace conditioning paradigm. These data suggest that the BFCS contribute critically to the maintenance of attention in Pavlovian trace conditioning.

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

Strait TA, Montoya D, Pang KCH (2005) Role of the medial septum in a repeated acquisition task. Neuroscience 2005 Abstracts 647.14. Society for Neuroscience, Washington, DC.

Summary: The medial septum/diagonal band of Broca (MSDB) provides a major afferent pathway to the hippocampus and both regions are important in learning and memory. The two major projection cells of the MSDB are cholinergic and GABAergic neurons. Although nonselective lesions of the MSDB impair spatial memory, the role of the different MSDB neuronal population in memory is an active area of research. In the present study, rats with preferential cholinergic or GABAergic lesions of the MSDB will be tested on the repeated acquisition task. The task assesses how well a rat can learn the location of a reward that changes from day to day. All sessions are performed on an 8-arm radial arm maze using one arm for reward. Each daily session consists of 5 trials with rats starting from a different arm on each trial. Rats are tested for a total of 9 days; each day a new rewarded arm is used. Our preliminary data suggest that rats with selective cholinergic lesions using 192-IgG saporin are not impaired in acquisition of the task. These results with selective cholinergic lesions contrast with our previous work showing that preferential GABAergic MSDB lesions impair performance of a repeated acquisition task in a water maze. We are currently investigating the effects of preferential GABAergic MSDB lesions on this task. Our preliminary data suggests that cholinergic and GABAergic MSDB neurons may have differential roles in acquisition of a spatial memory task.

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

Lohals R, Veng LM (2005) Cholinergic therapy does not rescue spatial learning deficits induced by ICV injection of 192 IgG-saporin. Neuroscience 2005 Abstracts 653.5. Society for Neuroscience, Washington, DC.

Summary: The cholinergic hypothesis states that central cholinergic dysfunction is responsible for age-dependent cognitive decline. To model this in rats, we induced cholinergic basal forebrain loss the neurotoxin IgG192-saporin (SAP). Following ICV infusion of 2.5 or 5 microgram (ug) SAP, or saline, rats were tested in the radial 12-arm water maze (RAWM), a spatial learning and memory task. While saline sham or 2.5 ug SAP lesioned rats showed normal learning over 4 trials in the RAWM, 5 ug SAP rats were impaired. However, when trained over 20 trials, 5 ug SAP rats eventually attained the same level of performance as 2.5 ug SAP or saline sham rats, and 28 days later all rats showed intact memory for this platform location. In the open field, 5 ug SAP rats failed to habituate. However, SAP or saline sham lesioned rats did not differ in basal activity, rotarod, or visually cued RAWM performance. SAP lesion resulted in severe depletion of ChAT activity in hippocampus and cortex, which significantly correlated with learning impairment in the RAWM. In a second experiment, we used 5 ug ICV SAP to investigate the effect of cholinergic therapy on SAP-induced spatial learning deficits in the RAWM. However, neither galantamine (0.30, 1.25, 5.0 mg/kg) nor RJR-2403 (0.08, 0.31, 1.25 mg/kg) could reverse the SAP induced deficit in RAWM learning. In conclusion, we found that spatial learning in the RAWM was consistently impaired following severe (5.0 ug SAP) cholinergic basal forebrain lesion in rats. This learning deficit was not confounded by general behavioral disturbances. However, with excessive training SAP lesioned rats could learn and later recall spatial information, suggesting that recall is intact in cholinergic lesioned animals. Severe SAP lesion also impaired habituation in an open field and this was not due to hyperactivity. Finally, treatment with galantamine and RJR-2403 did not alleviate the cognitive deficit induced by the SAP lesion, likely due to the severity of cholinergic depletion.

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

Zhang W, Gardell SE, Xie Y, Luo M, Rance NE, Vanderah TW, Porreca F, Lai J (2005) Pain facilitatory cells in the rostral ventromedial medulla coexpress opioid-μ receptors and cholecystokinin type 2 receptors. Neuroscience 2005 Abstracts 394.17. Society for Neuroscience, Washington, DC.

Summary: Pain transmission can be modulated by descending input to the spinal dorsal horn from the rostral ventromedial medulla (RVM). RVM neurons that facilitate nociception are termed “ON-cells”, which are inhibited by mu-opioids, suggesting that they express opioid mu receptors (MOR). Focal application of cholecystokinin (CCK8(s)) into the RVM elicits acute thermal and tactile hypersensitivity and induces ON-cell activity. In situ hybridization using riboprobes for either rat MOR or rat cholecystokinin type-2 receptor (CCK-2) confirms the expression of these receptors in the RVM. Pretreatment with a toxin conjugate, CCK8(s)-saporin results in a significant loss of CCK-2 positive cells in the RVM, concomitant with a blockade of CCK8(s) induced hyperalgesia. The pretreatment also significantly reduces the number of neurons labeled for MOR in the RVM, suggesting that MOR and CCK-2 may be co-localized in some RVM cells. Consistent with these data, similar pretreatment with the toxin conjugate, dermorphin-saporin, which selectively targets MOR expressing neurons, significantly reduces the number of MOR labeled cells in the RVM, blocks RVM CCK8(s) induced hyperalgesia and reduces the number of CCK-2 positive cells in the RVM. In situ hybridization using 35S-labeled CCK-2 riboprobes and Digoxigenin-labeled MOR riboprobes shows that over 80% of labeled RVM neurons co-express both MOR and CCK-2, ~15% express only CCK-2, and very few cells express only MOR. These findings represent the first direct demonstration of the phenotype of pain facilitatory neurons in the RVM. Together with previous studies showing that RVM CCK-2 antagonists reverse nerve injury-induced pain, this phenotype provides strong support for the view that endogenous CCK is a critical mediator of the descending pain facilitation, particularly in the maintenance of experimental neuropathic pain. Support Contributed By: NIDCR R01 DE016458

Related Products: Dermorphin-SAP / MOR-SAP (Cat. #IT-12), CCK-SAP (Cat. #IT-31)

ATS Poster of the Year Winner

Vander Schaaf EB, Lusk JD, Jarrard LE, I’Anson H (2005) Immunotoxic destruction of catecholaminergic pathways disrupts the onset of puberty in the female rat. Neuroscience 2005 Abstracts 406.10. Society for Neuroscience, Washington, DC.

Summary: Ascending catecholaminergic (NE/E) pathways from the brainstem terminate near gonadotropin releasing hormone cell bodies and terminals in the hypothalamus. To determine the significance of NE/E pathways in regulating puberty onset, a neurotoxin (dopamine-ß-hydroxylase conjugated to saporin, DSAP) was administered intracerebrally to developing female rats to destroy this pathway and the timing of puberty onset was monitored. DSAP or vehicle (unconjugated saporin, SAP) was injected into the hypothalamic paraventricular nucleus on Days 23-25 of age (n=10 per group). An additional 8 rats served as untreated controls. Growth rate was monitored daily and on surgery days SAP & DSAP rats grew at a slower rate than controls. Thus, food intake of control rats was temporarily adjusted to ensure that growth rate was similar between groups. Onset of puberty and cycle length were monitored via vaginal cytology. 2-Deoxy-D-glucose-induced glucoprivation determined which rats received complete DSAP lesions, since lesioned rats do not acutely increase food intake when glucose-deprived. Results showed that NE/E neurons were adequately lesioned in seven of ten DSAP rats. Puberty onset (time of first estrus) was delayed in DSAP-lesioned rats (40.86 ± 1.79 days of age, n=7) compared to vehicle or control rats (36.25 ± 0.31 days of age, n=10; 37.50 ± 0.31 days of age, n=8). Estrous cycle length of DSAP rats (5.38 ± 0.46 days, n=7) was not significantly longer than in vehicle or control rats (4.91 ± 0.18 days, n=10; 4.40 ± 0.12 days, n=8). Thus, lesioning the NE/E pathway caused delay in onset of puberty in female rats, but no significant change in estrous cycle length. Therefore, ascending catecholaminergic pathways from the brainstem are important in determining puberty onset timing. First estrus did eventually occur in DSAP rats, suggesting that other neural pathways may be activated to regulate puberty onset and estrous cyclicity in its absence.

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Maddux JM, Chatterjee S, Kerfoot EC, Holland PC (2005) Distinct roles for amygdala central nucleus, medial prefrontal cortex, and posterior parietal cortex in attention for learning and action. Neuroscience 2005 Abstracts 411.16. Society for Neuroscience, Washington, DC.

Summary: Many theories of associative learning claim that the accuracy with which an event predicts its consequences affects the allocation of attention to that event. More reliable predictors are more likely to control action, but less reliable predictors often are more likely to capture attention for purposes of new learning about those events. Previous studies from our lab showed the amygdala central nucleus (ACe) to be important for both sustained attention guiding performance to predictive cues, and for enhanced new learning about less predictive cues. This study investigated the possibility that ACe affects these distinct aspects of attention by influencing different, specialized cortical regions, via its modulation of the basal forebrain cholinergic system. Rats were given either ibotenic acid lesions of ACe, 192 IgG-saporin lesions that reduced the basal forebrain cholinergic input to medial prefrontal cortex (mPFC) or posterior parietal cortex (PPC), or sham lesions of one of these regions. In an operant 5-choice reaction time task, responding to “CRF” ports was reinforced on 100% of the trials, whereas responding to “PRF” ports was reinforced on only 50% of such trials. Later, the ability of one CRF port and one PRF port to overshadow Pavlovian conditioning of auditory cues when port + tone compounds were paired with the delivery of a new, more valued reinforcer was examined. ACe lesions interfered with attention to the PRF cue for both learning and action, whereas reduction of cholinergic input to mPFC interfered only with attention for action, and reduction of cholinergic input to PPC interfered only with attention for new learning. The PRF port overshadowed conditioning of the tone significantly more than did the CRF port in both sham and mPFC rats, but not in ACe or PPC rats. By contrast, relative to CRF port responding, control of port-directed responding by the PRF cue was significantly greater in sham and PPC rats than in ACe or mPFC rats.

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