Accumulation and decomposition of cultural residues of Theobroma grandiflorum, Paullinia cupana, Bixa orellana and forest in the southern region of Amazonas.

The litter deposited on the soil surface at various stages of decomposition is important for primary productivity that impacts the microbial communities and soil carbon storage. The objective of this study was to evaluate the accumulation and decomposition of cultural residues of Theobroma grandiflorum (Willd. ex. Spreng) Schum, Paullinia cupana (Mart.) Ducke, Bixa orellana L., and forest in the Amazon region. The study was carried out in the São Francisco settlement, Canutama in the south of Amazonas, in a randomized block experimental design, and the treatments consisted of four areas with different crops: 1 - P. cupana; 2 - T. grandiflorum; 3 - B. orellana; 4 - Native woodland area (forest), in time subdivided plots: 7, 15, 30, 60, 90, 120, 150, 180, 210, 240, 270, 300, and 330 days after the distribution of the bags in the field, all with four repetitions. To evaluate the contribution and fractions of litter, conical collectors were used in each area, and collections were performed monthly in the period from March 2020 to February 2021. The estimate of the decomposition rate of the litter was done by quantifying the loss of mass, using litter bags, which allow for a direct analysis of the rate of decay over time. The forest and P. cupana environments presented the highest litter production, and greater deposition when compared to environments cultivated with T. grandiflorum and B. orellana. The forest and B. orellana areas showed the highest speed of decomposition, while the opposite situation occurred under T. grandiflorum and P. cupana cultivation.

Acute antinociceptive effect of fish oil or its major compounds, eicosapentaenoic and docosahexaenoic acids on diabetic neuropathic pain depends on opioid system activation.

Diabetic neuropathic pain is one of the most common and debilitating complications of diabetes whose available treatments are poorly effective. Currently, omega-3 polyunsaturated fatty acids (ω-3 PUFAs) have been widely studied as a treatment of many types of pain, including inflammatory, spontaneous and neuropathic pain. However, little is known about the potential antinociceptive effect of ω-3 PUFAs (fish oil; FO or its major fatty acids, eicosapentaenoic -EPA and docosahexaenoic acids-DHA), in diabetic neuropathic pain as well as the mechanisms involved. To test, streptozotocin (STZ) -induced diabetic male Wistar rats were submitted to acute treatment with FO, EPA or DHA at the second and fourth weeks after diabetes induction (at the beginning and peak of development of mechanical allodynia, respectively). The cumulative effect of these compounds after a sub-chronic treatment for two weeks was also evaluated as well as the role of central µ-opioid receptors. It was observed that acute oral treatment with FO (0.5, 1 or 3 g/kg), EPA or DHA (100, 200 or 400 mg/kg) at the 2nd or at the 4th week after STZ significantly reverted the mechanical allodynia of diabetic animals, without altering the hyperglycemia or reduced weight gain. Moreover, the sub-chronic treatment with FO, EPA or DHA induced a sustained antinociceptive effect in diabetic animals. Intriguingly, the intrathecal treatment with a µ-opioid receptor antagonist (CTOP; 10 µg/rat) completely prevented the acute effect of FO, EPA or DHA. Taken together, our data suggest that ω-3 PUFAs may represent a promising therapeutic outcome for diabetic neuropathic pain, probably acting through the opioid system activation.

Evaluation of psychotropic drugs with a modified open field test.

The open field test used to study behavioral alterations induced by psychotropic drugs is based mainly in the defecation, ambulation, rearing and grooming presented by animals subjected to the test. Because of the criticisms raised against the defecation score as a measure of the central effects of drugs, in the present experiment a modification of the test is proposed for the rat. The main points that characterize the new procedure are: (1) defecation scores are not considered; (2) besides ambulation, rearing and grooming, immobility was also recorded; (3) the total time of observation was increased, and (4) the stimuli, usually presented simultaneously in the open field (light and noise), were presented separately. The results obtained suggest that it is possible to differentiate classes of psychotropic drugs, without taking the defecation and grooming scores into consideration. Besides stimulants that evoked a characteristic pattern of behavior, neuroleptics could be differentiated from anxiolytics. Similarities, according to the dose, between barbiturates and anxiolytics were detected. Under LSD a peculiar pattern of behavior characterized by a large reactivity to light was observed.