Pharmacological analysis of Poecilotheria spider venoms in mice provides clues for human treatment.

Bites of tiger spiders belonging to Poecilotheria genus cause moderate to severe pain and long-lasting local or generalized muscle cramps in humans. Bites occur in regions of the spiders' natural habitat, India and Sri Lanka, but the popularity of these colorful tarantulas as pets leads to reports of envenomation cases worldwide. Treatment is predominantly symptomatic and often inadequate since there is almost no clinical or toxicology research data available, and physicians outside India or Sri Lanka typically have no experience in treating such cases. We report toxicity studies of venom from nine Poecilotheria species in laboratory mice (Mus musculus Balb/C males). LD50 values are 5-14 mg of lyophilized crude venom per 1 kg (i.v.). The major symptoms of envenomation include tonic-clonic seizures, jerks, characteristic motor stereotypy, and hyperalgesia and point to voltage-gated sodium channels as a potential target of the venom components. Poecilotheria fasciata venom effects were studied in detail at a sub-lethal dose of 5 mg/kg (LD50 = 12 mg/kg). 13 widely used pharmacological agents (atropine, chloropyramine, chlorpromazine, diazepam, ethanol, flupirtine, haloperidol, ketotifen, lamotrigine, oxcarbazepine, tolperisone, xylazine, and CaCl2) were checked for ability to suppress the envenomation symptoms. Chlorpromazine (10 mg/kg, i.p.), oxcarbazepine (60 mg/kg, p.o.), tolperisone (50 mg/kg, s.c.) and xylazine (2.5 mg/kg, i.p.) were found effective as a pretreatment to mitigate muscle cramps and motor stereotypy. When administered after envenomation chlorpromazine (5 mg/kg, i.v.) effectively reduced the cramps, while oxcarbazepine (30 mg/kg, i.v.) and xylazine (1 mg/kg, i.v.) suppressed the stereotypy.

Prenatal lipopolysaccharide induces hypothalamic dopaminergic hypoactivity and autistic-like behaviors: Repetitive self-grooming and stereotypies.

Previous investigations by our group have shown that prenatal exposure to lipopolysaccharide (LPS), which mimics infection by gram-negative bacteria, induces social, cognitive, and communication deficits. For a complete screening of autistic-like behaviors, the objective of this study was to evaluate if our rat model also induces restricted and repetitive stereotyped behaviors. Thus, we studied the self-grooming microstructure. We also studied the neurochemistry of hypothalamus and frontal cortex, which are brain areas related to autism to better understand central mechanisms involved in our model. Prenatal LPS exposure on gestational day 9.5 increased the head washing episodes (frequency and time), as well as the total self-grooming. However, body grooming, paw/leg licking, tail/genital grooming, and circling behavior/tail chasing did not vary significantly among the groups. Moreover, prenatal LPS induced dopaminergic hypoactivity (HVA metabolite and turnover) in the hypothalamus. Therefore, our rat model induced restricted and repetitive stereotyped behaviors and the other main symptoms of autism experimentally studied in rodent models and also found in patients. The hypothalamic dopaminergic impairments seem to be associated with the autistic-like behaviors.

Loss of glutamatergic pyramidal neurons in frontal and temporal cortex resulting from attenuation of FGFR1 signaling is associated with spontaneous hyperactivity in mice.

Fibroblast growth factor receptor (FGFR) gene products (Fgfr1, Fgfr2, Fgfr3) are widely expressed by embryonic neural progenitor cells throughout the CNS, yet their functional role in cerebral cortical development is still unclear. To understand whether the FGF pathways play a role in cortical development, we attenuated FGFR signaling by expressing a tyrosine kinase domain-deficient Fgfr1 (tFgfr1) gene construct during embryonic brain development. Mice carrying the tFgfr1 transgene under the control of the Otx1 gene promoter have decreased thickness of the cerebral cortex in frontal and temporal areas because of decreased number of pyramidal neurons and disorganization of pyramidal cell dendritic architecture. These alterations may be, in part, attributable to decreased genesis of T-Brain-1-positive early glutamatergic neurons and, in part, to a failure to maintain radial glia fibers in medial prefrontal and temporal areas of the cortical plate. No changes were detected in cortical GABAergic interneurons, including Cajal-Retzius cells or in the basal ganglia. Behaviorally, tFgfr1 transgenic mice displayed spontaneous and persistent locomotor hyperactivity that apparently was not attributable to alterations in subcortical monoaminergic systems, because transgenic animals responded to both amphetamine and guanfacine, an alpha2A adrenergic receptor agonist. We conclude that FGF tyrosine kinase signaling may be required for the genesis and growth of pyramidal neurons in frontal and temporal cortical areas, and that alterations in cortical development attributable to disrupted FGF signaling are critical for the inhibitory regulation of motor behavior.