Role of nitric oxide on defensive behavior and long-term aversive learning induced by chemical stimulation of the dorsolateral periaqueductal gray matter.

The midbrain periaqueductal gray matter, especially the dorsolateral portion (dlPAG), coordinates immediate defensive responses (DR) to threats, but also ascends forebrain information for aversive learning. The synaptic dynamics in the dlPAG regulate the intensity and type of behavioral expression, as well as long-term processes such as memory acquisition, consolidation, and retrieval. Among several neurotransmitters and neural modulators, nitric oxide seems to play an important regulatory role in the immediate expression of DR, but it remains unclear if this gaseous on-demand neuromodulator contributes to aversive learning. Therefore, the role of nitric oxide in the dlPAG was investigated, during conditioning in an olfactory aversive task. The behavioral analysis consisted of freezing and crouch-sniffing in the conditioning day after glutamatergic NMDA agonist injection into the dlPAG. Two days later, rats were re-exposed to the odor cue and avoidance was measured. 7NI, a selective neuronal nitric oxide synthase inhibitor (40 and 100 nmol), injected before NMDA (50 pmol) impaired immediate DR and consequent aversive learning. The scavenging of extrasynaptic nitric oxide by C-PTIO (1 and 2 nmol) induced similar results. Moreover, spermine NONOate, a nitric oxide donor (5, 10, 20, 40, and 80 nmol), produced DR by itself, but only the low dose also promoted learning. The following experiments utilized a fluorescent probe, DAF-FM diacetate (5 µM), directly into the dlPAG, to quantify nitric oxide in the three previous experimental situations. Nitric oxide levels were increased after NMDA stimulation, decreased after 7NI, and increased after spermine NONOate, in line with alterations in defensive expression. Altogether, the results indicate that nitric oxide plays a modulatory and decisive role in the dlPAG regarding immediate DR and aversive learning.

The Chemical Environment at Maturation Stage in Pinus spp. Somatic Embryogenesis: Implications in the Polyamine Profile of Somatic Embryos and Morphological Characteristics of the Developed Plantlets.

Changes in the chemical environment at the maturation stage in Pinus spp. somatic embryogenesis will be a determinant factor in the conversion of somatic embryos to plantlets. Furthermore, the study of biochemical and morphological aspects of the somatic embryos could enable the improvement of somatic embryogenesis in Pinus spp. In the present work, the influence of different amino acid combinations, carbohydrate sources, and concentrations at the maturation stage of Pinus radiata D. Don and Pinus halepensis Mill. was analyzed. In P. radiata, the maturation medium supplemented with 175 mM of sucrose and an increase in the amino acid mixture (1,100 mgL-1 of L-glutamine, 1,050 mgL-1 of L-asparagine, 350 mgL-1 of L-arginine, and 35 mgL-1 of L-proline) promoted bigger embryos, with a larger stem diameter and an increase in the number of roots in the germinated somatic embryos, improving the acclimatization success of this species. In P. halepensis, the maturation medium supplemented with 175 mM of maltose improved the germination of somatic embryos. The increase in the amount of amino acids in the maturation medium increased the levels of putrescine in the germinated somatic embryos of P. halepensis. We detected significant differences in the amounts of polyamines between somatic plantlets of P. radiata and P. halepensis; putrescine was less abundant in both species. For the first time, in P. radiata and P. halepensis somatic embryogenesis, we detected the presence of cadaverine, and its concentration changed according to the species.

Periaqueductal gray glutamatergic, cannabinoid and vanilloid receptor interplay in defensive behavior and aversive memory formation.

Stimulation of the midbrain periaqueductal gray matter (PAG) in humans elicits sensations of fear and impending terror, and mediates predator defensive responses in rodents. In rats, pharmacological stimulation of the dorsolateral portion of the PAG (dlPAG) with N-Methyl-d-Aspartate (NMDA) induces aversive conditioning that acts as an unconditioned stimulus (US). In the present work, we investigated the interplay between the vanilloid TRPV1 and cannabinoid CB1 receptors in the NMDA-dlPAG defensive response and in subsequent aversive learning. Rats were subjected to dlPAG NMDA infusion in an olfactory conditioned stimulus (CS) task allowing the evaluation of immediate and long-term defensive behavioral responses during CS presentation. The results indicated that an intermediate dose of NMDA (50 pmol) induced both immediate and long-term effects. A sub-effective dose of NMDA (25 pmol) was potentiated by the TRPV1 receptor agonist capsaicin (CAP, 1 nmol) and the CB1 receptor antagonist, AM251 (200 pmol). CAP (10 nmol) or the combination of CAP (1 nmol) and AM251 (200 pmol) induced long-term effects without increasing immediate defensive responses. The glutamate release inhibitor riluzole (2 or 4 nmol) and the AMPA/kainate receptor antagonist DNQX (2 or 4 nmol) potentiated the immediate effects but blocked the long-term effects. The results showed that immediate defensive responses rely on NMDA receptors, and aversive learning on the fine-tuning of TRPV1, CB1, metabotropic glutamate and AMPA receptors located in pre- and postsynaptic membranes. In conclusion, the activity of the dlPAG determines core affective aspects of aversive memory formation controlled by local TRPV1/CB1 balance.

Dictator's Game and Prisoner's Dilemma in an EEG study on money donation

Knowledge is currently scarce about what happens in the brain when a decision is made to make a donation. This intriguing donation behavior is often assumed to relate to social relationships. The present study used simulated situations in which participants had to decide how to manage money when possibilities for donation were available. Electroencephalographic signals were recorded while participants were exposed to two cognitive situations, the Dictator's Game and the Prisoner's Dilemma, to simulate money exchange between people. Brain activity was measured to determine whether correlations could be made with decisions to donate. Sixty volunteers were assessed, and stimuli were presented randomly. After the presentation of the cognitive tests, the participants were allocated to two groups for the respective cognitive situations. The data showed significant differences in the left prefrontal cortex between questions with a donation context and questions not related to donations. Participants who heard a question related to donation had higher activation in the left prefrontal cortex. These results are consistent with recent functional magnetic resonance imaging studies, suggesting that greater activation in the prefrontal cortex could be produced by the logical evaluation of dilemmas. These results suggest that logical evaluation occurs when faced with a reasonable donation situation.

Dictator's Game and Prisoner's Dilemma in an EEG study on money donation

Knowledge is currently scarce about what happens in the brain when a decision is made to make a donation. This intriguing donation behavior is often assumed to relate to social relationships. The present study used simulated situations in which participants had to decide how to manage money when possibilities for donation were available. Electroencephalographic signals were recorded while participants were exposed to two cognitive situations, the Dictator's Game and the Prisoner's Dilemma, to simulate money exchange between people. Brain activity was measured to determine whether correlations could be made with decisions to donate. Sixty volunteers were assessed, and stimuli were presented randomly. After the presentation of the cognitive tests, the participants were allocated to two groups for the respective cognitive situations. The data showed significant differences in the left prefrontal cortex between questions with a donation context and questions not related to donations. Participants who heard a question related to donation had higher activation in the left prefrontal cortex. These results are consistent with recent functional magnetic resonance imaging studies, suggesting that greater activation in the prefrontal cortex could be produced by the logical evaluation of dilemmas. These results suggest that logical evaluation occurs when faced with a reasonable donation situation.(AU)