Systemic delivery of pharmacologic agents has led to many significant advances in the treatment of neurologic and psychiatric conditions. However, this approach has several limitations, including difficulty penetrating the blood-brain barrier and enzymatic degradation prior to reaching its intended target. Here, we describe the testing of a system allowing intraparenchymal (IPa) infusion of therapeutic agents directly to the appropriate anatomical targets, in a swine model.
The role of ?(1)-adrenergic receptors (?(1)ARs) in cognition and mood is controversial, probably as a result of past use of nonselective agents. ?(1A)AR activation was recently shown to increase neurogenesis, which is linked to cognition and mood. We studied the effects of long-term ?(1A)AR stimulation using transgenic mice engineered to express a constitutively active mutant (CAM) form of the ?(1A)AR. CAM-?(1A)AR mice showed enhancements in several behavioral models of learning and memory. In contrast, mice that have the ?(1A)AR gene knocked out displayed poor cognitive function. Hippocampal brain slices from CAM-?(1A)AR mice demonstrated increased basal synaptic transmission, paired-pulse facilitation, and long-term potentiation compared with wild-type (WT) mice. WT mice treated with the ?(1A)AR-selective agonist cirazoline also showed enhanced cognitive functions. In addition, CAM-?(1A)AR mice exhibited antidepressant and less anxious phenotypes in several behavioral tests compared with WT mice. Furthermore, the lifespan of CAM-?(1A)AR mice was 10% longer than that of WT mice. Our results suggest that long-term ?(1A)AR stimulation improves synaptic plasticity, cognitive function, mood, and longevity. This may afford a potential therapeutic target for counteracting the decline in cognitive function and mood associated with aging and neurological disorders.
Huntingtons disease is an autosomal dominant neurodegenerative disease caused by a toxic gain of function mutation in the huntingtin gene (Htt). Silencing of Htt with RNA interference using direct CNS delivery in rodent models of Huntingtons disease has been shown to reduce pathology and promote neuronal recovery. A key translational step for this approach is extension to the larger non-human primate brain, achieving sufficient distribution of small interfering RNA targeting Htt (siHtt) and levels of Htt suppression that may have therapeutic benefit. We evaluated the potential for convection enhanced delivery (CED) of siHtt to provide widespread and robust suppression of Htt in nonhuman primates. siHtt was infused continuously for 7 or 28 days into the nonhuman primate putamen to analyze effects of infusion rate and drug concentration on the volume of effective suppression. Distribution of radiolabeled siHtt and Htt suppression were quantified by autoradiography and PCR, respectively, in tissue punches. Histopathology was evaluated and Htt suppression was also visualized in animals treated for 28 days. Seven days of CED led to widespread distribution of siHtt and significant Htt silencing throughout the nonhuman primate striatum in an infusion rate and dose dependent manner. Htt suppression at therapeutic dose levels was well tolerated by the brain. A model developed from these results predicts that continuous CED of siHtt can achieve significant coverage of the striatum of Huntingtons disease patients. These findings suggest that this approach may provide an important therapeutic strategy for treating Huntingtons disease.
In the precedence effect, sounds emanating directly from the source are localized preferentially over their reflections. Although most studies have focused on the delay between the onset of a sound and its echo, humans still experience the precedence effect when this onset delay is removed. We tested in barn owls the hypothesis that an ongoing delay, equivalent to the onset delay, is discernible from the envelope features of amplitude-modulated stimuli and may be sufficient to evoke this effect. With sound pairs having only envelope cues, owls localized direct sounds preferentially, and neurons in their auditory space-maps discharged more vigorously to them, but only if the sounds were amplitude modulated. Under conditions that yielded the precedence effect, acoustical features known to evoke neuronal discharges were more abundant in the envelopes of the direct sounds than of the echoes, suggesting that specialized neural mechanisms for echo suppression were unnecessary.
Competing predictions about the effect of social exclusion were tested by meta-analyzing findings from studies of interpersonal rejection, ostracism, and similar procedures. Rejection appears to cause a significant shift toward a more negative emotional state. Typically, however, the result was an emotionally neutral state marked by low levels of both positive and negative affect. Acceptance caused a slight increase in positive mood and a moderate increase in self-esteem. Self-esteem among rejected persons was no different from neutral controls. These findings are discussed in terms of belongingness motivation, sociometer theory, affective numbing, and self-esteem defenses.
Because of the vital role of emergency departments (EDs) in the US health care system, it is important to monitor the changes in the patient mix over time to identify existing problems and ways to improve the system. The current study aimed to identify raw and population-adjusted time trends for demographic characteristics, socioeconomic characteristics, access to care, utilization of care, and general health of ED users and heavy ED users.
Activation of G protein-coupled alpha(2) adrenergic receptors (ARs) inhibits epileptiform activity in the hippocampal CA3 region. The specific mechanism underlying this action is unclear. This study investigated which subtype(s) of alpha(2)ARs and G proteins (Galpha(o) or Galpha(i)) are involved in this response using recordings of mouse hippocampal CA3 epileptiform bursts. Application of epinephrine (EPI) or norepinephrine (NE) reduced the frequency of bursts in a concentration-dependent manner: (-)EPI > (-)NE > (+)NE. To identify the alpha(2)AR subtype involved, equilibrium dissociation constants (pK(b)) were determined for the selective alphaAR antagonists atipamezole (8.79), rauwolscine (7.75), 2-(2,6-dimethoxyphenoxyethyl)aminomethyl-1,4-benzodioxane hydrochloride (WB-4101; 6.87), and prazosin (5.71). Calculated pK(b) values correlated best with affinities determined previously for the mouse alpha(2A)AR subtype (r = 0.98, slope = 1.07). Furthermore, the inhibitory effects of EPI were lost in hippocampal slices from alpha(2A)AR-but not alpha(2C)AR-knockout mice. Pretreatment with pertussis toxin also reduced the EPI-mediated inhibition of epileptiform bursts. Finally, using knock-in mice with point mutations that disrupt regulator of G protein signaling (RGS) binding to Galpha subunits to enhance signaling by that G protein, the EPI-mediated inhibition of bursts was significantly more potent in slices from RGS-insensitive Galpha(o)(G184S) heterozygous (Galpha(o)+/GS) mice compared with either Galpha(i2)(G184S) heterozygous (Galpha(i2)+/GS) or control mice (EC(50) = 2.5 versus 19 and 23 nM, respectively). Together, these findings indicate that the inhibitory effect of EPI on hippocampal CA3 epileptiform activity uses an alpha(2A)AR/Galpha(o) protein-mediated pathway under strong inhibitory control by RGS proteins. This suggests a possible role for RGS inhibitors or selective alpha(2A)AR agonists as a novel antiepileptic drug therapy.
In echoic environments, direct sounds dominate perception even when followed by their reflections. As the delay between the direct (lead) source and the reflection (lag) increases, the reflection starts to become localizable. Although this phenomenon, which is part of the precedence effect, is typically studied with brief transients, leading and lagging sounds often overlap in time and are thus composed of three distinct segments: the "superposed" segment, when both sounds are present together, and the "lead-alone" and "lag-alone" segments, when leading and lagging sounds are present alone, respectively. Recently, it was shown that the barn owl (Tyto alba) localizes the lagging sound when the lag-alone segment, not the lead-alone segment, is lengthened. This was unexpected given the prevailing hypothesis that a leading sound may briefly desensitize the auditory system to sounds arriving later. The present study confirms this finding in humans under conditions that minimized the role of the superposed segment in the localization of either source. Just as lengthening the lag-alone segment caused the lagging sound to become more salient, lengthening the lead-alone segment caused the leading sound to become more salient. These results suggest that the neural representations of the lead and lag are independent of one another.
Echoes and sounds of independent origin often obscure sounds of interest, but echoes can go undetected under natural listening conditions, a perception called the precedence effect. How does the auditory system distinguish between echoes and independent sources? To investigate, we presented two broadband noises to barn owls (Tyto alba) while varying the similarity of the sounds envelopes. The carriers of the noises were identical except for a 2- or 3-ms delay. Their onsets and offsets were also synchronized. In owls, sound localization is guided by neural activity on a topographic map of auditory space. When there are two sources concomitantly emitting sounds with overlapping amplitude spectra, space map neurons discharge when the stimulus in their receptive field is louder than the one outside it and when the averaged amplitudes of both sounds are rising. A model incorporating these features calculated the strengths of the two sources representations on the map (B. S. Nelson and T. T. Takahashi; Neuron 67: 643-655, 2010). The target localized by the owls could be predicted from the models output. The model also explained why the echo is not localized at short delays: when envelopes are similar, peaks in the leading sound mask corresponding peaks in the echo, weakening the echos space map representation. When the envelopes are dissimilar, there are few or no corresponding peaks, and the owl localizes whichever source is predicted by the model to be less masked. Thus the precedence effect in the owl is a by-product of a mechanism for representing multiple sound sources on its map.
Coral reefs are experiencing unprecedented degradation due to human activities, and protecting specific reef habitats may not stop this decline, because the most serious threats are global (i.e., climate change), not local. However, ex situ preservation practices can provide safeguards for coral reef conservation. Specifically, modern advances in cryobiology and genome banking could secure existing species and genetic diversity until genotypes can be introduced into rehabilitated habitats. We assessed the feasibility of recovering viable sperm and embryonic cells post-thaw from two coral species, Acropora palmata and Fungia scutaria that have diffferent evolutionary histories, ecological niches and reproductive strategies. In vitro fertilization (IVF) of conspecific eggs using fresh (control) spermatozoa revealed high levels of fertilization (>90% in A. palmata; >84% in F. scutaria; P>0.05) that were unaffected by tested sperm concentrations. A solution of 10% dimethyl sulfoxide (DMSO) at cooling rates of 20 to 30°C/min most successfully cryopreserved both A. palmata and F. scutaria spermatozoa and allowed producing developing larvae in vitro. IVF success under these conditions was 65% in A. palmata and 53% in F. scutaria on particular nights; however, on subsequent nights, the same process resulted in little or no IVF success. Thus, the window for optimal freezing of high quality spermatozoa was short (?5 h for one night each spawning cycle). Additionally, cryopreserved F. scutaria embryonic cells had?50% post-thaw viability as measured by intact membranes. Thus, despite some differences between species, coral spermatozoa and embryonic cells are viable after low temperature (-196°C) storage, preservation and thawing. Based on these results, we have begun systematically banking coral spermatozoa and embryonic cells on a large-scale as a support approach for preserving existing bio- and genetic diversity found in reef systems.
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