Effect of muscle denervation on the expression of substance P in the ventral raphe-spinal pathway of the rat

Effect of Bladder Injection of OnabotulinumtoxinA on the Central Expression of Genes Associated with the Control of the Lower Urinary Tract: A Study in Normal Rats

To investigate a possible central mechanism of action of Botulinum toxin A (BoNT/A) following injection in the bladder, complementary to the acknowledged peripheral bladder effect, we studied changes in the expression of neuropeptides and receptors involved in lower urinary tract function in the spinal cord (SC) and dorsal root ganglia (DRG) of normal rats following BoNT/A bladder injection. Thirty-six Sprague-Dawley rats, divided into three groups of n = 12, received bladder injections of 2U or 5U OnabotulinumtoxinA (BOTOX^®), or saline. Six animals from each group were sacrificed on days 7 and 14. Expression of Tachykinin 1 (Tac1), capsaicin receptor (TRPV1), neuropeptide Y (NPY), proenkephalin (PENK) and muscarinic receptors M1, M2, M3, was evaluated in the bladder, L6-S1 DRG, and SC segments using real-time PCR and Western blotting. Real-time PCR revealed increased expression of NPY in all tissues except for SC, and increased TRPV1 and PENK expression in DRG and SC, whereas expression of Tac1, M1 and M2 was decreased. Less significant changes were noted in protein levels. These findings suggest that bladder injections of OnabotulinumtoxinA may be followed by changes in the expression of sensory, sympathetic and cholinergic bladder function regulators at the DRG/SC level.

Botulinum toxin type A in chronic migraine

The use of botulinum toxin type A continues to be investigated by the US FDA for potential use in the treatment of headache. As part of this process there has been extensive research conducted by individual study sites as well as multicenter trials. To date, the majority of the focus has been on migraine headache as well as on tension-type headache. The results of these studies have been mixed. A variety of issues may contribute to the mixed results, including difference in the dose of toxin used, the number of injection sites utilized, the treatment paradigm itself, confounding medications, high and prolonged placebo response, as well as patient selection issues. Currently, the focus on botulinum toxin type A is on those patients who have chronic daily headache with a migraine component to their clinical picture. The results of two large trials in this population produced positive findings, especially when consideration is given to the a priori additional analyses of this complex patient population. The results of these studies have allowed a more focused program to be undertaken in the Phase III evaluation. At the same time, additional work has been performed to understand the mechanism by which botulinum toxin type A may work to alleviate migraine. This work may contribute substantially to improving outcomes with botulinum toxin type A. Characterization of the mechanism of action in pain may be crucial to outcomes because many issues are related to central sensitization.

Injections of botulinum toxin type a produce pain alleviation in intractable trigeminal neuralgia

To report the effects of local injections of botulinum toxin type A regarding pain relief and long-term control in a patient with intractable trigeminal neuralgia. The patient was a 75-year-old man with trigeminal neuralgia in the left hemifacial region. His pain was unbearable and could not be controlled by carbamazepine, amitriptyline, or blocked by infiltration of a glycerol solution or phenol. The authors evaluated pain intensity, quality, and location using a Visual Analog Scale to establish the efficacy of botulinum toxin type A injections. Two units of botulinum toxin type A (Botox) were subcutaneously injected once in eight points distributed along the territory of V1 and V2. Visual Analog Scores were measured at baseline and at 7, 30, 60, and 90 days after treatment. The authors also examined the patient's general condition and daily life activities. The Visual Analog values were, respectively, 82, 54, 25, 25, and 45 mm at each follow-up examination. No side effects were observed on the site of injection and on the patient's clinical state. The authors have been able to reduce trigeminal neuralgia pain with botulinum toxin type A injections in the V1, V2 territory during all the period of study, as well as to withdraw all medication. Interestingly, there was concomitant reduction of pain also in V3, which was not injected.

Preventative treatment for migraine and tension-type headaches : do drugs having effects on muscle spasm and tone have a role?

Baclofen, tizanidine and botulinum toxin A, agents used to treat disorders of muscle tone, have been studied as potential preventative treatments for migraine, tension-type headache and other related disorders. The most extensive work has been completed with botulinum toxin A. However, there is still a paucity of well controlled, clinical trials with this agent, and overall there have been conflicting and oftentimes equivocal results: studies of its use in migraine headache have suggested efficacy, whereas those of tension-type headache have not shown significant evidence of efficacy. There were few significant adverse events associated with the use of botulinum toxin A in these trials. The mechanism by which botulinum toxin A may work to prevent headache is not clear. Although changes in muscle tone may play a role in the effect of the drug, central mechanisms such as effects on neuropeptides involved in the pathogenesis of migraine may also be relevant. Further clinical trial work is in progress to help determine optimal administration schedules and choice of injection locations with botulinum toxin A for specific headache disorders. There has been limited study of the use of baclofen, an agent that acts centrally via GABA(A) receptors, in migraine and cluster headache, with only two open trials conducted to date. Both of these studies support the use of baclofen in the preventive treatment of headache.Tizanidine, which may have both a peripheral and a central mechanism in the locus ceruleus in migraine headache, has been studied in several clinical trials. Although the primary mechanism of action of this agent is, like clonidine, as an alpha-adrenoceptor agonist, it has little antihypertensive effect. Open trials of tizanidine have shown it to be useful in chronic headache. One well controlled trial, conducted as a follow-up to an open-label trial in the preventive treatment of chronic daily headache, reported tizanidine as having a statistically significant benefit over placebo. Also of interest is its use in conjunction with a long-acting NSAID to aid in the treatment of rebound headache accompanying the discontinuation of overused acute migraine therapies. In conclusion, though limited, the studies suggest the efficacy of botulinum toxin A, baclofen and tizanidine in primary headache disorders.

[Botulinum toxin in headache]

Use of botulinum toxin in headache is a recent method. More and more studies are dedicated to this method. However, despite the large number of published studies, results are contradictory. It is actually difficult to conclude that this therapy is effective or not due to the disparity of clinical studies. Nevertheless, some results are encouraging and studies with a large number of patients have to be done. Here, we take stock about pathophysiological data on the effect of botulinum toxin on pain. Then, we'll report a review of clinical studies available on literature.

Differential susceptibility to ageing of rat preganglionic neurones projecting to the major pelvic ganglion and of their afferent inputs

We have analysed age-related changes in the morphology of preganglionic neurones in the lumbosacral spinal cord, labelled following injection of retrograde tracers into the major pelvic ganglion of young adult and aged male rats. We have also examined changes in neurotransmitter-characterised spinal afferent inputs to these neurones, or to the nuclei in which they lie, using light and electron microscope immunohistochemistry. In previous investigations of the major pelvic ganglion, the sympathetic, but not parasympathetic, postganglionic neurones were seen to exhibit age-related changes and the same pattern is seen in the preganglionic neurones. This included an apparent reduction in the numbers of sympathetic preganglionic neurones, and a reduction in the length of their dendrites and the complexity of their branches. Ultrastructural immunohistochemical studies described here reveal significant reductions in the area of synaptic contact made by glutamate-immunoreactive boutons onto the dendrites of sympathetic (but not parasympathetic) preganglionic neurones, while contacts from boutons immunoreactive for glycine or gamma-aminobutyric acid (GABA) were unchanged. There is also a reduction in synaptic contacts received by sympathetic somata from boutons immunoreactive for none of these amino acids. Serotonin-immunoreactive terminals are closely associated with preganglionic autonomic neurones, and these are reduced in number in sympathetic, but not parasympathetic, spinal nuclei of aged rats. However, serial section electron microscopy has so far failed to demonstrate conventional synaptic contacts between serotonergic terminals and the dendrites or somata of the preganglionic autonomic neurones. In young animals, axon terminals immunoreactive for thyrotropin-releasing hormone (TRH) are abundant in all spinal laminae including area X, but in aged animals, such terminals are significantly reduced in number in regions containing preganglionic sympathetic, but not parasympathetic, neurones. These results indicate that the sympathetic preganglionic neuron populations that project to the major pelvic ganglion, and the spinal inputs they receive, show a number of degenerative changes in aged rats which are not seen parasympathetic preganglionic neuronal populations.

Enkephalin and aFGF are differentially regulated in rat spinal motoneurons after chemodenervation with botulinum toxin

Botulinum toxin is used to induce transient graded paresis by chemodenervation in the treatment of focal hyperkinetic movement disorders. While the molecular events occurring in motoneurons after mechanical nerve lesioning leading to muscle paresis are well known, they have been investigated to a lesser extent after chemodenervation. We therefore examined the expression of enkephalin (ENK), acidic fibroblast growth factor (aFGF), neurotensin (NT), galanin (GAL), substance P (SP), vasoactive intestinal polypeptide (VIP), and neuropeptide Y (NPY) in rat spinal motoneurons after chemodenervation of the gastrocnemius. In order to precisely localize the motoneurons targeting the injection site, retrograde tracing was performed in additional rats by using Fluorogold injections. ENK expression was upregulated in the region corresponding to the Fluorogold positive motoneurons, but also on the contralateral side and in more distant parts of the spinal cord. The highest upregulation occurred 7 to 14 days after injections and decreased over a period of three months. At 8 days, aFGF was slightly downregulated in all regions studied, single motoneurons showed NT expression, while expression of GAL, SP, VIP, and NPY could be detected neither in controls nor in toxin-treated animals. These alterations in gene expression were strikingly different from those described after axotomy. Our present findings give additional demonstration of the considerable plasticity of the adult spinal cord after botulinum toxin treatment.

Pharmacologic characterization of botulinum toxin for basic science and medicine

The use of Botulinum neurotoxin (BoNT) is increasing in both clinical and basic science. Clinically, intramuscular injection of nanogram quantities of BoNT is fast becoming the treatment of choice for a spectrum of disorders including movement disorders such as torticollis, blepharospasm, Meige Disease, and hemifacial spasm (Borodic et al., 1991, 1994a; Jankovic and Brin, 1991; Clarke, 1992). Neuroscientists are using BoNTs as tools to develop a better understanding of the mechanisms underlying the neurotransmitter release process. Consequently, our ability to accurately and reliably quantify the biologic activity of botulinum toxin has become more important than ever. The accurate measurement of the pharmacologic activity of BoNTs has become somewhat problematic with the most significant problems occurring with the clinical use of the toxins. The biologic activity of BoNTs has been measured using a variety of techniques including assessment of whole animal responses to in vitro effects on neurotransmitter release. The purpose of this review is to examine the approaches employed to characterize, quantify and investigate the actions of the BoNTs and to provide a guide to aid investigators in determining which of these methods is most appropriate for their particular application or use.