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Re-exposure of rats to a previously fear-conditioned environment arouses great alterations in behavioral and cardiovascular parameters. Pieces of works provide putative evidence for the contribution of the dorsal hippocampus (dHC) to contextual conditioning. dHC gathers massive cholinergic inputs from the basal forebrain, and dHC acetylcholine (ACh) is often described as triggering the retrieval of defensive behavior. ACh acts partially through muscarinic receptors (mAChRs) M1R and M3R subtypes. Hence, activation of mAChRs facilitates autonomic and behavioral responses associated with threats and dangers. Therefore, this study explored the likely involvement of M1R and M3R in rat dHC to establish the behavioral and autonomic changes associated with contextual fear retrieval. Male Wistar rats had stainless steel guide cannula implanted into the dHC before being submitted to contextual fear conditioning (6 footshocks, 1.5 mA, 3 s). A catheter placed within the femoral artery allowed autonomic recordings. A variety of drugs were delivered into the dHC 10 min before contextual re-exposure. The choline reuptake inhibitor hemicholinium induced a decrease of the fear conditioned responses, while did not modify it in non-conditioned animals. The non-selective mAChR antagonist atropine also reduced the fear-conditioned responses, as did the selective M1/M3 mAChRs antagonist fumarate. On the other hand, the M1 selective mAChR antagonist pirenzepine inhibited all the autonomic fear responses without affecting animal freezing. These findings support that cholinergic neurotransmission present in the dHC acts through mAChRs to coordinate the expression of fear evoked by contextual conditioning., (Copyright © 2022 Elsevier Inc. All rights reserved.)

The objective of this study was to evaluate Cr toxicity in young plants of the CCN 51 Theobroma cacao genotype at different concentrations of Cr 3+ in the soil (0, 100, 200, 400 and 600 mg kg -1 ) through physiological, ultrastructural, antioxidant and molecular changes. Doses of 400 and 600 mg Cr 3+ kg -1 soil severely affected foliar gas exchange, promoted by damages in photosynthetic machinery evidenced by the decrease in CO 2 fixation. Decreased expression of psbA and psbO genes, changes in enzymatic activity and lipid peroxidation also affected leaf gas exchange. A hormesis effect was observed at 100 mg Cr 3+ kg -1 soil for the photosynthetic activity. As a metal exclusion response, the roots of the cocoa plants immobilized, on average, 75% of the total Cr absorbed. Ultrastructural changes in leaf mesophyll and roots, with destruction of mitochondria, plasmolysis and formation of vesicles, were related to the oxidative stress promoted by excess ROS. The activity of the antioxidant enzymes SOD, APX, GPX and CAT and the amino acid proline coincided with the greater expression of the sod cyt gene demonstrating synchronicity in the elimination of ROS. It was concluded, therefore, that the tolerance of the cocoa plants to the toxicity of Cr 3+ depends on the concentration and time of exposure to the metal. Higher doses of Cr 3+ in the soil promoted irreversible damage to the photosynthetic machinery and the cellular ultrastructure, interfering in the enzymatic and non-enzymatic systems related to oxidative stress and gene expression. However, the low mobility of the metal to the leaf is presented as a strategy of tolerance to Cr 3+ ., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Insecticide resistance is one of the main problems in vector control programs. Because insects have developed resistance to all classes of available chemical insecticides, a proper surveillance and management of resistance in areas where these compounds are being utilized is crucial for the success of control programs. Since the mechanisms and molecular bases of resistance are various, they must be characterized to allow efficient monitoring strategies. Here we report the establishment of an Aedes aegypti strain resistant to temephos, named RecR, selected under laboratory conditions. The parental A. aegypti population was obtained from eggs collected in an area where temephos had been used for 8 years, and presented a baseline resistance ratio (RR) of 7. After 17 generations under selective pressure, the RR has increased to 180. Biochemical assays indicate that metabolic mechanisms are involved on temephos resistance in the selected strain. These experiments showed that, compared to the susceptible colony Rockefeller, RecR present higher activity of glutathione S-transferases (GSTs), alpha- and beta-esterases, and, to a lesser degree, mixed function oxidases (MFO). At the 14th or 17th generations, there was no cross resistance of these insects to deltamethrin, cypermethrin and malathion, while a low resistance level (RR=3) was observed for pyriproxyfen, a juvenile hormone analogue. Experiments on resistance reversal, performed through three different field simulated schemes using the resistant strain, showed that temephos susceptibility can be recovered. The establishment of an A. aegypti colony resistant to temephos is extremely valuable for a deeper understanding of resistance mechanisms and thus for further improvements in control strategies against this vector. With the urgent need on improving methodologies to monitor resistance, molecular studies such as microarrays, and resistant colonies such as RecR will certainly hasten such studies., (Copyright 2009 Elsevier B.V. All rights reserved.)