sfn2005

Fargo KN, Sengelaub DR (2005) Testosterone treatment prevents deficits in motor activation caused by partial loss of motoneurons. Neuroscience 2005 Abstracts 672.8. Society for Neuroscience, Washington, DC.

Summary: In male rats, motoneurons of the spinal nucleus of the bulbocavernosus (SNB) project to the bulbocavernosus and levator ani muscles (BC/LA). The SNB system is dependent on androgens for its development, adult morphology, and function. We have previously demonstrated that unilateral depletion of SNB motoneurons induces atrophy of dendrites and somata in contralateral SNB motoneurons, and that this atrophy is prevented by treatment with exogenous testosterone. In the present experiment, we tested the hypothesis that this neuroprotective effect of testosterone on the morphology of SNB motoneurons is accompanied by a neuroprotective effect on the electrophysiological function of the system. We unilaterally depleted right-side SNB motoneurons by intramuscular injection of cholera toxin-conjugated saporin. Simultaneously, some of the saporin-injected rats were castrated and immediately given exogenous testosterone in subcutaneous Silastic capsules designed to produce testosterone titers in the high-normal physiological range. Four weeks later, animals were anesthetized and spinally transected. A stimulating electrode was placed on the left L6 dorsal root, which carries motor afferents from the BC/LA, and a recording electrode was placed on the motor branch of the left pudendal nerve, which carries SNB motoneuron axons to the BC/LA. Both nerves were then severed distal to electrode placement, and recruitment curves were generated by stimulating through the entire range of effective intensities. Consistent with our previously reported morphological changes, unilateral motoneuron depletion resulted in an attenuation of the recruitment of motoneurons in the contralateral SNB, and this was completely prevented by treatment with exogenous testosterone. This result provides a functional correlate to the neuroprotective effects of testosterone treatment on SNB morphology following unilateral motoneuron depletion, further supporting a role for testosterone as a neurotherapeutic agent in the injured nervous system.

Related Products: CTB-SAP (Cat. #IT-14)

Fraley GS (2005) Immunolesions of glucoresponsive projections to the arcuate nucleus alter glucoprivic feeding and luteinizing hormone secretion but not sex behavior in adult male rats. Neuroscience 2005 Abstracts 758.7. Society for Neuroscience, Washington, DC.

Summary: Metabolic signals such as insulin, leptin and glucose are known to alter hypothalamic function. Although insulin and leptin are known to directly alter hypothalamic areas that regulate reproduction, the mechanisms by which glucose alters reproductive function are not as clear. Catecholaminergic neurons in the A1/C1 region of the hindbrain are glucose-responsive and project to the arcuate nucleus. To determine if this pathway is involved in the regulation of sex behavior and luteinizing hormone (LH) secretion, this catecholamingergic pathway was lesioned by injecting saporin conjugated to anti-dopamine-β-hydroxalase (DSAP) or unconjugated saporin (SAP) into the arcuate nucleus of adult male rats. Rats were given glucoprivic challenges then feeding and sex behaviors were observed. As was expected, the DSAP treated rats showed a significant decreased in feeding during glucoprivation (250 mg/kg 2-deoxy-D-glucose, 2DG) compared to SAP controls (p < 0.05). Glucoprivation caused a significant reduction in sex behavior (p < 0.05) in both SAP and DSAP animals equally, compared to saline treatments in either treatment group. At the end of the experiment, animals were given a final challenge with 2DG or saline, killed by decapitation and trunk blood was assayed for plasma LH levels. In SAP animals, 2DG elicited a significant decrease in plasma LH levels (p < 0.05). However, in DSAP animals there was a significant increase (p < 0.05) in plasma LH levels compared to saline-treated rats. These data indicate that the A1/C1 efferents to the ventromedial hypothalamus are involved in the glucostatic regulation of feeding behavior and LH secretion, but not sex behavior in the adult male rat.

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

Vijayakumar S, Masood A, Smith M, Clark JP, Nelson DE, Ding JM (2005) Immunolesion of p75 NGF receptor in the mouse SCN attenuated light-induced phase shift of the circadian wheel-running rhythm. Neuroscience 2005 Abstracts 766.18. Society for Neuroscience, Washington, DC.

Summary: Mammalian circadian rhythms are regulated by the suprachiasmatic nucleus (SCN) of the hypothalamus. Alhough the SCN can orchestrate these rhythms in the absence of external cues, it is entrained to environmental cycles through the retinohypothalamic tract. Light-induced phase shifts in circadian rhythm is a classic example of short-term environmental stimuli inducing lasting changes in intracellular signals and gene expression within the SCN cells that alter the phase of the SCN pacemaker and allow entraiment. Since neurotrophins are known to mediate neural plasticity, we investigated the role of brain-derived neurotrophic factor (BDNF) on resetting the phase of the SCN both in vitro and in vivo. We used the SCN brain slice model to study the direct effect of BDNF on the circadian rhythm. Briefly, coronal hypothalamic slices containing the SCN were prepared using 129B/6 mice. The circadian rhythm of the SCN neurons in the brain slice was monitored for 2-3 days by continuously sampling the spike frequencies with single-unit extracellular electrodes. Brief microdrop applications of BDNF (10 uM) induced robust phase delays at CT 16 and phase advances at CT 22. BDNF binds to neurotrophin receptors, including the low affinity p75NTR, which is localized in the SCN. When the toxin Saporin is conjugated to the antibody against p75NTR, it selectively destroys the cells expressing the p75NTR. Three weeks after the stereotaxic injection of the mu p75-Saporin (Advanced Targeting System) into the third ventricle (1 ul over 20 min), the p75NTR immunoreactivity in the mouse SCN is abolished. Immunolesion of the p75NTR in the SCN attenuated light-induced phase delays of the wheel running rhythm at CT16. Consistent with previous findings, our results support a role for BDNF and its receptor p75NTR, in resetting the circadian rhythm of the SCN in mice.

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

Greene DM, Castillo MR, Alexander KA, McMahan A, Raap DK, Bult-Ito A (2005) Neurotoxic lesions of serotonin cells in the dorsal raphe reduce compulsive-like nest building in mice. Neuroscience 2005 Abstracts 796.10. Society for Neuroscience, Washington, DC.

Summary: Bi-directional selection for thermoregulatory nest-building behavior in house mice (Mus musculus) has resulted in a 40-fold difference in the amount of cotton used for nest-building between the high and the low selected lines (big and small nest-builders, respectively). The efficacy of serotonin re-uptake inhibitors (SSRIs), especially fluoxetine, for the treatment of obsessive-compulsive disorder (OCD) indicates a serotonergic involvement in the disorder. The repetitive nest-building behavior, characteristic of the big nest-builders, is a compulsive-like behavior that is responsive to SSRI treatment. We investigated the functional involvement of serotonergic pathways in excessive, repetitive nest-building behavior in mice by lesioning serotonergic cells in the dorsal raphe using the neurotoxin 5,7-dihydroxytryptamine (5,7-DHT) or SERT-saporin (Advanced Targeting Systems). 5,7-DHT lesioned mice had a significant decrease in the number of serotonin-stained cells in the dorsal raphe. No decrease was noted in serotonin staining after lesions performed with the SERT-saporin neurotoxin. Mice with successful 5,7-DHT lesions also significantly decreased compulsive-like nest-building as compared to sham and non-surgery controls. These data taken together with additional findings in these mice support the involvement of serotonin pathways in OCD. This data further supports the big nest-builders as a potentially valuable animal model of compulsive behaviors in humans and a means to more clearly identify neurobiological pathways involved in OCD.

Related Products: Anti-SERT-SAP (Cat. #IT-23)

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)

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.

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

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)