Microstimulation of the supplementary motor area (SMA) in the awake monkey

The supplementary motor area of three Macaca fascicularis was mapped using intracortical microstimulation (ICMS). Both forelimb and hindlimb movements were evoked using currents of 30 microA or less. However, thresholds for evoking movements were higher than those in the primary motor cortex. Proximal motor effects predominated, but distal joint movements were also elicited. Forelimb points were clustered in mesial cortex of area 6, anterior to the precentral hindlimb and tail region. Distal joint effects were located deep in the cortex, intermingled with proximal effects. Hindlimb response which were less spatially localized, were found both ventral to the forelimb area, in the dorsal bank of the cingulate sulcus, and in mesial cortex, well anterior to area 4. No movements of facial muscles were elicited. Injections of HRP were made into the spinal cord at the cervical level in two animals and the lumbar level in the third one. An area of labelled cells was seen in mesial area 6 which corresponded closely to the region from which ICMS effects were elicited. No movements were evoked from the anterior portions of the fundal region of the cingulate sulcus which were also labelled.

Extracorporeal shockwave application to the distal femur of rabbits diminishes the number of neurons immunoreactive for substance P in dorsal root ganglia L5

Application of extracorporeal shockwaves to the musculoskeletal system can induce long-term analgesia in the treatment of chronic painful diseases such as calcifying tendonitis of the shoulder, tennis elbow and chronic plantar fasciitis. However, the molecular and cellular mechanisms underlying this phenomenon are largely unknown. Recently it was shown that application of extracorporeal shockwaves to the distal femur of rabbits can lead to reduced concentration of substance P in the shockwaves' focal zone. In the present study we investigated the impact of extracorporeal shockwaves on the production of substance P within dorsal root ganglia in vivo. High-energy shockwaves were applied to the ventral side of the right distal femur of rabbits. After six weeks, the dorsal root ganglia L5 to L7 were investigated with high-precision design-based stereology. The application of extracorporeal shockwaves caused a statistically significant decrease in the mean number of neurons immunoreactive for substance P within the dorsal root ganglion L5 of the treated side compared with the untreated side, without affecting the total number of neurons within this dorsal root ganglion. No effect was observed in the dorsal root ganglia L6 and L7, respectively. These data might further contribute to our understanding of the molecular and cellular mechanisms in the induction of long-term analgesia by extracorporeal shockwave application to the musculoskeletal system.

Corticospinal neurones of the supplementary motor area of monkeys. A single unit study

The direct projection from the supplementary motor area (SMA) to the spinal cord was investigated in six monkeys by means of antidromic identification of single SMA neurones. The exploration concentrated on that portion of medial area 6 from which movements were found to be elicited by stimulation at intensities of less than 30 microA in an earlier study, but also included some of medial area 4. Of 315 identified corticofugal projection neurones, 234 were found to be localized within medial area 6; of these only one third (76 cells) were corticospinal cells and the remaining two thirds were neurones which projected to the brainstem. The conduction velocities of the descending projection neurones of the SMA were slow (modal value: 10 m/s). Corticospinal cells of the SMA were found up to 6 mm rostral to the boundary between areas 4 and 6. Corticospinal neurones activated antidromically from the cervical but not from the lumbar cord ('cervico-thoracic' neurones) were concentrated in the mesial cortex; 'lumbo-sacral' neurones were found both in the dorsal cortex and the dorsal bank of the cingulate sulcus. However, there was considerable intermingling between the two types of projection neurones and there was no separation in the rostro-caudal direction. Similarly, projection neurones receiving orthodromic inputs from the somatotopical subdivisions of the precentral cortex were not segregated, but were intermingled in the entire rostro-caudal extent of the SMA. It is concluded that there is a clustering of corticospinal neurones in the SMA according to their most caudal segmental projection. However, no rostro-caudal differentiation into face, arm and leg areas was established. This observation is consistent with the results of a previous study in which corticospinal neurones in the SMA were labelled with anatomical tracers and efferent zones were investigated with intra-cortical microstimulation (Macpherson et al. 1982).

Evidence that sodium nitroprusside possesses anticonvulsant effects mediated through nitric oxide

The effect of sodium nitroprusside (SNP) on epileptiform activity elicited by administration of penicillin (500 units) into the somatomotor cortex was studied in anaesthetized rats. No epileptiform activity was observed after intracortical microinjection of SNP (5 and 20 nM). Microinjection of penicillin into the somatomotor cortex induced epileptiform activity in electrocorticograms (ECoG). Epileptiform discharges elicited by penicillin were significantly decreased by SNP. The effect of SNP appeared within 1 min of application and lasted for 2-5 min. The inhibitory effect of SNP on epileptiform activity could be prevented by pretreatment with methylene blue (20 nM), a soluble guanylate cyclase inhibitor. Prior injection of haemoglobin (5 microliter), a nitric oxide (NO) scavenger, prevented the anticonvulsant effect of SNP. These results suggest that NO may be an endogenous anticonvulsant substance.

Anticonvulsant effects of melatonin on penicillin-induced epileptiform activity in rats

In the present study, we investigated the effects of melatonin on penicillin-induced epileptiform activity in female Wistar rats. The left cerebral cortex was exposed by craniotomy under urethane anesthesia for the induction of epilepsy by intracortical microinjection of penicillin (200 IU) into the left sensorimotor cortex. The epileptiform activity was analyzed by electrocorticogram (ECoG). Ten minutes before the penicillin injection, 20, 40 or 80 microg of melatonin was administered intracerebroventricularly and ECoG was monitored for 1 h. Forty or 80 microg of melatonin significantly increased the latency to epileptiform activity. Furthermore, melatonin significantly decreased the frequency of spike and spike-wave activity, whereas the amplitude of spikes remained unchanged. In conclusion, data obtained from the present study suggest that melatonin suppresses penicillin-induced epileptiform activity, and it may be an endogenous anticonvulsant.

Anticonvulsant effects of focal and intracerebroventricular adenosine on penicillin-induced epileptiform activity in rats

Adenosine has potent anticonvulsant effects on various models of experimental epilepsy. In the present study, we examined the effects of focal and intracerebroventricular (i.c.v.) adenosine on penicillin-induced epileptiform activity in Wistar rats. The effects of theophylline, a non-selective adenosine receptor antagonist, were also researched. The recordings of electrocorticogram (ECoG) were carried out by using a data acquisition system, under urethane anesthesia. Adenosine was given in doses of 1, 10 and 100 microg/rat via focal and i.c.v. 30 min after penicillin administration. Theophylline was injected in doses of 1, 10 and 100 microg/rat by i.c.v. too. Adenosine administration significantly decreased the spike frequency while theophylline increased. Focal adenosine is more effective than i.c.v. adenosine. 100 microg adenosine is an effective dose that causes a decrease in epileptiform activity during experiments. We also demonstrated that 100 microg theophylline significantly increased epileptiform activity. Our findings suggest that focal adenosine is more effective than i.c.v. adenosine on epileptiform activity.

Detailed spectral profile analysis of penicillin-induced epileptiform activity in anesthetized rats

Penicillin model is a widely used experimental model for epilepsy research. In the present study we aimed to portray a detailed spectral analysis of penicillin-induced epileptiform activity in comparison with basal brain activity in anesthetized Wistar rats. Male Wistar rats were anesthetized with i.p. urethane and connected to an electrocorticogram setup. After a short period of basal activity recording, epileptic focus was induced by injecting 400IU/2 microl penicillin-G potassium into the left lateral ventricle while the cortical activity was continuously recorded. Basal activity, latent period and the penicillin-induced epileptiform activity periods were then analyzed using both conventional methods and spectral analysis. Spectral analyses were conducted by dividing the whole spectrum into different frequency bands including delta, theta (slow and fast), alpha-sigma, beta (1 and 2) and gamma (1 and 2) bands. Our results show that the most affected frequency bands were delta, theta, beta-2 and gamma-2 bands during the epileptiform activity and there were marked differences in terms of spectral densities between three investigated episodes (basal activity, latent period and epileptiform activity). Our results may help to analyze novel data obtained using similar experimental models and the simple analysis method described here can be used in similar studies to investigate the basic neuronal mechanism of this or other types of experimental epilepsies.

Protective effects of melatonin and omega-3 on the hippocampus and the cerebellum of adult Wistar albino rats exposed to electromagnetic fields

The purpose of the study was to investigate the effects of pulsed digital electromagnetic radiation emitted by mobile phones on the central nervous system of the adult Wistar albino rats. The study evaluated structural and functional impacts of four treatment arms: electromagnetic field (EMF) exposed; EMF exposed + melatonin treated group (EMF + Mel); EMF exposed + omega-3 (ω3) treated group (EMF + ω3); and control group (Cont). The 12-weeks-old rats were exposed to 900 MHz EMF for 60 min/day (4:00–5:00 p.m.) for 15 days. Stereological, biochemical and electrophysiological techniques were applied to evaluate protective effects of Mel and ω3. Significant cell loss in the CA1 and CA2 regions of hippocampus were observed in the EMF compared to other groups (p < 0.01). In the CA3 region of the EMF + ω3, a significant cell increase was found compared to other groups (p < 0.01). Granular cell loss was observed in the dentate gyrus of the EMF compared to the Cont (p < 0.01). EMF + ω3 has more granular cells in the cerebellum than the Cont, EMF + Mel (p < 0.01). Significant Purkinje cell loss was found in the cerebellum of EMF group compared to the other (p < 0.01). EMF + Mel and EMF + ω3 showed the same protection compared to the Cont (p > 0.05). The passive avoidance test showed that entrance latency into the dark compartment was significantly shorter in the EMF (p < 0.05). Additionally, EMF had a higher serum enzyme activity than the other groups (p < 0.01). In conclusion, our analyses confirm that EMF may lead to cellular damage in the hippocampus and the cerebellum, and that Mel and ω3 may have neuroprotective effects.

Effects of L-arginine on penicillin-induced epileptiform activity in rats

It has been suggested that nitric oxide (NO) is involved in the pathophysiology of epilepsy. Data are, however controversial because it is not clear whether NO has pro- or anticonvulsant effects. The aim of this study was to investigate the effects of NO on penicillin G-induced epileptiform activity. The left cerebral cortex was exposed by craniotomy in urethane-anesthetized Wistar rats. The epileptic activity was produced by intraperitoneal injection of penicillin G (3 million U/kg, i.p.). The ECoG (electrocorticogram) activity was displayed on a four-channel recorder. At 39.7 +/- 5.4 min after penicillin administration, large amplitude sharp waves appeared in the ECoG. Mean spike frequency and mean spike amplitude were calculated as 29.5 +/- 3.2/min and 865 +/- 91 microV, respectively, at the 55th min. 7-Nitroindazole (60 mg/kg, i.p.) injection 30 min before penicillin G administration significantly reduced the latency of epileptiform activity. Intracerebroventricular administration of L-arginine (300 microg/2 microl, i.c.v.) and sodium nitroprusside (100 microg/2 microl, i.c.v.) suppressed epileptiform activity. Saline (2 microl) and D-arginine (300 microg/2 microl, i.c.v.) administration into the cerebral ventricle were completely ineffective on epileptiform activity (P<0.01). These findings suggest that NO may be an endogenous antiepileptic substance.

EFFECTS OF NITRIC OXIDE ON PASSIVE AVOIDANCE LEARNING IN RATS

To investigate the effects of nitric oxide (NO) on passive avoidance learning, L-NAME, D-NAME, and L-arginine were administered i.p. 30 min prior to learning trial; the effects of these substances were tested 24 h later using a passive avoidance apparatus in rats. To reveal the effect of NO on consolidation of acquired memory, L-NAME, D-NAME, and L-arginine were administered i.p. immediately after learning trials and animals were tested 24 h later. Effect of NO on retention was also investigated by injecting L-NAME, D-NAME, and L-arginine (same dosages) 30 min prior to 24 h testing (retrieval). L-NAME administered 30 min before and 24 h after learning trial significantly decreased the avoidance latency but there was no significant effect on consolidation. L-Arginine appeared to enhance the retention of acquired memory significantly, whereas D-NAME had no effect on any testing regime. The results suggest that NO may be involved in learning and retention of passive avoidance.

Electrocorticographic effects of topically applied scopolamine

The electrocorticographic effects of topically applied scopolamine were investigated in unanesthetized cats with high cervical transection. After subpial injection of 30 cumu scopolamine in concentrations of 10 to 20%, large amplitude intermittent sharp waves appeared in the electrocorticogram, which developed into long-lasting paroxysmal activity. This effect was antagonized by intravenous eserine, 0.1 mg/kg, when it was produced by topical scopolamine in low dosage. The acoustically evoked cortical response and the generalized epileptiform activity produced by topical succinylcholine disappeared after topical scopolamine in low dosage. It is suggested that the seizure-suppressing effect of scopolamine may be due to its cholinolytic action. The convulsive activity of topical scopolamine in high concentrations may be accounted for by its depolarizing, synchronizing, disinhibiting, and acetylcholine-releasing effects.

Further evidence for the role of nitric oxide in maternal aggression: effects of L-NAME on maternal aggression towards female intruders in Wistar rats

It has been shown that nitric oxide (NO) increases aggression in male mice, whereas it decreases aggression in lactating female mice and prairie voles. It is also known that aggression can be exhibited at different levels in rodent species, strain or subtypes. The aims of this study were to investigate the proportion of aggressiveness in Wistar rats, the effect of intraperitoneally administered nonspecific nitric oxide synthase (NOS) inhibitor L-NAME (NG-nitro L-arginine methyl ester) on maternal aggression towards female intruders, and whether these effects are due to NO production or not. Rats were given saline intraperitoneally on the postpartum Day 2 and aggression levels were recorded. The same rats were given 60 mg/kg L-NAME or D-NAME (NG-nitro D-arginine methyl ester) on the postpartum Day 3 and their effects on aggression levels were compared to saline. While L-NAME administration did not cause any differences in the total number of aggressive behavior, aggression duration and aggression intensity, it reduced the proportion of animals showing aggressive behavior. In addition, the latency of the first aggression was significantly increased by L-NAME. In the D-NAME group, however, no significant change was found. Our results have shown that L-NAME reduces maternal aggression towards female intruders in Wistar rats through inhibition of NO production. These results suggest that the role of NO in offensive and defensive maternal aggression shares neural mechanisms.

Do cochlear nuclei contribute to auditory lateralization? A stereological evaluation of neuron numbers

The aim of this study was to estimate the total number of cells in the subdivisions of the cochlear nucleus (CN) of the rat with unbiased stereological methods. The total number of neurons was determined in both the ventral cochlear nucleus (VCN) and the dorsal cochlear nucleus (DCN) to compare the right and left sides. The total cell numbers were 15,280 in the left VCN, 15,400 in the right VCN, 10,260 in the left DCN, and 10,860 in the right DCN. Comparison of the right and left major subdivisions of the CN of the rat showed that there was no significant difference between the right and left sides of the rat CN. This result indicates that the CNs do not contribute to auditory lateralization in the rat in regard to cell numbers.

Effects of spermine and the passive avoidance learning (PAL) following cerebral ischemia in chicks: Association with neuroprotection of pyramidal cells

The aim of this study is to investigate the effects of spermine and the passive avoidance learning on hippocampus following transient cerebral ischemia in the chicks. The study is composed of the pure control (CG), sham (SG) and experimental groups (n=20). Experimental groups (ischemia group, IG and ischemia-spermine group, ISG) were exposed to ischemia for 20min whereas the SG was exposed to sham operation and CG group was not exposed to any operation. Passive avoidance learning (PAL) was applied to the half number of the subjects in each group. Both before and after 7days from the ischemia, operated animals were taken to PAL and then they were sacrificed. Total numbers of neurons in the hippocampus were stereologically estimated using Cresyl violet stained sections. We detected that number of neurons was increased following PAL and especially spermine treatment. According to our results, we suggested that spermine may reduce the deleterious effects of the ischemia by causing to increase in the neuronal number and so, it may be slightly supportive to the PAL.

The effects of the purinergic system on digitalis-induced epileptiform activity

It has been suggested that endogenous chemical substances, such as adenosine, released during a seizure attack, may act as anticonvulsants in vivo. We have investigated electrophysiologically the effects of purinoceptor agonists and antagonists on the epileptiform activity induced by intracortical digitalis in anesthetized rats. Intracortical injections of 1, 2, or 4 micrograms digitalis (desacetyl lanatocid C) caused an epileptiform electrocorticogram (ECoG). The application of adenosine (25 or 100 microM) or adenosine triphosphate (ATP) (3 mM) after desacetyl lanatocid C blocked the epileptiform activity. beta, gamma-Methylene ATP (0.1-0.8 mM), a stable analog of ATP, produced inhibition and then death. The epileptogenic effect of desacetyl lanatocid C was enhanced by theophylline (1 mM); however, suramin (1 mM) changed the pattern of epilepsy. These results indicate that the purinergic system may be involved in the mechanism of action of digitalis glycosides.

Proconvulsant Effect of Papaverine on Penicillin-Induced Epileptiform Activity in Rats

AIM

Papaverine is a vasodilator agent that is an opium alkaloid. It exhibits its effects by inhibiting the phosphodiesterase enzyme. Papaverine administration is widely used to avoid symptomatic vasospasm after subarachnoid hemorrhage. We aimed, in this research, to study the effects of papaverine on the epileptic discharges stimulated by penicillin.

MATERIAL AND METHODS

Adult female Wistar rats (220±30 g) were included in this research (n=30). Rats were anesthetized with urethane (1.25 g/kg) and then the left cerebral cortex was reached by opening a burr hole with a drill. Penicillin G sodium salt (500 IU)(200 IU/1 μl) was injected into the left lateral ventricle to produce epileptiform activity. Thirty minutes before penicillin G sodium injection, papaverine was administered at doses of 5, 10, 20 or 40 mg/kg intraperitoneally.

RESULTS

There was no significant difference in spike frequency between the control group and the groups given 5 mg/kg, 10 mg/ kg or 40 mg/kg papaverine, while 20 mg/kg papaverine significantly increased the spike frequency (p < 0.05).

CONCLUSION

Papaverine augments the epileptiform activity produced by penicillin injection. It is important to remember that papaverine might induce convulsions in patients who have epilepsy. More research is required to understand the mechanisms of the proconvulsant influence of papaverine in epilepsy.