7-Nitroindazole reduces L-DOPA-induced dyskinesias in non-human Parkinsonian primate.

Nitric oxide (NO) plays a pivotal role in integrating dopamine transmission in the basal ganglia and has been implicated in the pathogenesis of Parkinson disease (PD). The objective of this study was to ascertain whether the NO synthase inhibitor, 7-nitroindazole (7-NI), is able to reduce L-DOPA-induced dyskinesias (LIDs) in a non-human primate model of PD chronically intoxicated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Six Parkinsonian macaques were treated daily with L-DOPA for 3-4 months until they developed LIDs. Three animals were then co-treated with a single dose of 7-NI administered 45 min before each L-DOPA treatment. Dyskinetic MPTP-treated monkeys showed a significant decrease in LIDs compared with their scores without 7-NI treatment (p < 0.05). The anti-Parkinsonian effect of L-DOPA was similar in all three monkeys with and without 7-NI co-treatment. This improvement was significant with respect to the intensity and duration of LIDs while the beneficial effect of L-DOPA treatment was maintained and could represent a promising therapy to improve the quality of life of PD patients.

Identification of differentially expressed genes profiles in a combined mouse model of Parkinsonism and colitis.

Different cellular mechanisms have been described as being potentially involved in the progression of neurodegeneration in Parkinson's disease, although their role is still unclear. The present study aimed to identify in detail, through differentially expressed genes analysis by bioinformatics approaches, the molecular mechanisms triggered after a systemic insult in parkinsonian mice. To address this objective, we combined a dextran sodium sulfate (DSS)-induced ulcerative colitis experimental mice model with an acute 1-methyl-4-phenyl-1,2,3,6-tetradropyridine (MPTP) intoxication. The animals were divided into four experimental groups based on the different treatments: (i) control, (ii) DSS, (iii) MPTP and (iv) MPTP + DSS. The data obtained by microarray and functional enrichment analysis point out the implication of different molecular mechanisms depending on the experimental condition. We see, in the striatum of animals intoxicated only with DSS, dysfunction processes related to the blood. On the other hand, oxidative stress processes are more prominent at the MPTP intoxicated mice. Finally, differentially expressed genes within the MPTP + DSS show functional enrichment in inflammation and programmed cell death. Interestingly, we identify a significant synergistic negative effect of both toxins since the expression of differentially expressed genes (DEGs) related to balanced cellular homeostasis was not enough to prevent processes associated with cell death. This work provides detailed insights into the involvement of systemic inflammation, triggered after an insult in the colon, in the progression of the degeneration in Parkinsonism. In this way, we will be able to identify promising therapeutic targets that prevent the contribution of inflammatory processes in the progression of Parkinson's disease.

Electrical stimulation or MK-801 in the inferior colliculus improve motor deficits in MPTP-treated mice.

The inferior colliculus (IC) is an important midbrain relay station for the integration of descending and ascending auditory information. Additionally, the IC has been implicated in processing sensorimotor responses. Glutamatergic and GABAergic manipulations in the IC can improve motor deficits as demonstrated by the animal model of haloperidol-induced catalepsy. However, how the IC influences motor function remains unclear. We investigated the effects of either intracollicular deep brain stimulation (DBS) or microinjection of the glutamatergic antagonist MK-801 or the agonist NMDA in C57BL/6J mice chronically treated with saline or 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). After DBS or microinjections, the mice were submitted to rotarod and open field tests, respectively. DBS in the IC was effective to increase the time spent on the rotarod in MPTP-treated mice. After unilateral microinjection of MK-801, but not NMDA, MPTP-treated mice increased the distance travelled in the open field (p < 0.05). In conclusion, intracollicular DBS or MK-801 microinjection can improve motor performance in parkinsonian mice suggesting the IC as a new and non-conventional therapeutic target in motor impairment.

Transcranial magnetic stimulation and aging: Effects on spatial learning and memory after sleep deprivation in Octodon degus.

The benefits of neuromodulatory procedures as a possible therapeutic application for cognitive rehabilitation have increased with the progress made in non-invasive modes of brain stimulation in aged-related disorders. Transcranial magnetic stimulation (TMS) is a non-invasive method used to examine multiple facets of the human brain and to ameliorate the impairment in cognition caused by Alzheimer's disease (AD). The present study was designed to evaluate how a chronic TMS treatment could improve learning and memory functions after sleep deprivation (SD) in old Octodon degus. SD was executed by gently handling to keep the animals awake throughout the night. Thirty young and twenty-four old O. degus females were divided in six groups (control, acute and chronic TMS treatment). Behavioral tests included; Radial Arm Maze (RAM), Barnes Maze (BM) and Novel Object Recognition (NOR). Although learning and memory functions improved in young animals with only one session of TMS treatment, a significant improvement in cognitive performance was seen in old animals after 4 and 7days of TMS, depending on the task that was performed. No side effects were observed following, which showed therapeutic potential for improving age-related cognitive performance.

Cognitive Impairment After Sleep Deprivation Rescued by Transcranial Magnetic Stimulation Application in Octodon degus.

Sleep is indispensable for maintaining regular daily life activities and is of fundamental physiological importance for cognitive performance. Sleep deprivation (SD) may affect learning capacity and the ability to form new memories, particularly with regard to hippocampus-dependent tasks. Transcranial magnetic stimulation (TMS) is a non-invasive procedure of electromagnetic induction that generates electric currents, activating nearby nerve cells in the stimulated cortical area. Several studies have looked into the potential therapeutic use of TMS. The present study was designed to evaluate how TMS could improve learning and memory functions following SD in Octodon degus. Thirty juvenile (18 months old) females were divided into three groups (control, acute, and chronic TMS treatment-with and without SD). TMS-treated groups were placed in plastic cylindrical cages designed to keep them immobile, while receiving head magnetic stimulation. SD was achieved by gently handling the animals to keep them awake during the night. Behavioral tests included radial arm maze (RAM), Barnes maze (BM), and novel object recognition. When TMS treatment was applied over several days, there was significant improvement of cognitive performance after SD, with no side effects. A single TMS session reduced the number of errors for the RAM test and improved latency and reduced errors for the BM test, which both evaluate spatial memory. Moreover, chronic TMS treatment brings about a significant improvement in both spatial and working memories.

Effects of surgery and/or remifentanil administration on the expression of pERK1/2, c-Fos and dynorphin in the dorsal root ganglia in mice.

Tissue injury and/or opioids induce plastic changes in the spinal cord resulting in pain hypersensitivity; the contribution of the dorsal root ganglia (DRG) is poorly understood. We evaluated DRG phenotypic changes induced by surgery and/or remifentanil in a mice model of postoperative pain using as neuronal markers ERK1/2 and c-Fos; prodynorphin mRNA and dynorphin levels were also determined. We hypothesized that a correlation between nociception and DRG reactivity would occur. Surgery and/or remifentanil induced mechanical hypersensitivity, correlated with ERK1/2 phosphorylation and c-Fos expression in the DRG; changes were greater in the remifentanil + incision group and still present on day 14 (p < 0.01 vs. control). Intrathecal PD98059 (ERK1/2 inhibitor) partially reversed the mechanical hypersensitivity (44%, p < 0.05) observed in the remifentanil + incision group. In this group, significant increases in prodynorphin mRNA (at 2, 7, and 14 days, p < 0.01) roughly coincided with increases in dynorphin (days 2 and 14, p < 0.001) in the DRG. Remifentanil or incision (alone) also induced an up-regulation in prodynorphin mRNA expression on days 7 and 14 (p < 0.01, p < 0.05, respectively), partially correlating with dynorphin levels. On day 21, all molecular changes returned to control levels in all experimental conditions, concurring with the complete recovery of nociceptive thresholds. Surgery and/or remifentanil induce up-regulation of c-Fos and pERK in the DRG, approximately correlating with nociceptive behavior, also associated with an increased expression of prodynorphin/dynorphin. These changes support the role of the DRG in the development and maintenance of pain hypersensitivity after surgery. The findings could contribute to the development of new therapeutic agents focused on peripheral targets.

Enhanced tyrosine hydroxylase phosphorylation in the nucleus accumbens and nucleus tractus solitarius-A2 cell group after morphine-conditioned place preference.

Although dopamine (DA) has been extensively implicated in the morphine-induced conditioned place preference (CPP; a measure of reward), noradrenaline (NA) and other systems may play a larger role than previously suspected. The mesolimbic DA system, comprised of projections from the ventral tegmental area (VTA) to the nucleus accumbens (NAc), receives noradrenergic innervations from the nucleus tractus solitaries (NTS)-A2 cell group and is modulated by NA. The purpose of the present study was to evaluate the turnover of DA and NA in the NAc and the site-specific phosphorylation of TH in the NAc, VTA, and NTS on the CPP mice conditioned by morphine. A dose-effect curve for morphine-induced CPP (0.5-8 mg/kg, s.c.) was obtained using 6-day conditioning sessions followed by a CPP test. TH phosphorylation was determined by quantitative blot immunolabeling and immunohistochemistry using phosphorylation state-specific antibodies; NA and DA turnover was evaluated by high-performance liquid chromatography. Morphine-induced CPP phosphorylates TH at serine (Ser)40 but not Ser31 in NAc, which is associated with an enhanced of DA and NA turnover. We also found that morphine-induced CPP increased levels of TH phosphorylated at Ser31 and Ser40 in the NTS. The present study demonstrates that morphine-induced CPP might stimulate TH activity and accelerate DA and NA turnover in the NAc via a mechanism involving phosphorylation of TH.

Differential involvement of 3', 5'-cyclic adenosine monophosphate-dependent protein kinase in regulation of Fos and tyrosine hydroxylase expression in the heart after naloxone induced morphine withdrawal.

We previously demonstrated that morphine withdrawal induced hyperactivity of the heart by the activation of noradrenergic pathways innervating the left and right ventricle, as evaluated by noradrenaline (NA) turnover and Fos expression. We investigated whether cAMP-dependent protein kinase (PKA) plays a role in this process by estimating changes in PKA immunoreactivity and the influence of inhibitor of PKA on Fos protein expression, tyrosine hydroxylase (TH) immunoreactivity levels and NA turnover in the left and right ventricle. Dependence on morphine was induced by a 7-day s.c. implantation of morphine pellets. Morphine withdrawal was precipitated on day 8 by an injection of naloxone (5 mg/kg). When opioid withdrawal was precipitated, an increase in PKA immunoreactivity and phospho-CREB (cyclic AMP response element protein) levels were observed in the heart. Moreover, morphine withdrawal induces Fos expression, an enhancement of NA turnover and an increase in the total TH levels. When the selective PKA inhibitor HA-1004 was infused, concomitantly with morphine pellets, it diminished the increase in NA turnover and the total TH levels observed in morphine-withdrawn rats. However, this inhibitor neither modifies the morphine withdrawal induced Fos expression nor the increase of nonphosphorylated TH levels. The present findings indicate that an up-regulated PKA-dependent transduction pathway might contribute to the activation of the cardiac catecholaminergic neurons in response to morphine withdrawal and suggest that Fos is not a target of PKA at heart levels.

Evidence for a peripheral mechanism in cardiac opioid withdrawal.

Studies involving heart catecholaminergic systems in morphine-dependent rats have not established whether the adaptive changes observed in the heart during morphine withdrawal are mediated peripherally or centrally. In this study, naloxone (Nx), naloxone methiodide (NxM) and N-methyl levallorphan (NML), quaternary derivatives of Nx and levallorphan, respectively, that do not cross the blood-brain barrier, were administered to morphine-dependent rats and catecholamines and their metabolites determined in the right ventricle. Rats were made dependent on morphine by implantation of morphine pellets for 7 days. On day 8 animals received s.c. injections of saline, Nx (1 mg/kg), NxM (5 mg/kg) or NML (5 mg/kg) and were decapitated 30 min later. Noradrenaline (NA) and its metabolites normetanephrine (NMN) and 3-methoxy-4-hydroxyphenylethyleneglycol (MHPG) and dopamine (DA) and its metabolite 3,4-dihydroxyphenylacetic acid (DOPAC) were determined by high-performance liquid chromatography with electrochemical detection. After NxM or NML administration to morphine-dependent rats there was a pronounced increase in NMN and DOPAC levels, as well as in NA and DA turnovers (as estimated by NMN/NA and DOPAC/DA ratios, respectively) in the right ventricle. Similarly, giving Nx to morphine-dependent rats increased NMN and DOPAC levels and NA and DA turnovers. In addition, in the paraventricular nucleus of the hypothalamus (PVN) NA and DA turnover, measured as the MHPG/NA or DOPAC/DA ratios, increased after Nx administration but not after NxM or NML These results suggest that the changes in cardiac sympathetic activity observed during morphine withdrawal are due to intrinsic mechanisms outside the central nervous system. These data may be important for understanding the adaptive changes induced in the heart in subjects dependent on opioids.

Changes in catecholaminergic pathways innervating paraventricular nucleus and pituitary-adrenal axis response during morphine dependence: implication of alpha(1)- and alpha(2)-adrenoceptors.

We have previously shown an enhanced activity of the pituitary-adrenal response in rats dependent on morphine, which occurs concomitantly with an increase in the activity of catecholaminergic terminals in the hypothalamic paraventricular nucleus (PVN). The present study examined the possible role of noradrenergic system in the regulation of opioid withdrawal-induced activation of the hypothalamus-pituitary-adrenocortical (HPA) axis activity. Rats were given morphine by s.c. implantation of morphine pellets for 7 days. On the seventh day, morphine withdrawal was induced by s.c. administration of naloxone (1 mg/kg), rats were sacrificed 30 min later, and changes in noradrenaline (NA) turnover (estimated by the 3-methoxy-4-hydroxyphenylethylen glycol/NA ratio) and in dopamine turnover (estimated by the 3,4-dihydroxyphenylacetic acid/dopamine ratio) in the PVN (HPLC with electrochemical detection) and in plasma corticosterone levels were determined. We found a parallelism between the behavioral signs of withdrawal, an increased activity of noradrenergic and dopaminergic terminals in the PVN, and the hypersecretion of the HPA axis. Pretreatment with alpha(1)- or alpha(2)-adrenoceptor antagonists prazosin or yohimbine, respectively, 15 min before naloxone administration significantly prevented the withdrawal-induced corticosterone hypersecretion and attenuated the behavioral signs of morphine withdrawal. In addition, biochemical analysis indicated that both prazosin and yohimbine completely abolished the withdrawal-induced increase in NA turnover in the PVN. In contrast, neither prazosin nor yohimbine modified the hyperactivity of dopaminergic terminals in the PVN during withdrawal. Collectively, these data suggest that the secretory activity in the HPA axis after morphine withdrawal results from an increase in noradrenergic activity that is dependent on alpha(1)- and alpha(2)-adrenoceptor activation. Activation of dopaminergic pathways might not contribute to the neuroendocrine response during withdrawal.