References

Gray PA, Vandunk C (2007) Developmental origins of ventral medullary NK1r neurons. Neuroscience 2007 Abstracts 187.15/SS7. Society for Neuroscience, San Diego, CA.

Summary: Breathing is a fundamental neural behavior generated by neurons within the brainstem. In the adult rat, bilateral injection of substance P conjugated to saporin (SSP) in the preBötzinger Complex (preBötC) eliminates normal breathing. Unilateral injection produces sleep disordered breathing and eliminates the effects of excitatory amino acid injection on breathing and blood pressure. SSP injection in the RTN region, in contrast, blunts chemosensitivity. The extent these different effects are due to ablation of anatomically, functionally, or genetically distinct populations are unknown. Further, the extent NK1R expression identifies unique populations in neonatal mice is unknown. Transcription factors are fundamental to determining the properties of neurons and it has been proposed a “combinatorial code” of transcription factor expression defines each distinct functional population. From a genome-scale analysis of over 1000 transcription factors and transcriptional co-factors we identified several genes expressed in respiratory regions of the brainstem. Using immunohistochemistry, we analyzed gene expression patterns of NK1R expressing neurons of the ventral medulla in embryonic and neonatal mice. We find there are at least four genetically distinct, partially overlapping populations of NK1R expressing neurons in the ventral medulla. These differ in the transcription factors they express, their onset of NK1R expression, and their co-expression of peptides and g-protein coupled receptors. At the level of the preBötC, there are two populations of NK1R expressing neurons derived from distinct developmental progenitor populations. One population corresponds to the preBötC as defined in rats and co-expresses the peptide somatostatin. A second population is continuous with, and genetically identical to the subCVLM population important for respiratory-cardiovascular coordination. Both populations co-express the somatostatin 2a receptor (SST2aR). At the level of the RTN/pFRG, there are also two populations of NK1R expressing neurons that are derived from similar developmental precursors as the preBötC. Neither of these populations expresses SST2aR. Whether either of these populations corresponds to the RTN or pFRG is currently unknown. These data suggest both the preBötC and RTN/pFRG regions contain developmentally related NK1R expressing populations. Further, they identify the developmental origin of preBötC neurons known to be essential for normal breathing and provide a foundation for understanding the genetic origin of an important neural circuit.

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Radley JJ, Sawchenko PE (2007) Noradrenergic denervation of dorsal medial prefrontal cortex (mPFC) modulates paraventricular hypothalamic responses to acute restraint stress. Neuroscience 2007 Abstracts 198.4/ZZ13. Society for Neuroscience, San Diego, CA.

Summary: The dorsal mPFC is implicated in restricting the hypothalamo-pituitary-adrenal (HPA) axis response to acute emotional stress via its influence on neuroendocrine effector mechanisms represented in the paraventricular hypothalamic nucleus (PVH). The afferents that provide for mPFC engagement during stress may include ascending noradrenergic projections from the locus coeruleus (LC), which are known to be stress-responsive and capable of modulating attentional mechanisms and other aspects of mPFC function. Arguing against such a role for LC-mPFC projections is evidence that LC lesions attenuate PVH/HPA responses to acute emotional stress. Here we sought to clarify the role of the noradrenergic innervation of mPFC in acute stress-induced PVH activation. Rats received injections of the axonally transported catecholamine immunotoxin, anti-dopamine-β-hydroxylase (DBH)-saporin, centered in the prelimbic area, or sham injections of IgG-saporin or saline. 14 days later, rats were subjected to 30 min of restraint and perfused 2 h later. Immunohistochemical localization of the immediate-early gene product, Fos, was employed as an index of cellular activation in PVH. Cell counts revealed that acute stress reliably provoked marked increases in the number of Fos-labeled neurons in the PVH of all restrained groups relative to unstressed controls. Among stressed groups, anti-DBH-saporin lesions in the dorsal mPFC decreased activational responses in the PVH by 30%, relative to sham-lesioned animals, that were focused in the hypophysiotropic (dorsal medial parvocellular) subdivision. DBH immunostaining revealed a virtually complete noradrenergic denervation of the prelimbic area in immunotoxin-treated animals, while the ventral mPFC (infralimbic area) remained intact. Cortical fields dorsally and laterally adjoining the target area displayed a partial denervation, consistent with local collateralization of prelimbic-projecting LC neurons. While these data are consistent with a role for LC-mPFC projections in facilitating restraint-induced PVH engagement, it remains to be determined how this perspective may be reconciled with prior evidence indicating that mPFC serves normally to inhibit PVH/HPA responses to acute emotional stress.

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

Sparrow AW, Lowery EG, Thiele TE (2007) Amygdalar neuropeptide Y (NPY) signaling modulates stress-induced reductions of food intake in Balb/cJ mice. Neuroscience 2007 Abstracts 270.10/X24. Society for Neuroscience, San Diego, CA.

Summary: The existing literature suggests that NPY signaling in the amygdala modulates anxiety-like behaviors and ethanol consumption in rodents, but does not modulate food intake. On the other hand, NPY signaling within the hypothalamus controls food intake but does not influence anxiety-like behavior. Based on these observations, the current study tested the hypothesis that attenuation of NPY signaling within the amygdala would increase anxiety-like behavior and augment stress-induced increases of ethanol consumption while at the same time have no effect of feeding behavior. To address this hypothesis, male Balb/cJ were given bilateral injection (48 ng/5-min/side) into the central nucleus of the amygdala (CeA) of NPY conjugated to the neurotoxin saporin (NPY-SAP) or saporin alone (Blank-SAP). NPY-SAP is a ribosome inactivating neurotoxin that targets and kills cells expressing NPY receptors. After recovery, mice were first tested for anxiety-like behavior using the zero maze test. They were then given access to 8% (v/v) ethanol versus water in a two-bottle test. After ethanol intake stabilized, half the NPY-SAP and Blank-SAP mice were subjected to a 5-min forced swim stress sessions, once a day over 5-days. Ethanol, water and food consumption were measured for 4-weeks following the forced swim procedures. At the end of the experiment, ethanol was removed for two-weeks and all mice were given a 24-hour open-field locomotor activity test. The results showed that mice treated with NPY-SAP in the CeA spent significantly less time in the open portion of the zero maze reflecting elevated anxiety-like behavior. Contrary to predictions, neither neurotoxin treatment nor stress condition altered ethanol intake. Interestingly, NPY-SAP treated mice that experienced forced swim stress consumed significantly less food than non-stressed NPY-SAP treated mice and stress and non-stressed mice treated with the Blank-SAP. Reduced feeding by NPY-SAP stressed mice was not associated with reduced body weight, suggesting possible alterations of energy metabolism. Further, reduced feeding was not attributable to reductions of activity. This study provides novel evidence that amygdalar NPY signaling modulates feeding/energy balance in mice with a history of stress exposure.

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Hains BC, Zhao P, Waxman S (2007) ERK1/2 regulates microglia-neuron signaling and pain by PGE2 following SCI. Neuroscience 2007 Abstracts 287.16/LL14. Society for Neuroscience, San Diego, CA.

Summary: We recently showed that microglia become activated after experimental SCI and dynamically maintain hyperresponsiveness of spinal cord nociceptive neurons and pain-related behaviors. Mechanisms of signaling between microglia and neurons that help to maintain abnormal pain processing are unknown. In this study, adult male Sprague Dawley rats underwent T9 spinal cord contusion injury. Four weeks after injury when lumbar dorsal horn multireceptive neurons became hyperresponsive and when behavioral nociceptive thresholds to mechanical and thermal stimuli were decreased, we tested the hypothesis that prostaglandin E2 (PGE2) contributes to signaling between microglia and neurons. Immunohistochemical data showed specific localization of phosphorylated extracellular signal-regulated kinase 1/2 (pERK1/2), an upstream regulator of PGE2 release, to microglial cells and a neuronal localization of the PGE2 receptor E-prostanoid 2 (EP2). Enzyme immunoassay analysis showed that PGE2 release was dependent on microglial activation and ERK1/2 phosphorylation. Pharmacological antagonism of PGE2 release was achieved with the mitogen-activated protein kinase kinase 1/2 (MEK1/2) inhibitor PD98059 and the microglial inhibitor minocycline. Cyclooxygenase-2 expression in microglia was similarly reduced by MEK1/2 inhibition. PD98059 and EP2 receptor blockade with AH6809 resulted in a decrease in hyperresponsiveness of dorsal horn neurons and partial restoration of behavioral nociceptive thresholds. Selective targeting of dorsal horn microglia with the Mac-1-SAP immunotoxin resulted in reduced microglia staining, reduction in PGE2 levels, and reversed pain-related behaviors. On the basis of these observations, we propose a PGE2-dependent, ERK1/2-regulated microglia-neuron signaling pathway that mediates the microglial component of pain maintenance after injury to the spinal cord.

Related Products: Mac-1-SAP rat (Cat. #IT-33)

Coons KD, Wilson RE, Sengelaub DR (2007) Protection from dendritic atrophy with testosterone following partial motoneuron depletion: dose-dependence in males and efficacy in females. Neuroscience 2007 Abstracts 56.11/S5. Society for Neuroscience, San Diego, CA.

Summary: Partial depletion of motoneurons from the highly androgen-sensitive spinal nucleus of the bulbocavernosus (SNB), or the more typical somatic motoneuron population innervating the quadriceps muscles, induces dendritic atrophy in remaining motoneurons. Treatment with testosterone (T) is neuroprotective, and dendritic atrophy following partial motoneuron depletion is attenuated in both populations. In the present study, we examined the dose-dependency of T effects in male rats, as well as its potential efficacy in females. Motoneurons innervating the bulbocavernosus/levator ani (BC/LA) or vastus medialis muscles were selectively killed by intramuscular injection of cholera toxin-conjugated saporin. Simultaneously, saporin-injected rats were given T implants designed to produce plasma titers ranging from 0.75 to 5.0 ng/ml or left untreated. Four weeks later, motoneurons innervating the contralateral BC or the ipsilateral vastus lateralis muscles were labeled with cholera toxin-conjugated HRP, and dendritic arbors were reconstructed in 3 dimensions. Partial motoneuron depletion resulted in dendritic atrophy in remaining SNB and quadriceps motoneurons (40% and 36% of normal length, respectively). T treatment attenuated this atrophy in a dose-dependent manner, with maximum effectiveness at 2.0-2.5 ng/ml (the normal adult physiological level). This dosage of T resulted in SNB dendritic lengths that did not differ from those of intact control males. In contrast, although dendritic atrophy in quadriceps motoneurons was attenuated by the same dosage of T, resultant dendritic lengths were 60% of normal length, and did not improve further with higher levels of T. Neuroprotective effects of T treatment were also assessed in quadriceps motoneurons in female rats (adult female rats lack the SNB neuromuscular system). As described above, motoneurons innervating the vastus medialis muscles were selectively killed by saporin injection, and females were given T implants (resulting in plasma levels of 2.0-2.5 ng/ml) or left untreated. Four weeks later, motoneurons innervating the ipsilateral vastus lateralis muscles were labeled with cholera toxin-conjugated HRP, and dendritic arbors were reconstructed. As in males, partial motoneuron depletion in females resulted in dendritic atrophy (52% of normal length) in remaining quadriceps motoneurons, and this atrophy was attenuated (70% of normal length) with T treatment. Together, these findings suggest that the neuroprotective effects of T on dendrites are achieved with dosages within the normal physiological range, and furthermore can be observed in motoneurons of both male and female rats.

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Ferguson AS, Sengelaub DR (2007) Dendritic atrophy following partial motoneuron depletion: time course of recovery and protection with testosterone. Neuroscience 2007 Abstracts 56.24/S18. Society for Neuroscience, San Diego, CA.

Summary: In male rats, motoneurons of the spinal nucleus of the bulbocavernosus (SNB) project to the bulbocavernosus and levator ani (BC/LA) muscles, and both the motoneurons and their target muscles are highly androgen-sensitive. We have previously demonstrated that partial depletion of motoneurons from the SNB induces dendritic atrophy in remaining motoneurons, and that treatment with testosterone (T) is neuroprotective against this atrophy. In the present study, we assessed dendritic atrophy after partial motoneuron depletion in SNB motoneurons at a variety of time points, to determine its time course and pattern with and without T treatment. Motoneurons innervating the BC/LA muscles in gonadally intact males were selectively killed by intramuscular injection of cholera toxin-conjugated saporin. Simultaneously, saporin-injected males were given T implants (45mm) or left untreated. At 2, 4, 6, or 10 weeks after motoneuron depletion, motoneurons innervating the contralateral BC were labeled with cholera toxin-conjugated HRP, and dendritic arbors were reconstructed in 3 dimensions. As previously reported, partial motoneuron depletion resulted in dendritic atrophy in remaining SNB motoneurons. While motoneuron depletion occurs within 7 days after saporin injection, dendritic atrophy in remaining SNB motoneurons progresses linearly over several weeks, with a decrease of 32% present at 2 weeks after motoneuron depletion, and a decrease to 66% at 4 weeks. Evidence of recovery in dendritic lengths was observed at 6 weeks post depletion (only 43% decreased), and by 10 weeks SNB dendritic lengths had returned to those of normal, intact males. Treatment with T altered the pattern of dendritic atrophy. While initial dendritic atrophy was similar to that of untreated saporin-injected males (29% decreased at 2 weeks post motoneuron depletion), T treatment attenuated dendritic atrophy. Four weeks after motoneuron depletion, SNB dendritic lengths had not declined further in T-treated males (32% decreased), and were now 102% longer than those of untreated, saporin-injected males. These findings suggest that SNB dendrites undergo a protracted atrophy and subsequent recovery following partial motoneuron depletion, and that the neuroprotective effects of T attenuate the magnitude of the induced atrophy.

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Cai L, Johnson DA (2007) Poster: Recognition of novel objects and their location in rats with selective cholinergic lesion of the medial septum. Neuroscience 2007 Abstracts 92.21/TT2. Society for Neuroscience, San Diego, CA.

Summary: The goal of this project was to determine whether cholinergic neurons projecting from the medial septum (MS) to the hippocampus play a role in novel object recognition or location. The specific aim was to determine whether lesion of cholinergic neurons in MS by the selective cholinergic neurotoxin 192IgG-saporin (SAP) would induce retrograde amnesia and/or anterograde amnesia for a novel object and/or its location. Male SD rats were tested in an object recognition paradigm. The time the rats spent examining old and novel objects was measured. Infusion of SAP into medial septum was performed 2 days after a one week pre-surgery training. Fourteen days after surgery post-surgery retention testing for retrograde object memory was carried out. Then 3 days later, a new acquisition training and retention testing for anterograde memory was started. One-way ANOVA and Fisher’s exact test were used for statistical analysis. There were no significant differences in the exploration ratios between the control group without surgery and the CSF surgical group. The mean exploration ratios for both groups demonstrated retention of memory for the novel object and its placement. SAP infusion into the MS failed to induce a deficit in retrograde amnesia 2 days after training, but did show a strong trend for anterograde amnesia for novel object recognition and a significant association with anterograde amnesia for object location. Conclusions were that cholinergic neurons of MS were not involved in retrograde object memory 2 days before the infusion of SAP and may or may not be necessary for anterograde object memory formation, but cholinergic neurons of the MS were involved in anterograde spatial memory formation for novel objects.

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Khan IM, Wart CV, Singletary EA, Stanislaus S, Deerinck T, Yaksh TL, Printz MP (2008) Elimination of rat spinal substance P receptor bearing neurons dissociates cardiovascular and nocifensive responses to nicotinic agonists. Neuropharmacology 54(2):269-279. doi: 10.1016/j.neuropharm.2007.09.014

Summary: Nocifensive behavior and cardiovascular responses due to nicotinic agonists may be sustained by substance P-positive primary afferents. Rats received 10-µl intrathecal injections of 10 µM SP-SAP (Cat. #IT-07); unconjugated saporin (Cat. #PR-01) was used as a control. Lesioned animals displayed reduced nocifensive response to nicotinic agonists. Tachycardia and pressor responses were enhanced upon administration of cytisine and epibatidine.

Related Products: Saporin (Cat. #PR-01), SP-SAP (Cat. #IT-07)

Percaccio CR, Pruette AL, Mistry ST, Chen YH, Kilgard MP (2007) Sensory experience determines enrichment-induced plasticity in rat auditory cortex. Brain Res 1174:76-91. doi: 10.1016/j.brainres.2007.07.062

Summary: Animals housed in enriched environments display numerous signs of good neural health. In this work the authors examined the role acetylcholine plays in this plasticity. 2.6 µg of 192-IgG-SAP (Cat. #IT-01) was injected into the left lateral ventricle of rats. Auditory evoked responses were used to assess the effect of lesioning cholinergic neurons. Response strength was not reduced in lesioned animals, indicating that cholinergic deficits do not affect this system.

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Caudle RM (2007) Featured Article: Inducing central sensitization with a substance P/ cholera toxin conjugate. Targeting Trends 8(4)

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Read the featured article in Targeting Trends.

See Also:

• Caudle RM Sensitization of spinal cord nociceptive neurons with a conjugate of substance P and cholera toxin. BMC Neuroscience 8:30, 2007.