targeted-toxins

Kaushal R, Ma F, Zhang L, Bright CR, Taylor BK, Westlund KN (2012) Knockdown of noradrenergic locus coeruleus (LC) neurons alleviates chronic orofacial pain. Neuroscience 2012 Abstracts 164.19. Society for Neuroscience, New Orleans, LA.

Summary: Trigeminal neuralgia (TN) is an excruciating and debilitating form of clinical orofacial pain. Noradrenergic locus coeruleus (LC, pontine A6 neurons) is involved in bidirectional modulation of pain. Multiple studies indicate that LC activity is increased during noxious stimulation and following inflammation or nerve damage. Predominantly known for its role in the feedback inhibition of pain, emerging studies also indicate a contribution of the LC in pain facilitation. For example, lesions of the LC significantly reduce tonic behavioral responses to intraplantar formalin injection, prevent autotomy, and reduce hypersensitivity associated with peripheral nerve injury. In this study we hypothesized that noradrenergic (LC) neurons contribute to the facilitation of chronic pain in TN. We used a rat model of TN involving infraorbital nerve chronic constriction injury (ION-CCI) which produces mechanical hypersensitivity as assessed by a reduction in von Frey threshold. Administration of anti-dopamine-β-hydroxylase saporin (anti-DβH-saporin) toxin was performed for selective elimination of noradrenergic LC neurons or IgG saporin (nonspecific) as the control either by intracerebroventricular (i.c.v space 2) or by bilateral spinal trigeminal nucleus (STN) injections. Under minimal restraint, rats received either no stimulation or repeated stimulation with either a 2 or 15-gm von Frey hair applied directly to the maxillary branch. Withdrawal threshold (tactile allodynia) from von Frey fiber stimulation to the face was not changed as compared to baseline in animals subjected to sham surgery; this was true in both saporin and anti-DβH-saporin groups. However, i.c.v. anti-DβH-saporin significantly increased withdrawal threshold animals with ION-CCI as compared to IgG saporin controls. More selective destruction of the LC-trigeminal pathway with bilateral STN anti-DβH-saporin injection also alleviated behavioral signs of chronic orofacial hyperalgesia. Elimination of noradrenergic LC neurons was confirmed by complete loss of tyrosine hydroxylase (TH) immunoreactivity in anti-DβH-saporin injected animals. Compared to unstimulated controls, mechanical stimulation increased immunoreactive phosphorylated extracellular cell-regulated protein kinase (pERK), a marker of neuronal activity, in the LC and STN. Nerve injury also increased expression of a neuronal injury and stress marker, activating transcription factor 3 (ATF3), in trigeminal ganglia neurons. Together, these results indicate that noradrenergic locus coeruleus neurons facilitate chronic orofacial neuropathic pain.

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

Mathis C, Moreau P-H, Zerbinatti C, Goutagny R, Cosquer B, Geiger K, Kelche C, Cassel J-C (2012) Combined loss of entorhinal and basal forebrain cholinergic hippocampal inputs deeply impairs spatial navigation memory in C57BL/6J and hAPPxapoE mice. Neuroscience 2012 Abstracts 203.28. Society for Neuroscience, New Orleans, LA.

Summary: The hippocampus plays a key role in spatial learning and memory. Major inputs provided by the cholinergic basal forebrain (CBF) and the entorhinal cortex (EC) neurons are expected to modulate hippocampal functions. Surprisingly, the selective lesion of one or the other produces only moderate performance degradation in spatial navigation tasks, suggesting possible compensation provided by other hippocampal inputs. We therefore assessed the effects of single versus combined lesions of the EC (NMDA excitotoxin) and the CBF (mu-p75 saporin immunotoxin) on several forms of memory in C57BL/6 mice. Single lesions had moderate or no effects, while the combined lesions completely abolished long-term spatial memory retention in the water-maze and the Barnes-maze navigation tasks. Object recognition memory was selectively and profoundly affected by the loss of cholinergic neurons, whereas object location memory was only marginally affected by the lesions. These results suggest that the integrity of both the CBF and the EC is critical to establish an enduring spatial navigation memory. The synergistic interaction between the two lesions is particularly relevant to Alzheimer’s disease (AD) since both structures undergo severe degeneration in parallel to dramatic impairments in spatial navigation tasks. The apolipoprotein E4 (apoE4) allele, a major genetic risk factor for AD, has been proposed as a cholinergic deficit predictor and has been associated with larger EC atrophy in AD patients. Thus, the effects of single and combined EC and CBF lesions were evaluated on Barnes maze navigation performance in hAPPxapoE mice knocked-in for the human apoE3 or apoE4 gene allele on a (normal) human APP YAC transgenic background. Long-term spatial memory performances of hAPPxapoE3 and hAPPxapoE4 mice were dramatically affected by the CBF lesion and the combined lesions, but not by the EC lesion. A similar pattern of deficit was observed on learning performances in apoE4 not in apoE3 mice; the latter were only affected by the combined lesions. In conclusion, the apoE4 genotype had no effect on the consequences of EC and combined lesions, but it worsened the outcome of CBF lesions compared to the apoE3 genotype. Since the mice of the two genotypes showed similar loss of cholinergic neurons, our data may reflect a deleterious impact of apoE4 on the activity of the few surviving neurons (about 20%). Alternatively, our findings would also be consistent with impaired compensatory mechanisms following cholinergic loss which could depend on other hippocampal inputs such as the entorhinal cortex. Further analyses are underway to clarify this issue.

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

Hayward LF (2012) Neurotoxic lesion of CRF-R1 neurons in the amygdala selectively attenuates the heart rate response to acute stress in the spontaneously hypertensive rat. Neuroscience 2012 Abstracts 281.28. Society for Neuroscience, New Orleans, LA.

Summary: The magnitude of a person’s autonomic response to mental stress is predictive of one’s risk for the development of cardiovascular disease and has been linked to indicators of exaggerated neuronal activity in the amygdala. Recent evidence from our lab identified a link between changes in the expression of the neuropeptide corticotrophin-releasing factor (CRF) within the central nucleus of the amygdala (CEA) to exaggerated cardiovascular responses to acute stress in the spontaneously hypertensive rat (SHR). The present study was undertaken to evaluate the impact of selective lesion of CRF-R1 neurons in the amygdala on the cardiovascular response to acute air jet stress (AJS) in the SHR. Male SHR rats underwent local bilateral microinjections of 10 nanograms/200 nl per side of blank-saporin (n=4) or CRF-receptor (R1) targeting saporin (n=4) into the region of the CEA. Following 7-10 days of recovery and two days following arterial catheter instrumentation, animals underwent AJS testing. CRH-R1 lesion in the amygdala produced a small reduction in resting systolic blood pressure (160±6 vs 173±4 mmHg, p<0.1) but not change in heart rate (354±16 vs 352±+4 bpm). CRH-R1 lesion also significantly attenuated the mean rise heart rate in response to AJS (72±21 vs 130±13 bpm) and facilitated a more rapid heart rate recovery independent of any effect on the blood pressure response to AJS. The findings demonstrate for the first time that CRF-R1 activation in the amygdala selectively contributes to the elevated heart rate response to stress in individuals with hypertension, thus providing a link between the exaggerated activity in the amygdala and a specific cardiovascular response to stress.

Related Products: CRF-SAP (Cat. #IT-13)

Ye Y, Viet CT, Dang D, Schmidt BL (2012) IB4 (+) neurons contribute to force-induced cancer pain but not cancer proliferation. Neuroscience 2012 Abstracts 67.10. Society for Neuroscience, New Orleans, LA.

Summary: The primary treatment for cancer pain is μ-opiates; however, often μ-opiates are not effective and they produce multiple debilitating side effects. Recent studies show that μ- and δ-opioid receptors are separately expressed on IB4 (-) and IB4 (+) neurons, which mediate thermal and mechanical pain, respectively. We investigated the contribution of IB4 (+) and IB4 (-) neurons to cancer-induced mechanical and thermal hypersensitivity and investigated the role of these fibers to cancer proliferation. We used two separate mouse cancer pain models: 1) a cancer supernatant injection model, and 2) an orthotopic cancer model. The former model isolated the effect of the cancer secretome while the latter examined the effect of the following constituents within the cancer microenvironment: the cancer, the cancer secretome and the host tissue. Using the cancer supernatant model, along with injection of a selective δ-opioid receptor agonist and a P2X3 antagonist to target IB4 (+) neurons, we showed that IB4 (+) neurons played arole in cancer-supernatant-induced mechanical allodynia, but not thermal hyperalgesia. Selective ablation of IB4 (+) neurons in the spinal cord using IB4-saporin affected cancer-supernatant-induced mechanical but not thermal hypersensitivity. In the orthotopic cancer model, mice with paw cancer exhibited both mechanical and thermal hypersensitivity. Selective ablation of IB4(+) neurons decreased mechanical hypersensitivity; however thermal hypersensitivity was increased. We hypothesized that increased thermal hyperalgesia was associated with a compensatory elevation of TRPV1 expression in the spinal cord. Thermal latency in the mouse cancer paw was increased by intrathecal TRPV1 antagonist and selective removal of TRPV1 terminals by capsaicin in the IB4-saporin treated mice compared to saporin treated mice. Mechanical threshold was not affected by either the TRPV1 antagonist or capsaicin treatment. In the spinal cord, TRPV1 protein levels were increased in cancer mice compared to naïve mice, and TRPV1 was likely to be increased in the IB4-saporin treated cancer mice compared to saporin treated cancer mice. We investigated cancer proliferation by measuring tumor volume. Tumor volume was not affected by selective ablation of IB4 (+) neurons. Our findings suggest that peripherally administered pharmacological agents targeting IB4 (+) neurons, such as a selective δ-opioid receptor agonist or P2X3 antagonist, might be effective for treating cancer pain in patients. Acknowledgements: Supported by NIH/NIDCR R21 DE018561

Related Products: IB4-SAP (Cat. #IT-10)

Jokiaho A, Donovan C, Watts A (2012) Catecholaminergic neurons in the ventrolateral medulla are differentially activated by the rate of fall in blood glucose during hypoglycemia, and are required for the rate-dependent hypoglycemic activation of sympathoadrenal responses. Neuroscience 2012 Abstracts 93.05. Society for Neuroscience, New Orleans, LA.

Summary: Hypoglycemic counterregulation is mediated by glucosensors located in the hypothalamus, hindbrain, and portal-mesenteric veins (PV). We have previously shown that when hypoglycemia develops slowly PV glucose sensing is critical for both the sympathoadrenal response and hindbrain Fos activation. Hindbrain catecholaminergic (CA) neurons provide extensive inputs to the hypothalamus and are key participants in the control of energy homeostasis and in the responses to glycemic challenges. However, the role of the various CA cell groups together with the organization of the circuitry between peripheral and central glucose sensing units and the effectors that mediate counterregulatory response to hypoglycemia are unknown. To investigate the role of CA neurons in this network we use hyperinsulinemic-hypoglycemic clamps to induce fast (20mins)- or slow (75min)-onset hypoglycemia in male Wistar rats with saporin/anti-dopamine β-hydroxylase (DBH) DSAP immunotoxin lesions. The hypothalamic paraventricular nucleus (PVH) was injected bilaterally with DSAP or saporin conjugated to mouse IgG (SAP) as controls. PVH DSAP lesions remove about 80% of the DBH-ir and PNMT-ir cell bodies in the ventrolateral medulla. We found that hypothalamic CA afferents are required for sympathoadrenal (epinephrine and nor-epinephrine) responses to slow- but not fast-onset hypoglycemia. We also found robust Fos activation in CA neurons in the ventrolateral (A1, C1) and the dorsomedial medulla, particularly in the nucleus of the solitary tract (NTS; A2, C2). In rats with intact forebrain CA innervations, fast-onset hypoglycemia led to significantly greater DBH/Fos colocalization in the A1, A1/C1 and C1 regions compared to slow-onset hypoglycemia. We further identified substantial numbers of Fos-positive nuclei colocalized in adrenergic neurons (phenylethanolamine-N-methyltransferase (PNMT)) in the A1/C1 and C1 regions, and again these numbers were greater in fast-onset compared to slow-onset hypoglycemia. In SAP and DSAP animals, slow- and fast -onset hypoglycemia led to robust Fos expression in the area postrema and medial parts of the NTS. However, in these two regions there was virtually no Fos and DBH/PNMT-ir colocalization showing that AP and NTS neurons activated following hypoglycemia are not CA. The mechanisms that process the sensory information responsible for sympathoadrenal counterregulatory responses to fast- and slow-onset hypoglycemia are clearly different. We now show that different rates of hypoglycemia onset engage distinct CA cell groups, which in turn differentially participate in rate-dependent counterregulatory responses.

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

Li A-J, Wang Q, Smith BR, Ritter S (2012) Lateral and fourth ventricular phloridzin injections stimulate feeding but do not produce hyperglycemia. Neuroscience 2012 Abstracts 93.18. Society for Neuroscience, New Orleans, LA.

Summary: Sodium-coupled glucose transporters (SGLTs) are a family of glucose transporter found in small intestine, kidney, brain capillaries and some neurons. Because SGLTs are membrane receptors, they interact with extracellular glucose in a metabolism-independent manner. Early work using the SGLT inhibitor, phlorizin, suggested that fourth ventricular phlorizin injection increased feeding, but not blood glucose (Flynn FW and Grill HJ, 1985). To further examine this finding, we injected phloridzin, a competitive inhibitor for SGLT-1 and SGLT-2 into the lateral ventricle (LV) or the 4th ventricle (4V) in rats, and the effects of the injections on food intake and blood glucose were examined. We found that both LV and 4V injections of phloridzin enhanced food intake in rats and that LV and 4V injections were of similar potency. In contrast, neither injection elevated blood glucose levels in the present experiments. We also found that enhancement of feeding by 4V phloridzin was abolished by medial hypothalamic injections of anti-dopamine beta hydroxylase saporin, a retrogradely transported catecholamine immunotoxin that selectively lesions norepinephrine and epinephrine neurons that innervate the injection site. Taken together, these results suggest that SGLT receptors in the brain constitute a novel, nonmetabolic, glucose sensing mechanism that contribute to control of food intake.

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

Cunningham C (2012) Featured Article: Partial basal forebrain cholinergic depletion leaves working memory susceptible to the effects of systemic inflammation. Targeting Trends 13(4)

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

Read the featured article in Targeting Trends.

See Also:

• Field RH et al. Prior pathology in the Basal forebrain cholinergic system predisposes to inflammation-induced working memory deficits: reconciling inflammatory and cholinergic hypotheses of delirium. J Neurosci 32(18):6288-6294, 2012.

Croxson PL, Browning PG, Gaffan D, Baxter MG (2012) Acetylcholine facilitates recovery of episodic memory after brain damage. J Neurosci 32(40):13787-13795. doi: 10.1523/JNEUROSCI.2947-12.2012

Summary: Episodic memory is controlled by several interconnected brain structures. The order in which these structures sustain damage can affect the processes lost. In this work the authors performed numerous bilateral injections of ME20.4-SAP (Cat. #IT-15) into the infero-temporal cortex, the medial surface of the temporal lobe, the perirhinal and entorhinal cortex, and the temporal pole of monkeys. These injections totaled 2.2-2.5 μg of conjugate. The results indicate that loss of cortical acetylcholine function will interfere with adaptation to memory impairments caused by structural damage in episodic memory centers.

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

Daubert DL, McCowan M, Erdos B, Scheuer DA (2012) Nucleus of the solitary tract catecholaminergic neurons modulate the cardiovascular response to psychological stress in rats. J Physiol 590(Pt 19):4881-4895. doi: 10.1113/jphysiol.2012.232314

Summary: It has been proposed that the nucleus of the solitary tract (NTS) is highly involved in cardiovascular regulation. In light of the fact that catecholaminergic neurons in the NTS are part of stress-related neurocircuitry, the authors investigated whether these neurons attenuate blood pressure increases due to stress. Rats received 22 ng bilateral injections of anti-DBH-SAP (Cat. #IT-03) into the NTS. Mean arterial pressure and baseline plasma epinephrine were measured in a restraint test. Animals lesioned with anti-DBH-SAP displayed a significantly enhanced mean arterial pressure, and reduced plasma epinephrine. These data suggest that catecholaminergic neurons in the NTS inhibit the arterial pressure response to stress, but maintain the corticosteroid response.

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

Babalola PA, Fitz NF, Gibbs RB, Flaherty PT, Li PK, Johnson DA (2012) The effect of the steroid sulfatase inhibitor (p-O-sulfamoyl)-tetradecanoyl tyramine (DU-14) on learning and memory in rats with selective lesion of septal-hippocampal cholinergic tract. Neurobiol Learn Mem 98(3):303-310. doi: 10.1016/j.nlm.2012.09.003

Summary: Steroid sulfatase inhibitors such as dehydroepiandrosterone (DHEAS) have memory-enhancing effects. Working with both DHEAS and the steroid sulfatase inhibitor DU-14, the authors examined cholinergic function by infusing 0.2 μg of 192-IgG-SAP (Cat. #IT-01) into the medial septum of rats. The results indicate that memory associated with contextual fear is facilitated by steroid sulfatase inhibition, but acquisition of spatial memory is impaired by these same lesions.

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