João Eduardo de Araujo

Anxiogenic effects of substance P and its 7–11 C terminal, but not the 1–7 N terminal, injected into the dorsal periaqueductal gray☆☆

The dorsal periaqueductal gray matter (DPAG) is one of the main output regions of the brainstem for the expression of defense reaction. Recent findings implicating neurokinins in the expression of fear or anxiety-like behaviors, have stimulated interest in the participation of these neuropeptides in the generation of aversive states in the dorsal periaqueductal gray matter. Analyses of traditional measures of the behavior of rats submitted to the elevated plus-maze test in this laboratory have shown that microinjections of substance P (SP) into the DPAG produce anxiogenic-like effects. The present study employs an ethological analysis of the behavior of animals in this test to investigate the involvement of substance P (SP) and its C- and N- fragments (7-11 and 1-7) in the expression of the different aspects of fear upon injection into the DPAG. To this end, rats were implanted with a cannula in the DPAG and injected one week later with 35 and 70 pmol of either substance P, or C- or N- SP fragments and tested immediately afterwards in the elevated plus-maze. The results show that SP and its C terminal fragment, produced increases in scanning, stretched attend posture, head dipping and flat-back approach, whereas the fragment N terminal produced only an increase in rearing. Therefore, the effects of SP and its C terminal fragment were associated to risk assessment behavior, whereas those of N terminal fragment were related to vertical exploratory activity. The results indicate that SP produces anxiogenic effects through activation of neural substrates of aversion in the DPAG and that this effect is probably related to its C terminal fragment.

Nitric oxide synthesis blockade reduced the baroreflex sensitivity in trained rats.

OBJECTIVE The present study has investigated the effect of blockade of nitric oxide synthesis on cardiovascular autonomic adaptations induced by aerobic physical training using different approaches: 1) double blockade with methylatropine and propranolol; 2) systolic arterial pressure (SAP) and heart rate variability (HRV) by means of spectral analysis; and 3) baroreflex sensitivity. METHODS Male Wistar rats were divided into four groups: sedentary rats (SR); sedentary rats treated with N(omega)-nitro-l-arginine methyl ester (L-NAME) for one week (SRL); rats trained for eight weeks (TR); and rats trained for eight weeks and treated with L-NAME in the last week (TRL). RESULTS Hypertension and tachycardia were observed in SRL group. Previous physical training attenuated the hypertension in L-NAME-treated rats. Bradycardia was seen in TR and TRL groups, although such a condition was more prominent in the latter. All trained rats had lower intrinsic heart rates. Pharmacological evaluation of cardiac autonomic tonus showed sympathetic predominance in SRL group, differently than other groups. Spectral analysis of HRV showed smaller low frequency oscillations (LF: 0.2-0.75 Hz) in SRL group compared to other groups. Rats treated with L-NAME presented greater LF oscillations in the SAP compared to non-treated rats, but oscillations were found to be smaller in TRL group. Nitric oxide synthesis inhibition with L-NAME reduced the baroreflex sensitivity in sedentary and trained animals. CONCLUSION Our results showed that nitric oxide synthesis blockade impaired the cardiovascular autonomic adaptations induced by previous aerobic physical training in rats that might be, at least in part, ascribed to a decreased baroreflex sensitivity.

Aversive effects of the C-fragment of Substance P in the dorsal periaqueductal gray matter.

Abstract There has been an increasing interest in the role of neuropeptides in the integration of brain functions. Besides the well-known positive-reinforcing effects of Substance P (SP) in prosencephalic regions, a role of this neuropeptide in the generation of aversive states in mesencephalic structures has also been envisaged. Evidence from a previous study suggests an involvement of SP in the neural substrates of aversion in the dorsal periaqueductal gray matter (DPAG). In the present study, we investigate whether N- and C-terminal fragments of Substance P are responsible for the effects produced by microinjections of SP into the dorsal periaqueductal gray. The results show that SP and its C-terminal fragment SP7–11 produced a behavioral activation with increases in locomotor activity, grooming, and rearings, while the N-terminal fragment SP1–7 produced only an increase in vertical exploratory activity. The effects were more pronounced with intermediate doses of SP and its C-fragment, confirming the characteristic bell-shaped dose-effect function of this neuropeptide. The proaversive effects observed with DPAG microinjections of these neuropeptides in the present study gain further relevance when combined with previous reports showing unconditioned and conditioned aversive effects following DPAG microinjections of SP in the place aversion and the elevated plus maze tests, two widely used animal models of anxiety. These results confirm previous data showing that SP has a modulatory role in the DPAG and that its effects are probably due to its C-terminal fragment.

Opposite effects of substance P fragments C (anxiogenic) and N (anxiolytic) injected into dorsal periaqueductal gray

Recent findings implicating neurokinins in the expression of anxiety-like behaviors have stimulated interest in the participation of these neuropeptides in the dorsal periaqueductal gray matter (dPAG), one of the main output regions of the brainstem for the expression of defense reaction. Studies on the behavior of rats submitted to the elevated plus-maze test in this laboratory have shown that microinjections of substance P into the dorsal periaqueductal gray produce anxiogenic-like effects. Now, we analyze what portion of the molecule of substance P is responsible for these effects through the examination of the action of its C- and N-terminus fragments (6-11 and 1-7) in the elevated plus-maze. We also investigated whether these effects are influenced by prior treatment with the tachykinin NK(1) receptor antagonist 17-beta-hydroxy-17-alpha-ethynyl-5alpha-androstanol[3,2-b]pyrimido[1,2-a]benzimidazole (WIN51,708). To this end, rats were implanted with a cannula in the dorsal periaqueductal gray and injected 1 week later with equimolar doses (17.5 and 35 pmol) of either C- or N-fragments of substance P and tested in the elevated plus-maze. The results show that the C-terminal fragment has an anxiogenic profile of effects, including reduction in the number of entries and time spent in the open arms of the maze, plus increases in scanning, stretched-attend posture, head dipping and flat-back approach. On the other hand, the N-terminal fragment produced opposite effects, namely, an increase in the number of entries and time spent in the open arms of the maze accompanied by an increase in end-arm activity, rearing and head dipping. The tachykinin NK(1) receptor antagonist WIN51,708 (20 mg/kg, i.p.) inhibited the effects of the carboxy-terminal of substance P while it did not change the effects of the N-terminal fragment. Microinjection of WIN51,708 (20 mg/kg, i.p.), by its own, did not produce any significant effects. Therefore, the results indicate that the anxiogenic effects of substance P injected into the dorsal periaqueductal gray are encoded by its carboxy-terminal sequence and due to its action on tachykinin NK(1) receptors.

The immediate effects of local and adjacent acupuncture on the tibialis anterior muscle: a human study

BackgroundThis study compares the immediate effects of local and adjacent acupuncture on the tibialis anterior muscle and the amount of force generated or strength in Kilogram Force (KGF) evaluated by a surface electromyography.MethodsThe study consisted of a single blinded trial of 30 subjects assigned to two groups: local acupoint (ST36) and adjacent acupoint (SP9). Bipolar surface electrodes were placed on the tibialis anterior muscle, while a force transducer was attached to the foot of the subject and to the floor. An electromyograph (EMG) connected to a computer registered the KGF and root mean square (RMS) before and after acupuncture at maximum isometric contraction. The RMS values and surface electrodes were analyzed with Students t-test.ResultsThirty subjects were selected from a total of 56 volunteers according to specific inclusion and exclusion criteria and were assigned to one of the two groups for acupuncture. A significant decrease in the RMS values was observed in both ST36 (t = -3.80, P = 0,001) and SP9 (t = 6.24, P = 0.001) groups after acupuncture. There was a decrease in force in the ST36 group after acupuncture (t = -2.98, P = 0.006). The RMS values did not have a significant difference (t = 0.36, P = 0.71); however, there was a significant decrease in strength after acupuncture in the ST36 group compared to the SP9 group (t = 2.51, P = 0.01). No adverse events were found.ConclusionAcupuncture at the local acupoint ST36 or adjacent acupoints SP9 reduced the tibialis anterior electromyography muscle activity. However, acupuncture at SP9 did not decrease muscle strength while acupuncture at ST36 did.

Place aversion induced by microinjections of C-fragment of substance P into the dorsal periaqueductal gray of rats is mediated by tachykinin NK1 receptors

Neural circuits in the dorsal periaqueductal gray matter (dPAG) play an important role in the integration of defensive behavior. The neurokinin substance P causes conditioned place aversion when administered into this region. The present study examined whether these effects may be mimicked by its carboxy-terminal amino acid sequence and whether they are influenced by prior treatment with the tachykinin NK1 receptor antagonist WIN51,708. The behavioral testing apparatus is a circular open field consisting of 4 uniform quadrants that are equally preferred by the rats prior to drug treatments. For conditioning, rats received drug injections on three consecutive days and were placed into their assigned quadrant. The carboxy-terminal analog (17.5 pmol/0.2 microl) applied into the dPAG produced place aversion effects with reduced time spent in the drug-paired quadrant on the testing day. The effects of the carboxy-terminal analog was antagonized by pretreatment with WIN51,708 (20 mg/kg, i.p.). Microinjection of WIN51,708 (20 mg/kg, i.p.), by its own, did not produce significant effects. These findings suggest that previous reports showing conditioned place aversion effects of SP injected into the dPAG are encoded by its carboxy-terminal sequence and due to its action on tachykinin NK1 receptors.

Modified constraint-induced movement therapy and modified forced-use therapy for stroke patients are both effective to promote balance and gait improvements

BACKGROUND Previous studies show that chronic hemiparetic patients after stroke, presents inabilities to perform movements in paretic hemibody. This inability is induced by positive reinforcement of unsuccessful attempts, a concept called learned non-use. Forced use therapy (FUT) and constraint induced movement therapy (CIMT) were developed with the goal of reversing the learned non-use. These approaches have been proposed for the rehabilitation of the paretic upper limb (PUL). It is unknown what would be the possible effects of these approaches in the rehabilitation of gait and balance. OBJECTIVES To evaluate the effect of Modified FUT (mFUT) and Modified CIMT (mCIMT) on the gait and balance during four weeks of treatment and 3 months follow-up. METHODS This study included thirty-seven hemiparetic post-stroke subjects that were randomly allocated into two groups based on the treatment protocol. The non-paretic UL was immobilized for a period of 23 hours per day, five days a week. Participants were evaluated at Baseline, 1st, 2nd, 3rd and 4th weeks, and three months after randomization. For the evaluation we used: The Stroke Impact Scale (SIS), Berg Balance Scale (BBS) and Fugl-Meyer Motor Assessment (FM). Gait was analyzed by the 10-meter walk test (T10) and Timed Up & Go test (TUG). RESULTS Both groups revealed a better health status (SIS), better balance, better use of lower limb (BBS and FM) and greater speed in gait (T10 and TUG), during the weeks of treatment and months of follow-up, compared to the baseline. CONCLUSION The results show mFUT and mCIMT are effective in the rehabilitation of balance and gait.

Neuropathology and behavioral impairments after three types of global ischemia surgery in Meriones unguiculatus: Evidence in motor cortex, hippocampal CA1 region and the neostriatum

The effects of three types of global ischemia by occlusion of carotid artery on motor and exploratory behaviors of Gerbils were evaluated by the Activity Cage and Rota rod tests. Animals were divided based on two surgical criteria: unilateral (UNI) or bilateral (BIL) carotid occlusion, with (REP) or without (OCL) reperfusion; and their behavior was evaluated on the fourth (4) or sixth (6) day. There was reduction of cell number in striatum, motor cortex M1 area, and hippocampal CA1 area in all groups in comparison to control animals. For M1 area and striatum, the largest reduction was observed in UNI6, UNI4, and BIL4 groups. Neuronal loss was also observed in CA1 area of BIL4 rodents. There was a decrease in crossings and rearings in all groups in activity cage test, compared to control. Reperfusion, unilateral and bilateral occlusion groups showed decrease in crossings. Only the BIL4 showed a decrease of rearing. In the Rota rod test, except the UNIOCL6, the groups showed a decrease in the balance in comparison to control. Both groups with REP4 showed a major decrease in balance. These findings suggest that both unilateral and bilateral carotid occlusions with reperfusion produce impairments of motor and exploratory behavior.

Influence of treadmill training on motor performance and organization of exploratory behavior in Meriones unguiculatus with unilateral ischemic stroke: histological correlates in hippocampal CA1 region and the neostriatum.

This study examined the effects of motor stimulation via treadmill on the behavior of male gerbils after external carotid ischemic brain lesion. The animals were assigned to five groups; ischemic with no stimulation (SIG), ischemic with stimulation (SIG 12/24/48/72h after surgery), non-ischemic with no stimulation (CC), non-ischemic with stimulation (CE) and sham, surgery without occlusion with no stimulation (SH). All the animals were tested in the open-field (OF) and rotarod (RR), 4 days after surgery in order to evaluate exploratory behaviors and motor performance. Data were submitted to one-way variance (ANOVA) and Dunnetts post hoc comparisons. SIG and SIG 12 groups showed a significant decrease in motor response (crossing) when compared to the control group (CC) (F=20.65, P<0.05) in the OF. SIG 12 group showed an increase in grooming behavior (F=23.136, P<0.05) and all ischemia groups (SIG, SIG12/24/48/72) spent less time on the RR (F=10.40, P<0.05), when compared to the control group (CC). Histological analyses show extensive lesions in the hippocampus and neostriatum for all groups with ischemia (SIG, SIG12/24/48/72), which are structures involved in the organization of motor behavior. Interestingly, the most pronounced damage was found in animals submitted to motor stimulation 12h after ischemia which can be correlated to the increased number of grooming behavior showed by them in the OF. These findings suggest that motor stimulation through treadmill training improve motor behavior after ischemia, except when it starts 12h after surgery.

Neuropathology and behavioral impairments after bilateral global ischemia surgery and exposure to static magnetic field: Evidence in the motor cortex, the hippocampal CA1 region and the neostriatum

Abstract Purpose: To evaluate the effects of continuous magnetic field stimulation after four days of global encephalic ischemia on motor behavior and brain morphology in gerbils. Material and methods: Sixty Mongolian gerbils were divided into five groups: Control (CG), sham (SG), ischemia (IG), ischemia north (INPG) and south (ISPG) pole. Experimental animals underwent bilateral occlusion of the carotid artery. In groups with magnetic stimulation, a 3200 gauss magnet was fixed to the skull. After brain perfusion, coronal sections of the striatum, motor cortex (M1) and CA1 area of the hippocampus (CA1) were cut and stained with hematoxylin and eosin. Results: In the open field test (OF) we observed an increase in crossing in the IG compared to the CG, INPG and ISPG (F = 20.19), and a reduction in the time spent on the Rota-rod test (RR) with the IG compared to CG, IPNG and ISPG (F = 17.59). Morphometric analysis revealed a reduction in the density of the neurons in the CA1, in the number of M1 and striatal neurons in the IG compared to the CG, INPG and ISPG. Conclusion: Our results demonstrate a potential therapeutic application of static magnetic fields for the preservation of motor behavior and neurons in regions analyzed after global cerebral ischemia.