Inhibitory effects of botulinum toxin on 5-HT1C receptor-induced Cl- current in Xenopus oocytes

Effects of botulinum toxin type A facial injection on monoamines and their metabolites in sensory, limbic and motor brain regions in rats

Despite its toxicity, botulinum neurotoxin type A (BTX-A) is a valuable therapeutic agent for several motor, autonomic and pain disorders. Numerous studies have described its peripheral as well as central effects. Using reversed-phase High Performance Liquid Chromatography with Electrochemical Detection (HPLC-ED) and gradient elution, we quantified the concentrations of dopamine (DA), noradrenaline (NA), serotonin (5-HT) and their metabolites in 10 brain regions, ipsilateral and contralateral from the site of unilateral BTX-A administration (5 U/kg) into the rat whisker pad. In regions associated with nociception and pain processing we also examined possible BTX-A effects in combination with formalin-induced inflammatory orofacial pain. The dominant BTX-A effects on the monoamines and their metabolites were insignificant. The only significant increase caused by BTX-A alone was that of NA in striatum and serotonin in hypothalamus. While antinociceptive effects of BTX-A are most probably not related to central monoamine concentrations, the localized increased NA and 5-HT concentrations might play a role in reported BTX-A efficacy for the treatment of depression.

[Cellular and molecular pharmacological studies on membrane receptor-signaling and stress-responses in the brain]

Studies on the cellular and molecular mechanism of neurotransmitter receptor-signaling and of neuronal and glial cell responses to stresses seem to be important to elucidate the action mechanism of centrally-acting drugs and to develop novel therapeutics against several diseases in the brain. The present review shows our findings with regard to the membrane receptor-signaling mechanism including serotonin, noradrenaline, glutamate receptors, ion channels, G-proteins, protein kinases and drug actions in Xenopus oocytes injected with rat brain mRNA, NG108-15 cells and brain membranes. Regarding the results of studies on the inter- and intra-cellular mechanism of neurons and glial cells against cerebral ischemia/hypoxia, we review the involvement of a transcription factor NF-kappa B in LPS-elicited inducible NO synthase (iNOS) expression in rat astroglial cells. Then we describe possible involvement of: 1) ADP-ribosylation/nitrosylation of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and 2) decrease in mitochondrial membrane potential, release of caspase-3 from mitochondria and degradation of the inhibitor of caspase-activated DNase by activated caspase in NO-induced neuronal apoptosis. We observed that hypoxia results in expression of a molecular chaperon such as protein disulfide isomerase (PDI) and HSP70 in astroglial cells. Our recent findings indicate that overexpression of PDI in the rat hippocampus (in vivo) and in neuroblastoma SK-N-MC cells (in vitro) significantly suppress the hypoxia-induced neuronal death. From physiological/pathophysiological and pharmacological aspects, we review the importance of studies on the cellular and molecular mechanism of membrane receptor-signaling and of stress-responses in the brain to identify functional roles of neuro-glial- as well as neuro-neuronal interaction in the brain.

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.

Possible involvement of botulinum ADP-ribosyltransferase sensitive low molecular G-protein on 5-hydroxytryptamine (5-HT)-induced inositol phosphates formation in 5-HT2c cDNA transfected cells

To clarify the involvement of botulinum ADP-ribosyltransferase sensitive low molecular G-proteins in 5-hydroxytryptamine (5-HT)-induced stimulation of phosphatidylinositol turnover, we examined the effects of 5-HT on inositol phosphates formation in COS 7 cells transfected with 5-HT2c receptor cDNA, but did not in non-transfected or vector-transfected cells. A typical 5-HT2c receptor antagonist mianserin (0.3-3 microM) inhibited the 5-HT-induced inositol phosphates formation. Treatment with botulinum toxin D preparation (20 micrograms/ml, 8 h) that contained botulinum C3 ADP-ribosyltransferase, blocked the 5-HT-induced inositol phosphate formation, although botulinum toxin A preparation that did not contain the enzyme did not have an influence. These results support our previous findings suggesting that low molecular weight G-proteins ADP-ribosylated by botulinum ADP-ribosyltransferase are involved in phospholipase C activity.