Involvement of the glutamatergic system in the nociception induced intrathecally for a TRPA1 agonist in rats.

The transient receptor potential ankyrin 1 (TRPA1) is expressed in peripheral and spinal terminals of sensory neurons, jointly to the vanilloid receptor (TRPV1). A relevant peripheral role of TRPA1 receptor has been implicated in a variety of processes, including the detection of noxious cold, and diverse painful stimulus, but the functional role of TRPA1 receptor in nociceptive transmission at spinal cord in vivo is poorly known. Therefore, the aim of this study was to evaluate whether the glutamatergic system is involved in the transmission of nociceptive stimulus induced for a TRPA1 agonist in the rat spinal cord. We observed that cinnamaldehyde, a TRPA1 agonist, on spinal cord synaptosomes leads to an increase in [Ca(2+)](i) and a rapid release of glutamate, but was not able to change the specific [(3)H]-glutamate binding. In addition, spinally administered cinnamaldehyde produced heat hyperalgesia and mechanical allodynia in rats. This behavior was reduced by the co-injection (i.t.) of camphor (TRPA1 antagonist) or MK-801 (N-methyl-D-aspartate (NMDA) receptor antagonist) to cinnamaldehyde. Besides, the pretreatment with resiniferatoxin (RTX), a potent TRPV1 agonist, abolished the cinnamaldehyde-induced heat hyperalgesia. Here, we showed that intrathecal RTX results in a decrease in TRPA1 and TRPV1 immunoreactivity in dorsal root ganglion. Collectively, our results demonstrate the pertinent participation of spinal TRPA1 in the possible enhancement of glutamatergic transmission of nociceptive signals leading to increase of the hypersensitivity, here observed as heat hyperalgesia. Then the modulation of spinal TRPA1 might be a valuable target in painful conditions associated with central pain hypersensitivity.

Beneficial effects of an innovative exercise model on motor and oxidative disorders induced by haloperidol in rats.

Here we evaluate the influence of a new exercise protocol on movement disorders induced by neuroleptic drugs. In this animal model, involuntary movements are closely related to neuronal degeneration and oxidative stress (OS) that can be caused by pre-synaptic D2 receptor blockade increasing dopamine (DA) metabolism. The increase in vacuous chewing movements (VCM) and the reduced locomotor activity induced by haloperidol treatment (12 mg/kg-im, once a week for 4 weeks) was prevented by exercise, 5 times per week, which was initiated four weeks before the first haloperidol administration. Exercise training also prevented the increase of haloperidol-induced lipid peroxidation in the cortex and subcortical region and recovered the catalase activity in the subcortical region. There was a negative correlation between catalase activity in the subcortical region and the VCM frequency (r = 0.50, p < 0.05), as well as a positive correlation between VCM frequency and lipid peroxidation in the cortex (r = 0.64, p < 0.05) and subcortical region (r = 0.71, p < 0.0001). Both haloperidol and exercise increased DA uptake in the striatum, while the co-treatment (exercise plus haloperidol) reduced it. The striatal DA uptake correlated negatively with catalase activity (r = 0.51, p < 0.05), indicating a relationship between oxidative damage and the function of the transporter in the striatum. Our findings show that physical exercise can modulate dopamine uptake, especially when it is altered, and reveal the benefit of this new exercise protocol in the prevention of movement disorders related to oxidative damage.

Potentially adverse interactions between haloperidol and valerian.

This study was designed to determine whether the treatment with haloperidol (HP), valerian or both in association impairs the liver or kidney functions. Valerian alone did not affect oxidative stress parameters in the liver or kidney of rats. HP alone only increased glutathione (GSH) depletion in liver, but not in kidney. However, when HP was associated with valerian, an increase in lipid peroxidation levels and dichlorofluorescein (DCFH) reactive species production was observed in the hepatic tissue. Superoxide dismutase (SOD) and Catalase (CAT) activities were not affected by the HP plus valerian treatment in the liver and kidney of rats. HP and valerian when administered independently did not affect the activity of hepatic and renal delta-aminolevulinate dehydratase (delta-ALA-D), however, these drugs administered concomitantly provoked an inhibition of hepatic delta-ALA-D activity. The delta-ALA-D reactivation index was higher in rats treated with HP plus valerian than other treated groups. These results strengthen the view that delta-ALA-D can be considered a marker for oxidative stress. Serum aspartate aminotransferase (AST) activity was not altered by any treatment. However, serum alanine aminotransferase (ALT) activity was higher in the HP group and HP plus valerian group. Our findings suggest adverse interactions between haloperidol and valerian.