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Showing 16 results for Electrical Stimulation

Volume 1, Issue 1 (4-1997)

On most adrenergic and cholinergic nerve terminals, prejunctional α-adrenoceptors belonging to the α2-subtype have been identified. Activation of these receptors will decrease the release of norepinephrine. It has been reported that several isolated tissue preparations contain prejunctional dopamine receptors, the stimulation of which inhibits neurotransmission. It has remained uncertain whether the inhibition of cholinergic transmission in the smooth muscle of different tissues is mediated by prejunctional α-adrenoceptors or prejunctional dopaminoceptors. On the basis of these findings we aimed to examine the effects of dopamine and α-adrenergic receptor agonists on twitch response evoked by electrical stimulation of guinea pig common bile duct (CBD). Effects of various doses of bromocriptine and apomorphine, dopamine receptor agonists, on electrically evoked contractile responses of guinea pig CBD were investigated in this study. Bromocriptine and apomorphine produced a concentration -dependent reduction of the twitch heights. IC50 values for bromocriptine and apomorphine were 2.75 ± 0.715 x 10-6 M and 1.69 ± 0.l1 x 10-5 M, respectively. Pretreatment with sulpride, 0.1 and 1.0 µM prevented bromocriptine and apomorphine induced inhibition. PA2 values of sulpiride against bromocriptine and apomorphine were 8.26 and 6.29, respectively. Clonidine, 0.1 -100 µM, produced 49.3 ± 2.5% inhibition of twitch responses. Its effect was partially antagonized by yohimbine (l µM). It is concluded that both dopamine D2 and adrenergic α2 prejunctional receptors are present on the guinea-pig CBD cholinergic nerve and it seems that the role of dopamine D2-receptors is dominant. D2-dopaminoreceptor and α2-adrenoceptor agonists may relieve the biliary spasm.

Volume 2, Issue 1 (4-1998)

  The paragigantocellularis (PGi) nucleus constitutes a large portion of the ventral pontomedullary reticular formation. Neurons within the PGi have been implicated in a variety of functions including cardiovascular regulation, respiratory control, pain and analgesia. Investigators have demonstrated that electrical stimulation and microinjection of L-glutamate into the PGi produce antinociception in phasic pain. In this study, we measured the analgesic effects of electrical stimulation and glutamate microinjection into the PGi using the formalin test and the tail-flick method in rats. A bipolar stimulation electrode and a guide cannula were stereotaxically inserted into the right PGi of individual rats under brief ketamine and xylazine anesthesia. One week after the implantation, a monophasic square wave (500 µs, 400 µA, 50 Hz) was delivered into the PGi for 20 seconds via the implanted electrode. Glutamate (0.5 µl, 44 nM/rat) was injected through the guide cannula. One minute after electrical stimulation or glutamate injection, the tail-flick and formalin (50 ml, 2.5%) tests were performed. The results showed that electrical stimulation and glutamate injection into the PGi caused marked antinociception in both the tail-flick and the early phase of the formalin test compared to the control rats. We conclude that electrical stimulation and glutamate injection into the PGi cause marked antinociception in phasic pain and moderate antinociception in tonic pain. These findings suggest that the PGi is also involved in alleviation of tonic pain.

Masoumeh Sabetkasai, Fatemeh Massodnia, Mohammad Reza Zarrindast,
Volume 2, Issue 1 (4-1998)

  Nomifensine, an antidepressant agent, competitively inhibits dopamine uptake in the caudate-putamen and nucleus accumbens and binds to both dopaminergic and noradrenergic reuptake sites in the striatum and thalamus. In this study the effect of nomifensine on anacoccygeus contraction induced by noradrenaline and electrical stimulation was investigated in rats and compared to the effect of phentolamine, an α-adrenoceptor antagonist. Nomifensine and phentolamine produced a concentration-dependent reduction in the twitch heights. IC50 values for noradrenaline were 2.7 ± 0.02 x 10-7 M in the absence and 2.04 ± 0.027 x 10-6 M in the presence of nomifensine (3 µM/ml), and 3.4 ± 0.03 x 10-6 M in the presence of phentolamine (0.1 µM/ml). We may conclude that nomifensine has α-adrenergic blocker activity similar to phentolamine.

Volume 2, Issue 2 (11-1998)

  It has been shown that acute inflammation reduces the effectiveness of sympathetic nerves in the regulation of knee joint blood flow. To investigate the role of vascular β- adrenoceptors in this event, 12 NZW rabbits were maintained anaesthetized by 1 % halothane in N2O/O2, and acute knee joint inflammation was induced by intra-articular injection of 1 ml of 2% carageenan solution 24 hours before the experiment. On the day of the experiment, a cannula was surgically inserted into the carotid artery to record blood pressure. The medial head of the biceps femoris muscle was removed to provide access to the posterior capsule of the knee and blood flow was measured using a laser flowmeter. Drugs were administered to the joint through a cannula in a branch of the tibial artery. The posterior articular nerve of the knee was also exposed so that it could be electrically stimulated. Electrical stimulation of the posterior articular nerve resulted in a 14.1 ± 3.2% reduction in blood flow measured by laser Doppler flowmetry. This response was reversed to vasodilatation by phentolamine (6.7 ± 1.8%), suggesting the presence of both α and β-adrenoceptors. The vasodilatation response was blocked by propanolol (α β-antagonist) and reduced to about 50% by atenolol (α β1 -antagonist). Also, close intra-arterial injection of different doses of β-agonists increased the joint blood flow by a potency rank order of isoprenaline (β)>dobutamine (β1)>salbutamol (β2). These effects were reduced or blocked by β-antagonists with a potency rank order of propanolol>atenolol. Overall, this study showed a balance between β-adrenoceptor subtypes in the inflamed joint. Compared to our previous investigation on the normal rabbit knee joint in which β1-adrenoceptors were shown to be predominant, acute inflammation caused a shift of β1 towards β2 in the adrenoceptor profile. The clinical significance of this change is not clear at the present time.

Jila Behzadi, Vahid Sheibani, Hossein Esteky, Farzaneh Ganji,
Volume 6, Issue 1 (4-2002)

Behavioral and electrophysiological evidences have shown that locus ceruleus (LC) is involved in different tasks including modulation of sensory processing and shift of attention. In the present study, single unit responses of barrel cortical cells was recorded following controlled mechanical displacement of the principal and peripheral vibrissae in adult rats (100 trials of 200 µm deflection for 10 ms at 1/1.5 second). Mechanical displacement was performed alone and 50 ms after electrical stimulation (10 pulses, 300 µs, 30 µA, 40 Hz) of LC. The onset of evoked responses was defined as the time when spontaneous activity exceeded its mean by two standard deviations. Then, analysis of response latency and response magnitude for periods of 10 and 50 ms following the initiation of evoked response was performed. Response magnitude to principal vibrissae deflection in a period of 10 ms decreased significantly after LC phasic stimulation (p<0.01), but there was no significant difference for a period of 50 ms. In addition, for both time periods, there was no significant differences for response magnitude to peripheral vibrissae deflection before and after LC phasic stimulation. Response latency to principal vibrissae deflection increased significantly after LC stimulation, but it decreased significantly when peripheral vibrissae were deflected (p<0.05). These results support the idea that LC phasic activation has an important role in cortical somatosensory information processing through modulating the receptive field characteristics of cortical neurons.
Arezoo Navid, Giti Torkamani, Seyed Mohammad Firoozabadi,
Volume 7, Issue 2 (10-2003)

Electrical stimulation of neuromuscular system has been used in a variety of research and therapeutic applications. Although tri-polar transcutaneous electrical stimulation (TENS) is commonly used to change motoneuron excitabi1ity, but the effect of TENS on synaptic activities through dorsal column stimulation or cutaneous pathways is unknown. So, the aim of this research study was to determine the role of cutaneous receptors in conductance of TENS. For this purpose, 10 healthy non-athlete volunteers were tested in three separated sessions, i.e. control 1 (placebo spray and silent TENS), control 2 {lidocaine spray and silent TENS), and experimental (lidocaine spray and TENS) groups. Tri-polar TENS was used on vertebral column (cathode on Tll, one anode 3cm above and another 6cm below the cathode). For evaluation of motoneuron activity, soleus H-reflex and Mh wave recruitment curve were evaluated. We sprayed water (Placebo) and 10% lidocaine on the vertebral column skin under the electrodes for 20 sec. In the experimental session, tripolar TENS on desensitized skin of the vertebral column was applied. TENS was applied for 15 minutes with a frequency of 100 Hz and a pulse width of 300 µs. The results showed that Hmax evocation intensity decreases after application of placebo and lidocaine spray (p<0.05). The positive slope of H-reflex recruitment curve also increased after application of placebo and lidocaine spray (p<0.05). Based on the above results, we suggest a theory to explain the change of synaptic activities of spinal cord as foIlows: Low-threshold cutaneous receptors diminish the pre-synaptic inhibition of la afferent fibers and application of TENS on the desensitized skin increases fit L5 slope and decreases fit L3 slope of H-reflex recruitment curve. In this study, since only low-threshold cutaneous receptors were inhibited, therefore, the role of cutaneous receptors in conductance of TENS could not be ignored.

Volume 9, Issue 2 (11-2005)

Vahid Sheibani, Sahel Motaghi, Rasool Farazifard, Hossein Joneidi, Mohammad Reza Afarinesh,
Volume 10, Issue 2 (3-2006)

Introduction: It is believed that Locus Coeruleus (LC) influences the sensory information processing. However, its role in cortical surround inhibitory mechanism is not understood. In this experiment, using controlled mechanical displacement of whiskers we investigated the effect of phasic electrical stimulation of LC on response of layer V barrel cortical neurons in anesthetized rat. Methods: LC was stimulated 0, 50, 100, 200 and 400ms before principal or adjacent whiskers deflection. For assessing the effect of LC stimulation on inhibitory receptive field of the barrel neurons, adjacent whisker was also deflected 20ms before principal whisker deflection, and LC stimulation was applied 0-400ms before principal whisker displacement. Results: We found that LC stimulation increased the response magnitude of layer V neurons to principal whisker deflection (significance level (p<0.05) at 50-400ms intervals). This increase in response magnitude was observed to adjacent whisker deflection too (significant (p<0.01) at 100ms interval). The response latency of neurons was decreased when LC was stimulated 400ms before principal whisker deflection (p<0.01). LC stimulation did not affect the neuronal response latency to adjacent whisker displacement or spontaneous activity of neurons. Inhibitory effect of adjacent whisker deflection on neuronal response magnitude was increased by LC stimulation when tested when combined whisker displacement. Conclusion: These findings suggest that LC by modulating the neuronal responses enhances the neuronal responsiveness to sensory stimuli and increases their surround inhibition in cortex.
Parviz Ghorbani Moghadam, Mohammad Mohammad-Zadeh,, Javad Mirnajafi-Zadeh, Yaghub Fathollahi,
Volume 10, Issue 3 (11-2006)

Introduction: Electrical low-frequency stimulation (LFS) has antiepileptic effect, but the role of different stimulation parameters on this effect has not been determined. In this study the effect of different LFS parameters (intensity, pulse duration and train duration) on piriform-cortex kindled seizures was investigated. Methods: Seizure was produced in animals using kindling model of epilepsy. Then, the effect of LFS on seizure severity was investigated. Results: Different patterns of LFS (1 Hz) applied immediately before kindling stimulation in fully kindled animals, had no significant effect on seizure parameters. In the second experiment, effect of LFS (1 Hz) on inter-seizure interval was investigated. Data showed that daily stimulation of animals for 15 min with LFS for one week after the last kindling stimulation reduced significantly stage 5 seizure duration. Application of the same LFS protocols for three days and two weeks had no significant effect on seizure parameters. In the third experiment, effect of LFS (1 Hz) on kindling rate was investigated. Results showed that when LFS was delivered daily after each kindling stimulation it could decrease afterdischarge duration in various days during kindling and delayed the appearance of seizure stages 1 and 2 significantly. Conclusion: It may be concluded that LFS has antiepileptic effects on kindling acquisition and inter-seizure interval in kindled animals and that the characteristics of LFS protocol (intensity, pulse duration and train duration) have an essential role on these effects.
Safoura Raufi, Hojjatollah Alaii,
Volume 10, Issue 4 (1-2007)

Introduction: Opiates cause dependency via affect on central nervous system. Locus coeruleus nucleus is a main group of noradrenergic neurons in the brain that plays an important role in the expression of opioid withdrawal signs. During opioid withdrawal, brain waves change in addition to physical and behavioral signs. In this study, we examined the effects of locus coeruleus electrical stimulation on brain waves of morphine dependent rats. Methods: Ten male Wistar rats were given intraplantar injections of increasing doses of morphine for 9 days. On day 10 after induction of anesthesia, electroencephalogram (EEG) recording was done. The EEG recording was also continued after intraplantar injection of naloxone. In the next step, rats were placed in stereotaxic apparatus and following the electrical stimulation of locus coeruleus, EEG was also recorded. Results: Naloxone Injection increased the power of delta waves (P<0.05) and decreased the power of theta waves (P<0.01). The power of alpha waves and beta waves had not significant changes following naloxone administration. Electrical stimulation of locus coeruleus, decreased the power of delta waves(P<0.01) and increased the power of alpha waves (P<0.05) , but did not change the power of theta and beta waves. The EEG total power increased during the withdrawal and decreased following electrical stimulation of locus coeruleus. Conclusion: The changes in EEG due to naloxone administration which reversed toward the basal level after electrical stimulation of locus coeruleus suggests that violence of the locus coeruleus activity by its electrical stimulation in withdrawal stage, results in a compensative reaction in order to attenuation the effects of hyperactivity of the locus coeruleus.
Mehdi Sadegh, Javad Mirnajafi-Zadeh, Mohammad Javan, Yaghoub Fathollahi, Mohammad Mohammad-Zadeh, Ali Jahanshahi, Zahra Deljo,
Volume 11, Issue 1 (4-2007)

Introduction: Low-frequency stimulation (LFS) has a delaying effect on kindled seizures acquisition. In the present study we examined the role of galanin receptors in the inhibitory effects of LFS on kindled seizures induced by electrical stimulation of perforant path. Methods: Animals were stimulated daily at the AD threshold intensity with a rapid kindling procedure. LFS was applied immediately after cessation of each kindling stimulation. M35 (0.5 and 1.0 nM per site), a nonselective galanin receptor antagonist, was microinjected daily into the dentate gyrus before the beginning of stimulation protocol and behavioral seizure stages and afterdischarge durations were recorded. Results: LFS application had a suppressive effect on the kindling rate. It significantly increased the number of stimulations needed to reach seizure stages 3, 4 and 5. LFS also decreased the cumulative afterdischarge duration during the days of stimulation. Intra-dentate gyrus microinjection of M35 reduced the inhibitory effect of LFS on kindling rate, significantly. Conclusion: These data indicate that galanin receptors may have a role in mediating part of the inhibitory effects of LFS on perforant path kindled seizures.
Mohammad Mohammad-Zadeh, Javad Mirnajafi-Zadeh, Yaghoub Fathollahi, Mohammad Javan, Parviz Ghorbani,
Volume 11, Issue 2 (8-2007)

Introduction: Previous studies have been shown that low frequency stimulation (LFS) has an inhibitory effect on kindling acquisition. However, the mechanism of this effect has not been completely determined. In the present study, the effect of LFS of the perforant path on seizures induced by rapid perforant path kindling was investigated. Methods: Animals were kindled by electrical stimulation of perforant path. One group of animals (n=6) received LFS (0.1 ms pulses at 1 Hz, 200 pulse, and 50-150 µA) after termination of each kindling stimulations. In control groups, animals received only kindling stimulations (n=8) or LFS (n=4). Basal field potential recording and paired pulse stimulations were done before kindling stimulations every days. Results: Application of LFS significantly retarded the kindling acquisition and increased the number of stimulations to achieve different seizure stages [F(4,60)=10.9, P<0.0001]. LFS also prevented increment of slope of field excitatory postsynaptic potentials and population spike amplitude during kindling (P<0.001) (There was %88.6±1.7 increment in fEPSP and %94±2.3 increment in PS in kindled group and %3.5±.05 increment in fEPSP and %12.3±0.1 decrease in PS in kindled+LFS group). In addition, LFS prevented the marked increase in early (10-50 ms intervals) and late (300-1000 ms intervals) paired pulse depression induced by kindling significantly (P<0.01). Conclusion: According to obtained results, it may be suggested that LFS of perforant path has a significant antiepileptogenic effect on perforant path kindled seizures through inhibition of synaptic transmission in dentate gyrus. Meanwhile, LFS prevents compensatory increase in the paired pulse depression during kindling acquisition.
Tahereh Zeinali, Javad Mirnajafi-Zadeh, Vahid Sheibani, Mohammad Eza Palizvan, Mehdi Abbasnejad,
Volume 11, Issue 3 (12-2007)

Epilepsy is among the most common disorders of the central nervous system and there is not an absolute method for its treatment. It has been shown that each seizure has a depressing effect on the following seizure. Thus, finding the mechanisms responsible in this phenomenon can improve our knowledge toward new ways for epilepsy treatment. In this study, the role of adenosine A1 receptors in post seizure depressing period was investigated in amygdala kindling model of epilepsy. Methods: Rats were kindled by daily electrical stimulation of amygdala. At first, different groups of kindled animals were stimulated at different times after the first stimulation and the percent of suppression of seizure parameters were calculated. Then, 8-cyclopenthyl-1, 3-dimethylxanthine (CPT), a selective adenosine A1 receptor antagonist (50 and 200 μM) were intracerebroventricularly microinjected before the second stimulation and its effect on percent of suppression induced by the first stimulation was investigated. Results: In the second stimulation, applied at 10 and 30 min after the first stimulation, the seizure parameters were significantly reduced. CPT microinjection (50 and 200 μM) significantly decreased the percent of suppression of seizure parameters. This decrease was significant at 10 and 30 min after the first stimulation with compare to the groups received the drug solvent. Conclusion: Obtained results showed that endogenous adenosine has a role in post seizure depression period through A1 receptors. As the blocking of A1 receptors by CPT could not completely prevent this period, other factors may also play role in this suppression.
Alireza Sarmadi, Seyyed Mohammad Firoozabadi, Giti Torkaman, Yaghoub Fathollahi,
Volume 13, Issue 2 (8-2009)

Abstract: To assess the effect of penetration depth of the surface tripolar electrical stimulation, Tripolar TENS was applied with different intensities (equal to sensory threshold (ST), 1.25 ST, 1.5 ST) on vertebral column of twenty healthy and three hemiplegic subjects. The cathode of TENS was laid on the T11 vertebra and anodes were put 3cm apart from cathode, longitudinally and in the anode-cathode-anode arrangement. Before, after and 10 min after TENS the recruitment curve of soleus and gastrocnemius H-reflex and M wave were recorded. Experiments were done in four separate sessions. One of them was control session and the TENS apparatus was off in it. In each of the test sessions, TENS was applied with one of the intensities. The results showed that the 1.5 ST TENS have a complex facilitatory-inhibitory effect on recruitment curve of soleus H-reflex in the way that slow motoneurons were inhibited and fast motoneurons were facilitated. So the positive slope of curve was increased and the intensity needed to evoke Hmax was decreased. Amplitude of Hmax and threshold of the curve were slightly decreased. Gastrocnemius was facilitated after 1.5 ST TENS. The threshold of the H-reflex curve and needed intensity to evoke Hmax were decreased, while peak to peak amplitude of Hmax was increased. After ST TENS, soleus was facilitated and gastrocnemius had little change. It seems that 1.5 ST TENS facilitate Ia, Ib, fast motoneurons and renshaw cells via stimulating the dorsal column of the cord and renshaw inhibit slow motoneurons, so a complex of facilitation and inhibition appears in soleus motoneurons. In the case of gastrocnemius which the renshaw cells had not strong effect, H-reflex curve was facilitated. In ST TENS which only the skin afferents were stimulated the renshaw cells were inhibited by skin afferents and H-reflex was facilitated, But because the gastrocnemius motoneurons are slightly under control of renshaw and skin afferents synapses with motoneurons are not engaged in reflex loop, facilitation of skin afferents synapses after TENS application had no effect on the H-reflex parameters of gastrocnemius.
Ali Siyahposht Khachaki, Vahid Sheibani, Mohammad Reza Afarinesh Khaki, Hamid Sheikhkanloui Milan, Ali Shamsizadeh,
Volume 13, Issue 4 (1-2010)

Introduction: Barrel cortex of rodents is responsible for sensory information processing from muzzle whiskers. Locus coeruleus (LC) as the main source of norepinephrine (NE) in the cortex, is effective on the sensory information processing. Methods: Rats were divided to 2 groups. One group underwent sensory deprivation (P4) and the other group served as control and did not undergo sensory deprivation. Response properties of the neurons were evaluated by extracellular single unit recordings following a controlled mechanical deflection of the principal whisker (spared whisker), or before the simultaneous deflection of principal and adjacent whiskers (trimmed whisker) were assessed. In the P4 group, all whiskers on the left muzzle, except D2, were trimmed every other day for two months. In both groups, LC was electrically stimulated 0, 50, 100, 200, 400 and 800 ms before controlled principal whisker deflection. Response magnitude, latency and CTR index (lateral inhibition index) were assessed. Results: In the P4 group, deflection of the principal whisker without LC electrical stimulation, increased the response magnitude and CTR index, but decreased the response latency compared to the control group. The magnitude of the response of neurons to the principal whisker deflection was significantly different between P4 and control groups, in following of principal whisker deflection in times of LC stimulation showed significant difference only in 50 ms subgroup. In both groups, pro-stimulation differences in CTR index and response latency remained unchanged after LC stimulation. Conclusion: Our data showed that electrical stimulation of LC following sensory deprivation modulates neuronal response properties and changes their response pattern.
Maryam Zeraati, Javad Mirnajafi-Zadeh, Mohammad Javan, Saeed Semnanian, Simin Namvar,
Volume 14, Issue 2 (7-2010)

Introduction: Considering high prevalence of epileptic disease and considering that 40 percent of epileptic patients are resistant to drug therapy, it needs more researches to find new therapeutic ways. LFS is among the new methods for epilepsy treatments. One possible mechanism involved in the anticonvulsant effect of LFS is increased adenosine. Therefore, in this study the role of adenosine production from ATP by ectonucleotidase enzyme pathway in exerting the anticonvulsant effects of LFS were evaluated. Methods: Animals were kindled by electrical stimulation of perforant path in a rapid kindling manner (12 stimulation per day). One group of animals received LFS after kindling stimulation. In one another group, AOPCP a blocker of ectonucleotidase inhibitor was micro injected (50 micro molar) intra cerebro ventricular each day before LFS stimulation. Some group of animals were also received AOPCP (50 and 100 micro molar) but were not applied to LFS. Seizure behavior and electrophysiological parameters (including ADD and field potential) were recorded. Results: Like previous investigations, application of LFS, decreased all seizure parameters significantly. Microinjection of AOPCP had no significant effect on anticonvulsant actions of LFS. However microinjection of AOPCP at doses of 100 micro molar in animals that received just kindling stimulations, increased the seizure parameters significantly. Conclusion: The results show that adenosine production via ectonucleotidase enzyme pathway may has no role in anticonvulsant effects of LFS however endogenous adenosine produced through this pathway has an important role in kindling development.

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