Adenylyl cyclases types 1 and 8 promote pro-survival pathways after ethanol exposure in the neonatal brain

Although a wide range of developmental disabilities following fetal alcohol exposure are observed clinically, the molecular factors that determine the severity of these sequelae remain undefined. In mice exposed to ethanol, deletion of adenylyl cyclases (ACs) 1 and 8 exacerbates the neuroapoptosis that occurs in a prolonged post-treatment period; however, it remains unclear whether AC1 and AC8 are critical to the primary or secondary mechanisms underlying ethanol-induced neurodegeneration. Here we demonstrate that mice lacking AC1 and AC8 (DKO) display significantly increased apoptosis in the striatum, a region sensitive to neuroapoptosis in the acute post-treatment period, compared to WT controls. The enhanced neuroapoptotic response observed in the striatum of DKO mice is accompanied by significant reductions in phosphorylation of known pro-survival proteins, insulin receptor substrate-1 (IRS-1), Akt and extracellular signal-regulated kinases (ERKs). These data suggest that AC1/AC8 are crucial activators of cell survival signaling pathways acutely following ethanol exposure and represent molecular factors that may directly modulate the severity of symptoms associated with Fetal Alcohol Syndrome

Dha抑制老鼠大腦海馬神經傳導與癲癇發作之研究

Docosahexaenoic acid (DHA) has been suggested to be required for neuronal development and synaptic plasticity. However, in view of the fact that DHA facilitates NMDA responses and blocks K+ channels, it might predispose the neurons to epileptiform bursting. By using extracellular recording of population spikes in the CA1 region of rat hippocampal slices, we tested this possibility by examining the effect of DHA on the epileptiform activity induced by bicuculline or in Mg2+-free medium. When stimuli were delivered to the Schaffer collateral/commissural pathway every 20 or 30 sec, DHA had no significant effect on the epileptiform activity. However, when the frequency of stimulation was increased to 0.2 Hz, DHA attenuated the amplitude of the bursting activity induced by bicuculline to 57.5 ?10. 8% and those induced by Mg2+-free ACSF to 65.8 ?13.9% of control. DHA reduced the slope of field excitatory postsynaptic potential (fEPSP) to 77 .1 ?7.4% of baseline, without significant effect on the ratio of paired- pulse facilitation (PPF). By intracellular recording of neurons in the stratum pyramidale of rat hippocampal slices, we found that DHA markedly inhibited the repetitive firing of action potentials elicited by depolarizing current pulses but did not affect the initial action potential. Thus, DHA may attenuate epileptic activity mainly through the frequency-dependent blockade of Na+ channels

Immunocytochemical Studies on Desmin and Vimentin in Neruomuscular Disorders

　　Desmin and vimentin are two intermediate filaments, abundant in fetal skeletal nuscle, ahnost undetectable in mature skeletal muscle which increase in regenerating and partially damaged skeletal muscle fibers. To determine their content in neuromuscular disorders immunohistochemical studies of desmin and vimentin were performed on 53 human nuscle specimens . The labelled streptavidin biotin technique (DAKO, LSAB Kit, alkaline phosphatase) was used. Strong staining intensity was seen in regenerating and partially damaged fibers of inflammatory myopathies and muscular dystrophy. Necrotic fibers lost their reactivity for both filaments. Type II glycogenosis showed an increased reactivity for desmin and vimentin. A mild increase in desmin and vimentin staining intensity was observed in the atrophic cells of spinal muscular atrophy, but not in the atrophic fibers from other disease entities. Weader reactivity for desmin was noted in atrophic cells of myotonic dystrophy. The immunohistochemical study of desmin and vimentin in neuromuscular disorders is helpful in detecting degeneration, or regeneration changes, of muscle fibers and may provide clues to the pathogenesis of various muscular disorders.#130

Selective Enhancement of L-Type Calcium Currents by Corticotropin in Acutely Isolated Rat Amygdala Neurons

ABSTRACT The modulation of voltage-dependent calcium currents (I Ca ) by corticotropin was studied in acutely dissociated rat amygdala neurons using whole-cell, patch-clamp recording techniques. Application of corticotropin or corticotropin 4 -10 increased I Ca in a concentration-dependent manner, with half-maximal effective concentrations of 65 and 176 nM and maximal increases of ϳ75% and ϳ50%, respectively. Nimodipine (1 M) reduced the I Ca by ϳ30%. Subsequent application of corticotropin in the presence of nimodipine failed to produce an enhancement of I Ca , suggesting that corticotropin acts selectively on L-type channels. In addition, corticotropin-mediated enhancement of I Ca after exposure to -conotoxin-GVIA and -agatoxin-IV was not significantly different from that observed in the control neurons, ruling out the involvement of N-and P/Q-type channels. The effect of corticotropin was mimicked by forskolin and (S p )-cyclic adenosine 3Ј,5Ј-monophosphothioate [(S p )-cAMPS] and was significantly enhanced in the presence of phosphodiesterase or protein phosphatase inhibitors. On the other hand, the effect of corticotropin was markedly reduced in neurons intracellularly dialyzed with (R p )-cAMPS, a regulatory site antagonist of cAMP-dependent protein kinase (PKA) or by extracellular perfusion of KT 5720, a catalytic site antagonist of PKA. Taken together, these results show for the first time that corticotropin enhances voltage-dependent Ca 2ϩ currents in brain neurons and that this increase is mediated through L-type channels and involves a cAMP-dependent mechanism. During stress or psychiatric disturbance, corticotropin, a 39-amino-acid polypeptide, is released from the anterior pituitary in response to corticoliberin stimulation. Corticotropin then acts on zona fasciculata cells of the adrenal cortex to activate steroidogenesis and stimulate cortisol secretion The amygdala plays a key role in the modulation of endocrine function, visceral effector mechanisms, and complex patterns of integrated behavior such as defense, aggregation, epilepsy, learning, and memor