PNU-120596, a positive allosteric modulator of α7 nicotinic acetylcholine receptors, reverses a sub-chronic phencyclidineinduced cognitive deficit in the attentional set-shifting task in female rats

yThe α7 nicotinic acetylcholine receptors (nAChRs) have been highlighted as a target for cognitive enhancement in schizophrenia. Adult female hooded Lister rats received sub-chronic phencyclidine (PCP) (2mg/kg) or vehicle i.p. twice daily for 7 days, followed by 7 days’ washout. PCP-treated rats then received PNU-120596 (10mg/kg; s.c.) or saline and were tested in the attentional set-shifting task. Sub-chronic PCP produced a significant cognitive deficit in the extra-dimensional shift (EDS) phase of the task (p < 0.001, compared with vehicle). PNU-120596 significantly improved performance of PCP-treated rats in the EDS phase of the attentional set-shifting task (p < 0.001). In conclusion, these data demonstrate that PNU-120596 improves cognitive dysfunction in our animal model of cognitive dysfunction in schizophrenia, most likely via modulation of α7 nACh receptors.This work was partially funded by Johnson & Johnson Pharmaceutical Research and Development

Concordance of Alzheimer's Disease-Related Biomarkers Between Intraventricular and Lumbar Cerebrospinal Fluid in Idiopathic Normal Pressure Hydrocephalus

BACKGROUND: Alzheimer's disease cerebrospinal fluid (CSF) biomarkers amyloid-β 1-42 (Aβ42), total tau (T-tau), and phosphorylated tau 181 (P-tau181) are widely used. However, concentration gradient of these biomarkers between intraventricular (V-CSF) and lumbar CSF (L-CSF) has been demonstrated in idiopathic normal pressure hydrocephalus (iNPH), potentially affecting clinical utility. OBJECTIVE: Here we aim to provide conversion factors for clinical and research use between V-CSF and L-CSF. METHODS: Altogether 138 iNPH patients participated. L-CSF samples were obtained prior to shunt surgery. Intraoperative V-CSF samples were obtained from 97 patients. Post-operative follow-up L- and V-CSF (shunt reservoir) samples of 41 patients were obtained 1-73 months after surgery and then after 3, 6, and 18 months. CSF concentrations of Aβ42, T-tau, and P-tau181 were analyzed using commercial ELISA assays. RESULTS: Preoperative L-CSF Aβ42, T-tau, and P-tau181 correlated to intraoperative V-CSF (ρ= 0.34-0.55, p < 0.001). Strong correlations were seen between postoperative L- and V-CSF for all biomarkers in every follow-up sampling point (ρs Aβ 42: 0.77-0.88, T-tau: 0.91-0.94, P-tau181: 0.94-0.96, p < 0.0001). Regression equations were determined for intraoperative V- and preoperative L-CSF (Aβ 42: V-CSF = 185+0.34*L-CSF, T-tau: Ln(V-CSF) = 3.11+0.49*Ln(L-CSF), P-tau181: V-CSF = 8.2+0.51*L-CSF), and for postoperative V- and L-CSF (Aβ 42: V-CSF = 86.7+0.75*L-CSF, T-tau: V-CSF = 86.9+0.62*L-CSF, P-tau181: V-CSF = 2.6+0.74*L-CSF). CONCLUSION: Aβ 42, T-tau, and P-tau181 correlate linearly in-between V- and L-CSF, even stronger after CSF shunt surgery. Equations presented here, provide a novel tool to use V-CSF for diagnostic and prognostic entities relying on the L-CSF concentrations and can be applicable to clinical use when L-CSF samples are not available or less invasively obtained shunt reservoir samples should be interpreted

Time Trends of Cerebrospinal Fluid Biomarkers of Neurodegeneration in Idiopathic Normal Pressure Hydrocephalus

Background: Longitudinal changes in cerebrospinal fluid (CSF) biomarkers are seldom studied. Furthermore, data on biomarker gradient between lumbar (L-) and ventricular (V-) compartments seems to be discordant. Objective: To examine alteration of CSF biomarkers reflecting Alzheimer's disease (AD)-related amyloid-beta (A beta) aggregation, tau pathology, neurodegeneration, and early synaptic degeneration by CSF shunt surgery in idiopathic normal pressure hydrocephalus (iNPH) in relation to AD-related changes in brain biopsy. In addition, biomarker levels in L- and V-CSF were compared. Methods: L-CSF was collected prior to shunt placement and, together with V-CSF, 3-73 months after surgery. Thereafter, additional CSF sampling took place at 3, 6, and 18 months after the baseline sample from 26 iNPH patients with confirmed A beta plaques in frontal cortical brain biopsy and 13 iNPH patients without A beta pathology. CSF Amyloid-beta(42) (A beta(42)), total tau (T-tau), phosphorylated tau (P-tau(181)), neurofilament light (NFL), and neurogranin (NRGN) were analyzed with customized ELISAs. Results: All biomarkers but A beta(42) increased notably by 140-810% in L-CSF after CSF diversion and then stabilized. A beta(42) instead showed divergent longitudinal decrease between A beta-positive and -negative patients in L-CSF, and thereafter increase in A beta-negative iNPH patients in both L- and V-CSF. All five biomarkers correlated highly between V-CSF and L-CSF (A beta(42) R = 0.87, T-tau R = 0.83, P-tau R = 0.92, NFL R = 0.94, NRGN R = 0.9; all p < 0.0001) but were systematically lower in V-CSF (A beta(42) 14 %, T-tau 22%, P-tau 20%, NFL 32%, NRGN 19%). With APOE genotype-grouping, only A beta(42) showed higher concentration in non-carriers of allele epsilon 4. Conclusion: Longitudinal follow up shows that after an initial post-surgery increase, T-tau, P-tau, and NRGN are stable in iNPH patients regardless of brain biopsy A beta pathology, while NFL normalized toward its pre-shunt levels. A beta(42) as biomarker seems to be the least affected by the surgical procedure or shunt and may be the best predictor of AD risk in iNPH patients. All biomarker concentrations were lower in V-than L-CSF yet showing strong correlations.Peer reviewe

Studies into the functional properties of the Pharyngeal Muscle of Caenorhavditis Elegans

Caenorhabditis elegans is a well described nematode employed as a genetic model organism for studies into function, differentiation, development, and morphology of simple nervous and muscular systems. However, essential information regarding its physiology and pharmacology are lacking. To address this, electrophysiological recording techniques from pharyngeal muscle cells were developed to determine the ionic basis of the resting membrane potential and action potential. Resting membrane potential of pharyngeal muscle cells were relatively unaffected by changes in the extracellular concentrations of Cl-, Na+ or Ca++. However, variations in extracellular concentrations of K+, or exposure to ouabain, both elicited a depolarisation, although the depolarisations observed during elevations of extracellular K+ were less than would be predicted if the membrane potential were completely dependent on K+. It can be concluded therefore, that the resting membrane potential is largely determined by a K+ permeability, and a ouabain-sensitive, electrogenic pump. Action potential height was reduced or increased in concentration-dependent manner following exposure to low or high extracellular Ca++ concentrations respectively. Furthermore, the L-type Ca++ channel blockers, verapamil and nifedipine, both reduced action potential amplitude and duration. This suggests a role for an L-type Ca++ channel in the action potential. However, action potentials persisted in Ca++ free saline. Action potential duration increased or decreased in a concentration-dependent manner following exposure to low or high Ca++ concentrations respectively. This suggests that the repolarisation phase is partly determined by a Ca++ activated K+ channel. Possibly the most surprising finding was the absolute dependence of pharyngeal action potential generation on extracellular Na+ concentration, especially as extensive searches of the C. elegans genome have failed to find any obvious candidate for a voltage-gated Na+ channel.</p

Characterization of glutamate-gated chloride channels in the pharynx of wild-type and mutant Caenorhabditis elegans delineates the role of the subunit GluCl-alpha 2 in the function of the native receptor

Glutamate-gated chloride (GluCl) channels are the site of action of the anthelmintic ivermectin. Previously, the Xenopus laevis oocyte expression system has been used to characterize GluCl channels cloned from Caenorhabditis elegans. However, information on the native, pharmacologically relevant receptors is lacking. Here, we have used a quantitative pharmacological approach and intracellular recording techniques of C. elegans pharynx to characterize them. The glutamate response was a rapidly desensitizing, reversible, chloride-dependent depolarization (EC50 = 166 µM), only weakly antagonized by picrotoxin. The order of potency of agonists was ibotenate &gt; L-glutamate &gt; kainate = quisqualate. Ivermectin potently and irreversibly depolarized the muscle (EC50 = 2.7 nM). No further depolarization was seen with coapplication of maximal glutamate during the maximal ivermectin response, indicating that ivermectin depolarizes the muscle by the same ionic mechanism as glutamate (i.e., chloride). The potency of ivermectin on the pharynx was greater than at any of the GluCl subunits expressed in X. laevis oocytes. This effect of ivermectin was abolished in the mutant avr-15, which lacks a functional GluCl-alpha 2 subunit. However, a chloride-dependent, nondesensitizing response to glutamate persisted. Therefore, the GluCl-alpha 2 subunit confers ivermectin sensitivity and a high-affinity desensitizing glutamate response on the native pharyngeal GluCl receptor

Synaptic transmission changes in fear memory circuits underlie key features of an animal model of schizophrenia.

Non-competitive antagonists of the N-methyl-d-aspartate receptor (NMDA) such as phencyclidine (PCP) elicit schizophrenia-like symptoms in healthy individuals. Similarly, PCP dosing in rats produces typical behavioral phenotypes that mimic human schizophrenia symptoms. Although schizophrenic behavioral phenotypes of the PCP model have been extensively studied, the underlying alterations of intrinsic neuronal properties and synaptic transmission in relevant limbic brain microcircuits remain elusive. Acute brain slice electrophysiology and immunostaining of inhibitory neurons were used to identify neuronal circuit alterations of the amygdala and hippocampus associated with changes in extinction of fear learning in rats following PCP treatment. Subchronic PCP application led to impaired long-term potentiation (LTP) and marked increases in the ratio of NMDA to 2-amino-3(5-methyl-3-oxo-1,2-oxazol-4-yl)propionic acid (AMPA) receptor-mediated currents at lateral amygdala (LA) principal neurons without alterations in parvalbumin (PV) as well as non-PV, glutamic acid decarboxylase 67 (GAD 67) immunopositive neurons. In addition, LTP was impaired at the Schaffer collateral to CA1 hippocampal pathway coincident with a reduction in colocalized PV and GAD67 immunopositive neurons in the CA3 hippocampal area. These effects occurred without changes in spontaneous events or intrinsic membrane properties of principal cells in the LA. The impairment of LTP at both amygdalar and hippocampal microcircuits, which play a key role in processing relevant survival information such as fear and extinction memory concurred with a disruption of extinction learning of fear conditioned responses. Our results show that subchronic PCP administration in rats impairs synaptic functioning in the amygdala and hippocampus as well as processing of fear-related memories.info:eu-repo/semantics/publishe

Ionic basis of the resting membrane potential and action potential in the pharyngeal muscle of Caenorhabditis elegans

The pharynx of C. elegans is a rhythmically active muscle that pumps bacteria into the gut of the nematode. This activity is maintained by action potentials, which qualitatively bear a resemblance to vertebrate cardiac action potentials. Here, the ionic basis of the resting membrane potential and pharyngeal action potential has been characterized using intracellular recording techniques. The resting membrane potential is largely determined by a K+ permeability, and a ouabain-sensitive, electrogenic pump. As previously suggested, the action potential is at least partly dependent on voltage-gated Ca2+ channels, as the amplitude was increased as extracellular Ca2+ was increased, and decreased by L-type Ca2+ channel blockers verapamil and nifedipine. Barium caused a marked prolongation of action potential duration, suggesting that a calcium-activated K+ current may contribute to repolarization. Most notably, however, we found that action potentials were abolished in the absence of external Na+. This may be due, at least in part, to a Na+-dependent pacemaker potential. In addition, the persistence of action potentials in nominally free Ca2+, the inhibition by Na+ channel blockers procaine and quinidine, and the increase in action potential frequency caused by veratridine, a toxin that alters activation of voltage-gated Na+ channels, point to the involvement of a voltage-gated Na+ current. Voltage-clamp analysis is required for detailed characterization of this current, and this is in progress. Nonetheless, these observations are quite surprising in view of the lack of any obvious candidate genes for voltage-gated Na+ channels in the C. elegans genome. It would therefore be informative to re-evaluate the data from these homology searches, with the aim of identifying the gene(s) conferring this Na+, quinidine, and veratridine sensitivity to the pharynx