CB1 receptor antagonism/inverse agonism increases motor system excitability in humans

CB1 receptor is highly expressed in cerebral structures related to motor control, such as motor cortex, basal ganglia and cerebellum. In the spinal cord, the expression of CB1 receptors has also been observed in ventral motor neurons, interneurons and primary afferents, i.e., in the cells that may be part of the circuits involved in motor control. It is known that the antagonist/inverse agonist of CB1 receptors Rimonabant penetrates the blood-brain barrier and produces a broad range of central psychoactive effects in humans. Based on the occurrence of central effects in humans treated with Rimonabant and on the location of CB1 receptors, we hypothesized that the application of Rimonabant can also affect the motor system. We tested the effects of a single dose of 20mg of Rimonabant on the excitability of motor cortex and of spinal motor neurons in order to detect a possible drug action on motor system at cortical and spinal levels. For this purpose we use classical protocols of transcranial magnetic and electrical stimulation (TMS and TES). Single and paired pulse TMS and TES were used to assess a number of parameters of cortical inhibition and cortical excitability as well as of the excitability of spinal motor neurons. We demonstrated that a single oral dose of 20mg of Rimonabant can increase motor system excitability at cortical and spinal levels. This opens new avenues to test the CB1R antagonists/inverse agonists for the treatment of a number of neurological dysfunctions in which can be useful to increase the excitability levels of motor system. Virtually all the disorders characterized by a reduced output of the motor cortex can be included in the list of the disorders that can be treated using CB1 antagonists/reverse agonists (e.g. stroke, traumatic brain injury, spinal cord injury, multiple sclerosis, fatigue syndromes, parkinsonisms, etc.).

Reactive processes in gas phase Na(+)-iso-C3H7Cl collisions: experimental guided-ion-beam and ab initio studies of the reactions on the ground singlet potential surface of the system up to 12.00 eV

Reactive processes, taking place when sodium ions collide with neutral iso-C(3)H(7)Cl molecules in the 0.02-12.00 eV range of energies in the center of mass frame, have been studied using an octopole radiofrequency guided-ion-beam apparatus developed in our laboratory. A dehydrohalogenation reaction channel leading to Na(C(3)H(6))(+) formation has been observed up to 1.00 eV while another process producing NaHCl(+) continues up to 4.00 eV. Furthermore, C(3)H(7)(+) formation resulting from decomposition of the reactants, ion-molecule adducts, has also been observed as well as its decomposition into C(2)H(3)(+) on increasing collision energy. Cross-section energy dependences for all these reactions have been obtained in absolute units. The ab initio electronic structure calculations have been done at the MP2 level for the colliding system ground singlet potential surface, giving information on the reactive surface main topological features. From the surface reactants side to the products' one, different potential wells and barriers have been characterized and their connectivity along the reaction evolution has been established using the intrinsic-reaction-coordinate method, thus interpreting the dynamical evolution of the reactants' collision complex to products. Experimental results demonstrate that NaHCl(+) can be produced via different channels. Reaction rate constants at 308.2 K for both dehydrohalogenation reactions have been calculated from measured excitation functions. It has been also confirmed that the reactants adduct decomposition giving C(3)H(7)(+) and NaCl takes place on the same potential surface. A qualitative interpretation of the experimental results in terms of ab initio calculations is also given.

Spinal direct current stimulation modulates the activity of gracile nucleus and primary somatosensory cortex in anaesthetized rats

Afferent somatosensory activity from the spinal cord has a profound impact on the activity of the brain. Here we investigated the effects of spinal stimulation using direct current, delivered at the thoracic level, on the spontaneous activity and on the somatosensory evoked potentials of the gracile nucleus, which is the main entry point for hindpaw somatosensory signals reaching the brain from the dorsal columns, and of the primary somatosensory cortex in anaesthetized rats. Anodal spinal direct current stimulation (sDCS) increased the spontaneous activity and decreased the amplitude of evoked responses in the gracile nucleus, whereas cathodal sDCS produced the opposite effects. At the level of the primary somatosensory cortex, the changes in spontaneous activity induced by sDCS were consistent with the effects observed in the gracile nucleus, but the changes in cortical evoked responses were more variable and state dependent. Therefore, sDCS can modulate in a polarity-specific manner the supraspinal activity of the somatosensory system, offering a versatile bottom-up neuromodulation technique that could potentially be useful in a number of clinical applications.

GABAA receptors mediate motoneuron tonic inhibition in the turtle spinal cord

GABA(A) receptors mediating tonic inhibitory currents are present in neurons from hippocampus, cerebellum, sensory cortex and thalamus. These receptors located at peri- and extra-synaptic sites are constituted mainly by α(4/6) and α(5) subunits which confer them high affinity for GABA and low desensitization. Immunohistochemical and in vitro hybridization studies have shown the expression of these subunits, while functional studies have reported the presence of GABAergic tonic currents in spinal dorsal horn neurons. However, the presence of this inhibitory current has not been documented in motoneurons. In addition, we previously reported that the monosynaptic reflex is facilitated by furosemide, an antagonist of the α(4/6) GABA(A) receptors, without affecting the dorsal root potential, which suggests the presence of a GABAergic tonic inhibitory current in motoneurons. The aim of this work was to investigate the presence of high affinity GABA(A) receptors in motoneurons. By intracellular recordings made with sharp electrodes and the whole-cell patch clamp recording technique we show here that the membrane input resistance and the monosynaptic excitatory post-synaptic potential (EPSPs) are significantly increased by bicuculline. Likewise, the depression of the EPSPs and the input membrane resistance normally induced by muscimol was partially reverted by 20 μM bicuculline and abolished when the concentration of the antagonist was raised to 100 μM. Last, bicuculline at low concentration did not affect the holding current as occur with the high concentration that block the tonic inhibitory GABAergic current. Together these results suggest that the excitability in motoneurons may be tonically inhibited by high affinity GABA(A) receptors.

Microwave Processing Applied to Ceramic Reactions

The necessary energy for processing ceramics usually comes from gas firing or electricity. With gas firing, ceramics processing is conducted at relative low temperatures. In the case of electric arc furnace, temperatures are high enough to smelt the material and the reaction takes place in a liquid state. In this work we use microwave radiation for conducting reactions between oxides to produce ceramic materials, mainly spinels. The microwave energy was supplied using an 800W magnetron operating at 2.45 GHz. The microstructure and the mineral composition were studied by means of SEM and X-Ray diffractometer respectively.

Cortical hyperexcitability in response to preserved spinothalamic inputs immediately after spinal cord hemisection

Chronic injury of the main somatosensory pathways ascending along the spinal cord - the dorsal columns and the spinothalamic tract - can produce both changes in the organization of cortical somatotopic maps and neuropathic pain. Little is known, however, about the early neurophysiological changes occurring immediately after injury. We bilaterally recorded the neural activity of the hindpaw representation of the primary somatosensory cortex evoked by stimuli delivered to the hindpaws before and immediately after a thoracic spinal cord hemisection in anesthetized rats. This unilateral spinal cord injury allowed us to separately investigate the cortical effects of deafferenting the dorsal column (stimuli ipsilateral to the hemisection) or the spinothalamic tract (stimuli contralateral to the hemisection). The hemisection produced immediate bilateral changes in the cortical responses evoked by stimuli delivered to the hindpaw ipsilateral to the hemisection (deafferented dorsal column): an expected loss of classical short-latency cortical responses, accompanied by an unexpected appearance of long-latency activations. At the population level, these activations reflected a progressive stimulus-induced transition of the hindpaw somatosensory cortex from up-and-down states to a sustained activated state. At the single-cell level, these cortical activations resembled the "wind-up" typically observed - with the same type of stimuli - in the dorsal horn cells originating the spinothalamic tract. Virtually no changes were observed in the responses evoked by stimuli delivered to the hindpaw contralateral to the hemisection (deafferented spinothalamic tract). These results suggest that spinal cord hemisection immediately produces an abnormal hyperexcitability of the primary somatosensory cortex in response to preserved spinothalamic inputs from the hindpaw. This immediate cortical hyperexcitability could be important to understand the long-term development of cortical reorganization and neuropathic pain after incomplete spinal cord lesions.

172 PREGNANCY RATES AND EARLY PREGNANCY LOSSES IN POSTPARTUM EQUINE EMBRYO RECIPIENTS

In commercial equine embryo transfer programs, the cost of recipient mares represents one of the major economical items that increases the final cost of the pregnancies (Douglas 1985; Losinno and Alvarenga 2006). Due to the risks to newborn foal, it is uncommon to use foaling recipients in the large equine embryo transfer programs in Argentina. The objective of this study was to evaluate pregnancy and early embryonic loss rates between foaling and non-foaling recipients in a commercial embryo transfer program. A total of 173 embryos were collected from Arabian donor mares during 3 consecutive breeding seasons, 2006-2009. Donor mare’s ages ranged from 2 to 22 years, and donors were inseminated with either fresh or frozen semen from 8 stallions 2-17 years old and of proved fertility. Uterine flushing was performed on Day 8 to 9 post-ovulation by standard techniques (Douglas 1985) and recovered embryos were transferred nonsurgically. Recipient mares 3-12 years old were selected clinically by rectal palpation and ultrasound. All embryos were transferred to synchronized recipient mares (-1 to +1 according to donor’s ovulation day) and randomly assigned to non-foaling (n = 84) or foaling (n = 89) recipient groups. For the analysis, we first considered pregnancy and early pregnancy loss rates in both groups, and second, the foaling mares were divided in 3 groups according to the days between foaling and transfer: 1) before 30 days postpartum (n = 10), 2) between 31 and 60 days postpartum (n = 30), and 3) after 61 days postpartum (n = 49). Pregnancy diagnosis was performed by ultrasonography on Days 14, 30, and 60 post-ovulation of the donor. Results were evaluated by chi-square test. No statistical differences (P > 0.05) were observed in pregnancy rates between non-foaling and foaling recipients (76.2% and 80.9%, respectively) and in post-foaling groups (80% for recipients transferred before 30 days postpartum, 73.3% for recipients transferred between 31 to 60 days postpartum, and 85.7% for recipients transferred after 61 days postpartum). No statistical differences (P > 0.05) were found in pregnancy loss rates between recipients transferred before 30 and after 61 days postpartum (25% v. 4.8%, respectively) and between recipients transferred before 30 days postpartum and the non-foaling group (25% v. 10.9%, respectively). Pregnancy loss rates for recipients transferred after 31 and 61 days postpartum (9.1% and 4.8%, respectively) were not significantly different with the non-foaling group, and both are within previously reported values. Our results show that postpartum recipients can be used 30 days after normal foaling in a commercial embryo transfer program with similar pregnancy and early pregnancy loss rates and can be a valuable tool maximizing the use of the recipient mares during consecutive breeding seasons.

405 LEVELS OF HORMONES AND NITRIC OXIDE PRESENT IN FOLLICULAR FLUID UNDER OR NOT UNDER SUPEROVULATION IN MARES

The aim of the present study was to compare the levels of 17β-estradiol, testosterone, progesterone, inibin, and nitric oxide in follicular fluid between superovulated mares (G1) using equine pituitary extract (EPE) and nonsuperovulated mares (G2) used as control. Two estrus cycles from 24 mares (G1 = 12; G2 = 12) were monitored. In G1, the first cycle was used to determine the ovulation day (Day 0), followed by the administration of PGF2 (250 μg daily of cloprostenol; Sincrocio™, Ouro Fino, São Paulo, Brazil) on the first and second day of treatment with EPE. During the second cycle, EPE (25 mg i.m.) was administered twice daily from Day 7 to the ultrasound detection of a majority of follicles at least 35 mm in diameter. At this time, 2500 IU of hCG IV (Vetecor™, Hertape Calier, Minas Gerais, Brazil) was given. The same protocol was used for G2 as was used for G1 except that EPE administration was replaced by saline injections. For follicular aspiration, the mares were sedated with xilazine (0.5 mg kg-1; Sedazine™, Fort Dodge, São Paulo, Brazil) and acepromazine (0.05 mg kg-1; Acepram 1%™, Univet, Milton, Ontario Canada); hioscin bromide (Buscofin™, Agener União, São Paulo, Brazil) was also administered to reduce intestinal motility and to make ovary manipulation by way of the rectum easier. All follicles larger than 35 mm were aspirated using a Cook® double lumen needle (12 GA) in a transvaginal aspiration probe guided by ultrasonography. The number of aspirated preovulatory follicles was 4.75 ± 2.7 and 1.0 ± 0.0 for G1 and G2, respectively. The follicular fluid collected was centrifuged at 600 × g for 10 min in order to separate the fluid from the cells. The fluid was stored at -20°C and sent to the University of California (Davis, USA) for hormonal assay. The nitric oxide dosage was determined at São Paulo State University (Botucatu, Brazil) using the luminescent reaction of Griess. The comparison between groups of hormonal levels and nitric oxide was performed using the t-test at 5% significance. The results of the present study showed that the EPE treatment (G1), under the experimental conditions, did not lead to a significant change in the mean concentrations of the evaluated hormones or of nitric oxide in the follicular fluid when compared with the levels in G2. However, differences were found among the individuals only in G1 in all hormones (P < 0.05), with exception of progesterone (P > 0.05). Table 1.Mean and standard error of the follicular fluid hormones and nitric oxide levels of groups G1 and G2 Supported by FAPESP, Brazil.

Quality specifications for seminal parameters based on clinicians' opinions

BACKGROUND

The aim of this study was to identify analytical quality specifications for seminal parameters based on clinicians' opinions, and to compare with those based on biological variability and state of the art.

MATERIAL AND METHODS

Two questionnaires with case histories were sent to laboratories participating in the Spanish programme of external quality on semen analysis for distribution to as many specialist clinicians as possible. Our intention was to determine the critical difference (CD), defined as the difference needed between two consecutive results obtained from semen analysis to be 95 % confident that the two results actually are different. Subsequently, we calculated the specifications of analytical quality in accordance with the clinicians' opinions.

RESULTS

The CDs obtained from the median value of the differences between the initial value and that given in the clinicians' replies were similar in clinical situations of improvement or worsening in the infertile normozoospermic male, and also in worsening situations for male patients presenting a significant alteration in seminal parameters. For improvement in this latter case, the CD cited as necessary in the clinicians' opinion was much higher than that for the other clinical situations. At a desirable level of quality, for concentration and total motility the coefficients of variation in the clinicians' opinion were below those based on biological variability and the state of the art. However, for type "a+b" motility, type "a" motility, morphology and vitality the coefficients of variation based on the clinicians' opinions were higher than those based on biological variability and lower than those based on the state of the art.

CONCLUSIONS

Quality specifications for seminal parameters based on clinicians' opinions depend to a large extent on the clinical situation and on the seminal parameter being analysed.

Effect of type of semen, time of insemination relative to ovulation and embryo transfer on early equine embryonic vesicle growth as determined by ultrasound

Embryonic vesicle growth in the mare is easily monitored by ultrasound. Apart from pregnancy diagnosis, assessment of the embryonic vesicle in practice is also useful to evaluate its viability. Although subject to individual variation, embryo growth rate follows a constant pattern in the early stages of development in relation to embryonic age. Previous studies have shown a significant effect of some factors routinely used in practice, such as post-ovulation insemination and embryo transfer, on embryonic growth and the time in which the vesicle is first detected. This study attempts to confirm previous results in different settings and characterise the causes for this delay in growth. A total of 159 pregnancies from different mating protocols: (1) pre-ovulation natural mating, (2) pre-ovulation natural mating and transfer into recipient mares, (3) post-ovulation natural mating, and (4) post-ovulation AI with frozen/thaw spermatozoa were evaluated ultrasonographically from day 12 to 19 of pregnancy and vesicle diameters recorded. Regression analysis between embryonic vesicle diameters and embryonic ages was performed for each group and mean vesicle diameter at different age periods among groups were tested for statistical difference with a general linear model of variance. There was no significant difference between groups 1 and 2 (P=0.73) or between groups 3 and 4 (P=0.71). However both pre-ovulation groups (1 and 2) had larger vesicle diameters (P<0.000) at any embryonic age analysed than either of the post-ovulation groups (3 and 4). In conclusion, post-ovulation inseminations produced pregnancies with smaller vesicle diameters equivalent to approximately 1 day's growth.

Tactile responses of hindpaw, forepaw and whisker neurons in the thalamic ventrobasal complex of anesthetized rats

The majority of studies investigating responses of thalamocortical neurons to tactile stimuli have focused on the whisker representation of the rat thalamus: the ventral–posterior–medial nucleus (VPM). To test whether the basic properties of thalamocortical responses to tactile stimuli could be extended to the entire ventrobasal complex, we recorded single neurons from the whisker, forepaw and hindpaw thalamic representations. We performed a systematic analysis of responses to stereotyped tactile stimuli − 500 ms pulses (i.e. ON–OFF stimuli) or 1 ms pulses (i.e. impulsive stimuli) − under two different anesthetics (pentobarbital or urethane). We obtained the following main results: (i) the tuning of cells to ON vs. OFF stimuli displayed a gradient across neurons, so that two-thirds of cells responded more to ON stimuli and one-third responded more to OFF stimuli; (ii) on average, response magnitudes did not differ between ON and OFF stimuli, whereas latencies of response to OFF stimuli were a few milliseconds longer; (iii) latencies of response to ON and OFF stimuli were highly correlated; (iv) responses to impulsive stimuli and ON stimuli showed a strong correlation, whereas the relationship between the responses to impulsive stimuli and OFF stimuli was subtler; (v) unlike ON responses, OFF responses did not decrease when stimuli were moved from the receptive field center to a close location in the excitatory surround. We obtained the same results for hindpaw, forepaw and whisker neurons. Our results support the view of a neurophysiologically homogeneous ventrobasal complex, in which OFF responses participate in the structure of the spatiotemporal receptive field of thalamocortical neurons for tactile stimuli.