The degree to which apparent amnesic effects of various centrally acting drugs are secondary to their effects on arousal remains a contentious issue. The present study uses two methods to dissociate memory and arousal effects of the cholinergic antagonist, scopolamine (SP), and the GABA-A/benzodiazepine receptor agonist, lorazepam (LZ). First, it compared their effects to those of an antihistamine, diphenhydramine (DPh), to provide an active control for arousal reduction. Second, it used the same measure--event-related potentials (ERPs)--as as a parallel index of both the arousal and cognitive effects of the drugs. Fifty participants were allocated to one of five parallel treatment groups (0.6 mg SP; 2 mg LZ; 25, 50 mg DPh; placebo). ERPs were recorded during a continuous word recognition task as well as during an "oddball" task. SP, LZ and 50 mg DPh produced a similar profile of effects on certain indices of arousal and on early components of ERPs. However, SP and LZ (but not DPh) produced marked impairments of episodic memory, and this pattern was similar to that on later components of ERPs. Memory impairments by SP and LZ were highly significant on retention in the continuous recognition task and further, no drug effects were found on response bias. Subsequent free recall was similarly very impaired by SP and LOR but not by the antihistamine. We conclude that benzodiazepines and anticholinergic drugs both reduce arousal and induce amnesia, but these effects are not interdependent. Our findings provide strong evidence for a dissociation between the effects on episodic memory and on arousal of these centrally acting compounds.
In the acute experiment six healthy volunteers were given orally two doses of lithium chloride, 16 and 32 mmol, and placebo sodium chloride 32 mmol in a double-blind standardized procedure, with a 1-week interval between treatments. Compared to sodium, lithium produced a decrease in subjective well-being, decrease of skin conductance fluctuations, and increase in plasma calcium concentrations. Dose-related effects were maximal at the first hour after ingestion, decreasing or disappearing at 3--5 h. Most effects did not correlate with plasma or erythrocyte lithium concentrations, but drug effects and feelings of nausea were highly correlated. Accordingly, most acute effects seemed due to peripheral drug effects. In the chronic experiment six healthy volunteers were given orally 16 mmol of lithium chloride or sodium chloride (placebo) twice a day for 1 week in a double-blind standardized procedure with a 2-week interval between treatment weeks. Compared to placebo, lithium produced feelings of subjective impairment, an increase in EEG slow waves and of auditory evoked response variability, a deficit in long-term memory, and an increase in plasma magnesium concentrations. Most lithium effects did not correlate with plasma or erythrocyte lithium concentrations.
Clubroot (Plasmodiophora brassicae) is an important disease of canola (Brassica napus) and other brassica crops. Accurate estimation of inoculum load in soil is important for evaluating producer risk in planting a susceptible crop, but also for evaluation of management practices such as crop rotation. This study compared five molecular techniques for estimating P. brassicae resting spores in soil: quantitative polymerase chain reaction (qPCR), competitive positive internal control PCR (CPIC‐PCR), propidium monoazide PCR (PMA‐PCR), droplet digital PCR (ddPCR) and loop‐mediated isothermal DNA amplification (LAMP). For ddPCR and LAMP, calibrations were developed using spiked soil samples. The comparison was carried out using soil samples collected from a long‐term rotation study at Normandin, Québec, with replicated plots representing 0‐, 1‐, 2‐, 3‐, 5‐ and 6‐year breaks following susceptible canola infested with clubroot. CPIC‐PCR and ddPCR provided repeatable estimates of resting spore numbers in soil compared with estimates from qPCR or LAMP alone. CPIC‐PCR provided the most robust measurement of spore concentration, especially in the 2 years following a crop of susceptible canola, because it corrected for effects of PCR inhibitors. PMA‐PCR demonstrated that a large proportion of the DNA of P. brassicae detected in soil after the susceptible canola crop was derived from spores that were immature or otherwise not viable. Each assay provided a similar pattern of spore concentration in soil, which supported the conclusion of a previous study at this site that resting spore numbers declined rapidly in the first 2 years after a susceptible crop, but much more slowly subsequently.
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