A deficiency in pejvakin, a protein of unknown function, causes a strikingly heterogeneous form of human deafness. Pejvakin-deficient (Pjvk(-/-)) mice also exhibit variable auditory phenotypes. Correlation between their hearing thresholds and the number of pups per cage suggest a possible harmful effect of pup vocalizations. Direct sound or electrical stimulation show that the cochlear sensory hair cells and auditory pathway neurons of Pjvk(-/-) mice and patients are exceptionally vulnerable to sound. Subcellular analysis revealed that pejvakin is associated with peroxisomes and required for their oxidative-stress-induced proliferation. Pjvk(-/-) cochleas display features of marked oxidative stress and impaired antioxidant defenses, and peroxisomes in Pjvk(-/-) hair cells show structural abnormalities after the onset of hearing. Noise exposure rapidly upregulates Pjvk cochlear transcription in wild-type mice and triggers peroxisome proliferation in hair cells and primary auditory neurons. Our results reveal that the antioxidant activity of peroxisomes protects the auditory system against noise-induced damage.

No abstract

No abstract

Although interactions between backpropagating action potentials and synaptic stimulations have been extensively studied in pyramidal neurons, dendritic propagation and the summation of these signals in interneurons are not nearly as well known. In this study, twophoton imaging was used to explore the basic properties of dendritic calcium signaling in CA1 stratum radiatum interneurons. In contrast to hippocampal pyramidal neurons, the backpropagating action potential-evoked calcium transients in dendrites of interneurons underwent a distance-dependent increment. Although, in proximal dendrites, an increment could be attributed to a smaller dendrite diameter, distal dendrites did not show such dependence. Calcium responses in interneurons had a smaller amplitude, slower rise time, and decay than in pyramidal neurons. To explore the factors underlying the difference, we compared the calcium-binding capacity in interneurons and in pyramidal neurons. Our finding that endogenous calcium buffers had a higher level in interneurons may primarily explain the different kinetics and amplitudes of calcium transients. Synaptic stimulation-evoked calcium transients were also larger at distant dendritic locations. The spread of these signals was restricted to 12-13 m long dendritic compartments. Supporting the reported lack of long-term potentiation in these interneurons, we found only sublinear or linear summations of calcium responses to coincident synaptic inputs and backpropagating spikes.

Two-photon laser scanning microscopy was used to correlate electrical events detected with whole-cell somatic recordings to Ca

Although dendritic spikes are generally thought to be restricted to the distal apical dendrite, we know very little about the possible modulatory mechanisms that set the spatial limits of dendritic spikes. Our experiments demonstrated that high-frequency trains of backpropagating action potentials avoided filtering in the apical dendrite and initiated all-or-none dendritic Ca(2+) transients associated with dendritic spikes in layer 5 pyramidal neurons of the prefrontal cortex. The block of hyperpolarization-activated currents (I(h)) by ZD7288 could shift the frequency threshold and decreased the number of action potentials required to produce the all-or-none Ca(2+) transient. Activation of alpha(2)-adrenergic receptors could also shift the frequency domain of spike induction to lower frequencies. Our data suggest that noradrenergic activity in the prefrontal cortex influences dendritic I(h) and extends the zone of dendritic spikes in the apical dendrite via alpha(2)-adrenergic receptors. This mechanism might be one cellular correlate of the alpha(2)-receptor-mediated actions on working memory.

No abstract

To produce a prolonged decrease m blood pressure, we have developed a nonpathogenic adeno-associated viral vector (AAV) with the antIsense DNA for AT1-R AAV has many advantages over other viral vectors AAV does not stimulate mflammallon or immune reaction AAV enters nondtvlchng cells and does not replicate Therefore, it IS an appropriate choice for gene therapy Recombinant AAV was prepared with a cassette contaumg a cytomegalovtrus promoter and the cDNA for the AT, receptor inserted m the annsense dire&on The cassette was packaged ohgonucleotides, directed to either AT,-R mRNA or to anglotensmogen mRNA, slgmfscantly reduce blood pressure m hypertensive animals with a single mJection mto the bram I-3 Although the adn-nmstration of antisense m the brain proved that antlsense can reduce high blood pressure of neurogemc orlgm, it obviously 1s not an acceptable route for treatment of human hypertension To demonstrate that antisense acts via a systemic route of delivery, we have shown that antisense delivered mtravenously4 or mtra-arterially5 can also reduce blood pressure m hypertensive rats. Antisense AT1 mRNA significantly decreased the blood pressure m 2&idney, 1 clip rats, m which circulating remn-Ang levels are high 4 Anglotensmogen mRNA-directed antIsense ohgonucleotide, in a hposome carrier inJected mtravenously m SHR, also decreased hypertension 5 The uptake of antisense was predommantly m the hver, as shown by fluorescent-tagged antisense. A sm-nlar approach was taken by Tomlta et al," who prepared three angiotensmogen mRNA-directed antisense ohgonucleotides and delivered them m hposomes and Sendal virus by direct mJectlon mto the hepatlc portal vem They also noted a decrease m blood pressure m SHR While these results have been encouraging for the use of antisense as a poFrom the Department of Physiology, College of Medicine, Unlversity of Florlda, Gamesvllle, Fla, and Harvard Medical School (P W ), Boston, MassCorrespondence to Dr M I Pixlhps, Department of Physiology, College of Medicine, Utuverslty of Flonda, Gamesvllle, FL 32610 E-mad MIP@phys med ufl edu 0 1997 American Heart Assoclatron, Inc tential treatment of hypertension, the maximum effectlveness of a single injection lasts for 7 days. Although this 1s Impressively longer than the response to a single dose of any antlhypertenslve drug currently available, it 1s our hope that we can extend the effectiveness of the antisense approach by delivering antisense m a viral vector that will produce a prolonged reduction m blood pressure for weeks or months There are several vu-al vectors to choose from, mcludmg retrovlruses, adenovlrus, herpes virus, polo virus, and AAV All have disadvantages and some advantages, but the AAV offers the most attractive advantages and the fewest disadvantages AAV 1s safe to use It does not induce any pathogenic response and does not replicate mslde cells The AAV 1s a defective parvovlrus and cannot replicate m cells without the presence of wild-type adenovlrus 73 The AAV IS effective as a vector because it either mt...