Antinociceptive effects of Raphanus sativus sprouts involve the opioid and 5-HT1A serotonin receptors, cAMP/cGMP pathways, and the central activity of sulforaphane.

Raphanus sativus L. cv. Sango, commonly known as red radish, is widely consumed around the world as a vegetable, but its benefit in pain relief is not sufficiently investigated. This study aimed to evaluate the antinociceptive effects of R. sativus and a possible mechanism of action. An aqueous extract of R. sativus sprouts (AERSS) was investigated by parenteral (10, 30, and 100 mg kg-1, i.p.) and enteral (500 mg kg-1, p.o.) administration in the neurogenic and inflammatory phases of the formalin test, where gastric damage was also evaluated as a possible adverse effect. Ketorolac (5 mg kg-1, i.p.) was used as the reference drug. Endogenous opioid and 5-HT1A serotonin receptors, as well as the cAMP/NO-cGMP pathways, were explored in the study of a possible mechanism of action by using their corresponding antagonists: naloxone, 1 mg kg-1, i.p., WAY100635, 1 mg kg-1, i.p., and enzymatic activators or inhibitors, respectively. Sulforaphane (SFN), a known bioactive metabolite, was analyzed using electroencephalography (EEG) to evidence its central involvement. A significant and dose-dependent antinociceptive activity was observed with the AERSS resembling the antinociceptive effect of the reference drug, with an equivalent significant response with a dose of 500 mg kg-1, p.o. without causing gastric damage. The participation of the endogenous opioid and 5-HT1A serotonin receptors at central and peripheral levels was also observed, with a differential participation of cAMP/NO-cGMP. SFN as one metabolite produced significant changes in the EEG analysis, reinforcing its effects on the CNS. Our preclinical evidence supports the benefits of consuming Raphanus sativus cv. Sango sprouts for pain relief.

Electroencephalographic profile of Salvia amarissima Ortega and amarisolide A in the absence and presence of PTZ-induced seizures in mice.

Salvia amarissima Ortega is a plant used in traditional medicine to treat CNS's affections. Despite its depressant properties in anxiety and fibromyalgia, there is no scientific evidence about its capability to control seizure activity. This study aimed to investigate the effects of the S. amarissima aqueous extract (SAAE) and its metabolite amarisolide A (AMA) on the electrocorticographic (ECoG) activity. The ECoG profiles were previously and concurrently analyzed to the pentylenetetrazole (85 mg/kg, i.p.)-induced seizure behavior after thirty min of the administration of several doses of the SAAE (1, 10, 30, and 100 mg/kg, i.p.) and two doses of AMA (0.5 and 1 mg/kg, i.p.). A dosage of AMA (1 mg/kg,i.p.) was selected to explore a possible mechanism of action by using antagonists of inhibitory receptors such as GABAA (picrotoxin, 1 mg/kg, i.p.) or 5-HT1A of serotonin (WAY100635, 1 mg/kg, i.p.). Significant changes in the frequency bands and the spectral power were observed after the treatment alone. Additionally, SAAE and AMA produced significant and dose-dependent anticonvulsant effects by reducing the incidence and severity of seizures and increasing latency or survival. Both antagonists prevented the effects of AMA in the severity score of seizures and survival during the tonic-clonic seizures. In conclusion, our preclinical data support that S. amarissima possesses anticonvulsant properties, in part due to the presence of amarisolide A, mediated by different inhibitory mechanisms of action. Our scientific evidence suggests that this Salvia species and amarisolide A are potential neuroprotective alternatives to control seizures in epilepsy therapy.

Antidepressant- and anxiolytic-like activities and acute toxicity evaluation of the Psilocybe cubensis mushroom in experimental models in mice.

ETHNOPHARMACOLOGY RELEVANCE: Central nervous system (CNS) diseases can be diverse and usually present with comorbidity, as in the case of depression and anxiety. Despite alternatives like Psilocybe mushrooms for mental health there is no basic research to evidence their CNS benefits. AIM OF THE STUDY: To evaluate the anxiolytic- and antidepressant-like effects, as well as the acute toxicity of P. cubensis mushroom. MATERIAL AND METHODS: First, the acute toxicity (LD50) of P. cubensis (2000 mg/kg) was determined after the esophageal (p.o.) and intraperitoneal (i.p.) route of administration. The rota-rod test and electroencephalogram (EEG) were included to assess CNS toxicity in free moving mice. Anxiolytic (ambulatory or exploratory and rearing behaviors) and antidepressant behavioral responses were assayed in the open-field, plus-maze, and forced swimming test, respectively, after administration of 1000 mg/kg, p.o., of the whole P. cubensis mushroom or the polar aqueous (AQ) or methanolic (MeOH) extractions (1, 10, and/or 100 mg/kg, i.p.) in comparison to the reference drugs buspirone (4 mg/kg, i.p.), fluoxetine and/or imipramine (10 mg/kg, s.c. and i.p., respectively). A chemical analysis of the AQ and MeOH extractions was performed to detect psilocybin and/or psilocin by using UHPLC. RESULTS: Neurotoxic effects of P. cubensis mushroom administered at high doses were absent in mice assessed in the rota-rod test or for EEG activity. A LD50 > 2000 mg/kg was calculated by p.o. or i.p. administration. While significant and/or dose-response antidepressant-like effects were produced with the whole P. cubensis mushroom, p.o., and after parenteral administration of the AQ or MeOH extractions resembling the effects of the reference drugs. Behavioral responses were associated with an anxiolytic-like effect in the open-field as corroborated in the plus-maze tests. The presence of psilocybin and psilocin was mainly characterized in the AQ extraction. CONCLUSION: Our results provide preclinical evidence of the anxiolytic- and antidepressant-like effects of the P. cubensis mushroom without producing neurotoxicity after enteral or parenteral administration, where psilocybin and psilocin were identified mainly after AQ extraction. This study reinforces the benefits of the P. cubensis mushroom in mental health and therapy for anxiety and depression.

Anxiolytic-like Effects and Quantitative EEG Profile of Palmitone Induces Responses Like Buspirone Rather Than Diazepam as Clinical Drugs.

Anxiety is a mental disorder with a growing worldwide incidence due to the SARS-CoV-2 virus pandemic. Pharmacological therapy includes drugs such as benzodiazepines (BDZs) or azapirones like buspirone (BUSP) or analogs, which unfortunately produce severe adverse effects or no immediate response, respectively. Medicinal plants or their bioactive metabolites are a shared global alternative to treat anxiety. Palmitone is one active compound isolated from Annona species due to its tranquilizing activity. However, its influence on neural activity and possible mechanism of action are unknown. In this study, an electroencephalographic (EEG) spectral power analysis was used to corroborate its depressant activity in comparison with the anxiolytic-like effects of reference drugs such as diazepam (DZP, 1 mg/kg) and BUSP (4 mg/kg) or 8-OH-DPAT (1 mg/kg), alone or in the presence of the GABAA (picrotoxin, PTX, 1 mg/kg) or serotonin 5-HT1A receptor antagonists (WAY100634, WAY, 1 mg/kg). The anxiolytic-like activity was assayed using the behavioral response of mice employing open-field, hole-board, and plus-maze tests. EEG activity was registered in both the frontal and parietal cortex, performing a 10 min baseline and 30 min recording after the treatments. As a result, anxiety-like behavior was significantly decreased in mice administered with palmitone, DZP, BUSP, or 8-OH-DPAT. The effect of palmitone was equivalent to that produced by 5-HT1A receptor agonists but 50% less effective than DZP. The presence of PTX and WAY prevented the anxiolytic-like response of DZP and 8-OH-DPAT, respectively. Whereas only the antagonist of the 5-HT1A receptor (WAY) inhibited the palmitone effects. Palmitone and BUSP exhibited similar changes in the relative power bands after the spectral power analysis. This response was different to the changes induced by DZP. In conclusion, brain electrical activity was associated with the anxiolytic-like effects of palmitone implying a serotoninergic rather than a GABAergic mechanism of action.

Protective Effect of Tilia americana var. mexicana Against Kainic Acid-induced Damage in Brain, Liver, and Kidney: Behavioral and Biochemical Changes.

Tiliaamericana var. mexicana (Tilia) possesses anticonvulsant, antioxidant, neuroprotective, and hepatoprotective activities. The spectrum of anticonvulsant activity in status epilepticus models has not been sufficiently explored. We evaluated the effects of ethyl acetate (EAc), and methanol (ME) extracts on kainic acid (KA)-induced seizures by measuring rats'behavior (severity and latency) and lipoperoxidation in different brain areas (cerebellum, brain hemispheres, cortex, and medulla), kidneys, and liver. Male Wistar rats were administered KA (10 mg/kg, i.p.) after three days of pretreatment with Tilia extract (100 mg/kg). The EAc and ME Tilia extracts significantly decreased the severity of phase 1 and phase 2 seizures, respectively. The ME Tilia extract increased the latency to seizure (27 ± 2 min) compared to the control (13 ± 2 min). The ME and EAc Tilia extracts significantly prevented the increased lipid peroxidation caused by KA-induced seizures in the cerebellum, brain hemispheres, cortex, medulla, liver, and kidneys. The vehicle olive oil (OO) also showed anticonvulsant effects, decreasing the severity of seizures to phase 3 and lipoperoxidation levels in the cerebellum, brain hemispheres, cortex, medulla, liver, and kidneys. The anticonvulsant activity of Tilia is mediated by antioxidant effects in central and systemic areas that involve synergistic interactions among the chemical constituents of these extracts (glucosides of quercetin and kaempferol), while vehicle OO showed the same effects, probably due to its constituent oleuropein.

Antinociceptive and gastroprotective activities of Bocconia arborea S. Watson and its bioactive metabolite dihydrosanguinarine in murine models.

ETHNOPHARMACOLOGICAL RELEVANCE: Bocconia arborea S. Watson (Papaveraceae) is known as "palo llora sangre" and is used in Mexican traditional medicine for the treatment of infections, it is also used as anxiolytic, analgesic, and antidiabetic, among others. AIM OF THE STUDY: to evaluate the antinociceptive and gastroprotective activities of extracts from B. arborea and dihydrosanguinarine (DHS) in murine models. MATERIALS AND METHODS: Organic extracts [hexane (HEX), dichloromethane (DCM) and methanol (MeOH)] were obtained by maceration. DHS was isolated and purified from HEX and DCM by precipitation and chromatographic column, respectively. Organic extracts and DHS were evaluated to determine their antinociceptive effect using formalin test in murine model. Also, the ambulatory effect of the HEX and DHS was determined in Open field test. The possible mechanism of action of DHS was explored in the presence of naltrexone (NTX, 1 mg/kg, i.p.), and picrotoxin (PTX, 1 mg/kg, i.p.). Gastric damage as possible adverse effect or gastroprotection were also investigated. Whereas DHS acute toxicological study was done, and 100 mg/kg of DHS was examined by electroencephalographic (EEG) analysis to discard neurotoxic effects. RESULTS: The B. arborea extracts significantly showed effects in both neurogenic and inflammatory phases of the formalin test, where the HEX extract reached the major antinociceptive effect. A significant and dose-response (10, 30, and 100 mg/kg) antinociceptive activity was observed with the HEX (ED50 = 69 mg/kg) and DHS (ED50 = 85 mg/kg) resembling the effect of the reference analgesic drug tramadol (30 mg/kg). The significant effect of DHS was inhibited in the presence of NTX and PTX. Neither the extracts or DHS produced sedative effects or gastric damage per se at antinociceptive doses. The EEG analysis demonstrated central depressant activity but not sedative or neurotoxic effects at the highest antinociceptive dosage tested, and LD50 is higher than 2000 mg/kg. CONCLUSIONS: HEX, DCM, and MeOH extracts showed significant antinociceptive activity, and DHS was identified as one of bioactive compounds without producing sedative, neurotoxic or gastric damage effects, as possible adverse effects reported for analgesic drugs. A role of opioid and GABAA neurotransmission appears to be involved as mechanisms of action of DHS, suggesting its potential for pain therapy and reinforcing the traditional use of B. arborea.

Tabernaemontana arborea and ibogaine induce paroxysmal EEG activity in freely moving mice: Involvement of serotonin 5-HT1A receptors.

Several Apocynaceae species, most notably Tabernanthe iboga, Voacanga africana and many Tabernaemontana species, produce ibogan-type alkaloids. Although a large amount of information exists about the Tabernaemontana genus, knowledge concerning chemistry and biological activity remains lacking for several species, especially related to their effects on the central nervous system (CNS). The aim of this study was to evaluate the effect of Tabernaemontana arborea Rose ex J.D.Sm. (T. arborea) hydroalcoholic extract (30, 56.2 and 100 mg/kg, i.p.) and two of its main alkaloids (ibogaine and voacangine, 30 mg/kg, i.p.) on electroencephalographic (EEG) activity alone and in the presence of the chemical convulsant agent pentylenetetrazole (PTZ, 85 mg/kg, i.p.) in mice. EEG spectral power analysis showed that T. arborea extract (56.2 and 100 mg/kg) and ibogaine (30 mg/kg, i.p.) promoted a significant increase in the relative power of the delta band and a significant reduction in alpha band values, denoting a CNS depressant effect. Voacangine (30 mg/kg, i.p.) provoked an EEG flattening pattern. The PTZ-induced seizures were not modified in the presence of T. arborea, ibogaine, or voacangine. However, sudden death was observed in mice treated with T. arborea extract at 100 mg/kg, i.p., combined with PTZ. Because T. arborea extract (100 mg/kg, i.p.) and ibogaine (30 mg/kg, i.p.), but not voacangine (30 mg/kg, i.p.), induced paroxysmal activity in the EEG, both were explored in the presence of a serotonin 5-HT1A receptor antagonist (WAY100635, 1 mg/kg, i.p.). The antagonist abolished the paroxysmal activity provoked by T. arborea (100 mg/kg, i.p.) but not that observed with ibogaine, corroborating the participation of serotonin neurotransmission in the T. arborea effects. In conclusion, high doses of the T. arborea extract induced abnormal EEG activity due in part to the presence of ibogaine and involving serotonin 5-HT1A receptor participation. Nevertheless, other possible constituents and mechanisms might participate in this complex excitatory activity that would be interesting to explore in future studies.

Temporally irregular electrical stimulation to the epileptogenic focus delays epileptogenesis in rats.

BACKGROUND: Variation in the temporal patterns of electrical pulses in stimulation trains has opened a new field of opportunity for the treatment of neurological disorders, such as pharmacoresistant temporal lobe epilepsy. Whether this novel type of stimulation affects epileptogenesis remains to be investigated. OBJECTIVE: The purpose of this study was to analyze the effects of temporally irregular deep brain stimulation on kindling-induced epileptogenesis in rats. METHODS: Temporally irregular deep brain stimulation was delivered at different times with respect to the kindling stimulation. Behavioral and electrographic changes on kindling acquisition were compared with a control group and a temporally regular deep brain stimulation-treated group. The propagation of epileptiform activity was analyzed with wavelet cross-correlation analysis, and interictal epileptiform discharge ratios were obtained. RESULTS: Temporally irregular deep brain stimulation delivered in the epileptogenic focus during the interictal period shortened the daily afterdischarge duration, slowed the progression of seizure stages, diminished the generalized seizure duration and interfered with the propagation of epileptiform activity from the seizure onset zone to the ipsi- and contralateral motor cortex. We also found a negative correlation between seizure severity and interictal epileptiform discharges in rats stimulated with temporally irregular deep brain stimulation. CONCLUSION: These results provide evidence that temporally irregular deep brain stimulation interferes with the establishment of epilepsy by delaying epileptogenesis by almost twice as long in kindling animals. Thus, temporally irregular deep brain stimulation could be a preventive approach against epilepsy.

Transcranial focal electrical stimulation via concentric ring electrodes in freely moving cats: Antiepileptogenic and postictal effects.

Transcranial focal electrical stimulation (TFS) via tripolar concentric ring electrodes (TCRE), tripolar TFS, is proposed to treat pharmacoresistant epilepsy. We determined the effect of tripolar TFS on electrical amygdaloid kindling (AK) in freely moving cats. Fifteen cats were bilaterally implanted with electrodes in the amygdala (AM) and prefrontal cortex and assigned to three groups: the control group, which only received AK; the tripolar TFS before AK group, in which TCREs were placed over the vertex and tripolar TFS (300 Hz, 200 µs biphasic equal charge, square pulses) was delivered for 40 min just prior to AK; and the tripolar TFS after AK group, in which the TCREs were placed over the temporal bone ipsilateral to the kindled AM, while tripolar TFS was administered for 2 min just after AK onset for 40 days, and, thereafter, only AK was applied. AK was applied daily until all animals reached kindling stage VI. A three concentric spheres finite element cat head model was developed to analyze the electric fields caused by tripolar TFS. Tripolar TFS after AK inhibited kindling development. Animals with tripolar TFS after AK remained at the focal seizure stages for 20 days after tripolar TFS cessation and required 80.0 ±â€¯15.42 AK stimulations to reach stage VI, significantly higher than TFS before AK, and control (P < .001). Tripolar TFS before AK did not show signs of protection against epileptogenesis. The finite modeling of tripolar TFS showed that the electric field is >0.3 mV/mm at depths less than approximately 12.6 mm in the cat brain, which should be strong enough to alter brain activity. In conclusion, tripolar TFS applied via a TCRE over the ipsilateral temporal area significantly delayed AK. This taken together with other reports of tripolar TFS aborting seizures in acute seizure models suggests that tripolar TFS is a promising new modality that should be considered for further testing.

Effects of High- and Low-Frequency Stimulation of the Thalamic Reticular Nucleus on Pentylentetrazole-Induced Seizures in Rats.

RATIONALE: The use of electrical stimulation therapy to treat epilepsy is currently being studied in experimental animals and patients. Our study was designed to evaluate the effects of electrical stimulation applied in the thalamic reticular nucleus (TRN) on the development of pentylentetrazole-induced seizures. MATERIALS AND METHODS: Experiments were performed using male Wistar rats with electrodes stereotaxically implanted in the left TRN. Epidural EEG recording screws were implanted in the motor cortex for EEG recording. The rats were classified in seven groups: one sham group, four groups receiving either high- or low-frequency preemptive stimulation for either 10 or 60 minutes, and two groups receiving either high- or low-frequency responsive stimulation for ten minutes. All animals received a single dose of pentylentetrazole throughout five days. EEG recordings were obtained from the cortex and were evaluated to assess ictal behavior more than 45 to 90 minutes. RESULTS: Ten minutes of preemptive high-frequency stimulation in the TRN induced a significant decrease in seizure severity compared to 60 minutes of preemptive stimulation and ten minutes of responsive stimulation. Additionally, ten minutes of preemptive high-frequency stimulation protected against death as aftereffect of status epilepticus. The spike-wave complex frequency was not modified. CONCLUSIONS: These data could contribute to the characterization of the TRN in mediating the initiation and spreading of seizure activity and provide preclinical support for optimal parameters to use to obtain beneficial effects against convulsive activity.

Justicia spicigera Schltdl. and kaempferitrin as potential anticonvulsant natural products.

Justicia spicigera Schltdl. is a vegetal species traditionally used to control epilepsy, but scientific evidence is required to reinforce this activity. The aim of the study was to evaluate the anticonvulsant-like activity of J. spicigera aqueous extract (JsAE) and a bioactive compound. JsAE was assessed in a dose-response manner (30, 100 and 1000mg/kg, i.p.) using the pentylenetetrazol (PTZ)-induced seizures and maximal electroshock seizure (MES) test in mice in comparison to ethosuximide (ETX, reference drug 100mg/kg, i.p.) or phenytoin (25mg/kg, i.p.), respectively. Then a significant dosage (1000mg/kg, i.p.) was chosen to examine electrographic activity (EEG) in rats. Treatment groups were compared to the vehicle and ETX in the convulsive behavior alone or simultaneous to EEG after PTZ-induced seizures (80 or 35mg/kg, i.p., mice or rats). Kaempferitrin (a flavonoid of JsAE) and ETX were administered via intracerebroventricular (i.c.v, 4th ventricle, 1µg/µL) and tested in the presence of PTZ in rats. Results confirmed that JsAE delayed the onset of seizures and reduced frequency of tonic convulsion and mortality in mice. JsAE or kaempferitrin also decreased the EEG spikes frequency and amplitude in a similar manner than EXT in rats. In conclusion, these preliminary data give evidence of the potential of J. spicigera as possible anticonvulsant as recommended in folk medicine for treating epilepsy, where kaempferitrin is suggested as a partial responsible bioactive compound.

Effect of vagus nerve stimulation on electrical kindling in different stages of seizure severity in freely moving cats.

Vagus nerve stimulation (VNS) is an adjunctive therapy for treating pharmacoresistant epilepsy. The present study analyze the effect of VNS on the epileptic activity of amygdala kindling (AK) in different seizure severity stages in freely moving cats. Fourteen adult male cats were used and were stereotaxically implanted in both amygdalae, in thalamic reticular nuclei and in prefrontal cortices. AK was developed by the application of 60Hz pulse trains that were one second in duration. VNS was applied the following day after the first stages were reached. This stimulation consisted of 10 pulse trains in the one-hour period (1min on/5min off) prior to AK. AK stimulation continued until all animals reached stage VI. The behavioral changes induced by VNS were transient and bearable. The animals showed relaxation of the nictitating membrane, ipsilateral anisocoria, swallowing and licking. Intermittent VNS application in stage I induced a delay in AK progression. The effect of VNS on the amygdala afterdischarge duration (AD) did not change progressively. VNS in stages II, III, and IV does not have an inhibitory effect on AK, and the AD further exhibited a progressive development. At the end of the generalized seizures, the animals presented with synchronized bilateral discharges of the spike-wave type (3Hz) and a behavioral "staring spell". Our results show that VNS applied during the different stages of seizure severity exerts an anti-epileptogenic effect in stage I but no anti-epileptogenic effect in stages II, III, and IV. These results suggest that VNS applied at stage I of kindling induces a delay of generalized convulsive activity.

Electroencephalographic activity in neonatal ventral hippocampus lesion in adult rats.

A neonatal ventral hippocampal lesion (NVHL) in rats has been commonly used as a neurodevelopmental model to mimic schizophrenia-like behaviors. Recently, we reported that NVHL resulted in dendritic retraction and spine loss in pyramidal neurons of the prefrontal cortex (PFC). In addition, the hippocampus and PFC are important structures in the regulation of the electroencephalographic (EEG) activity. Patients with PFC lesions show deficits in the EEG activity. This study aimed to determine whether the EEG activity was altered in NVHL rats. In addition, we also analyzed the locomotor activity induced by a novel environment and exploratory behavior using the hole-board test. Consistent with the behavioral findings, the EEG analysis of the cortical regions showed that the NVHL rats displayed a lower power in cortical bands. At 1-8 Hz, 9-14 Hz, and 15-30 Hz bands, our findings showed a decrease in the absolute power of the parietal and occipital cortices recordings. In addition, the NVHL rats also showed a reduction in the exploratory behavior tested using the hole-board test. In conclusion, this study demonstrated that the EEG activity was reduced in adult NVHL rats and suggests that this may play a role in the behavioral changes observed in this neurodevelopmental model of schizophrenia.

Behavioral characteristics, associative learning capabilities, and dynamic association mapping in an animal model of cerebellar degeneration.

Young adult heterozygous Lurcher mice constitute an excellent model for studying the role of the cerebellar cortex in motor performance-including the acquisition of new motor abilities-because of the early postnatal degeneration of almost all of their Purkinje and granular cells. Wild-type and Lurcher mice were classically conditioned for eyelid responses using a delay paradigm with or without an electrolytic lesion in the interpositus nucleus. Although the late component of electrically evoked blink reflexes was smaller in amplitude and had a longer latency in Lurcher mice than that in controls, the two groups of animals presented similar acquisition curves for eyeblink conditioning. The lesion of the interpositus nucleus affected both groups of animals equally for the generation of reflex and conditioned eyelid responses. Furthermore, we recorded the multiunitary activity at the red and interpositus nuclei during the same type of associative learning. In both nuclei, the neural firing activity lagged the beginning of the conditioned response (determined by orbicularis oculi muscle response). Although red nucleus neurons and muscle activities presented a clear functional coupling (strong correlation and low asymmetry) across conditioning, the coupling between interpositus neurons and either red nucleus neurons or muscle activities was slightly significant (weak correlation and high asymmetry). Lurcher mice presented a nonlinear coupling (high asymmetry) between red nucleus neurons and muscle activities, with an evident compensatory adjustment in the correlation of firing between interpositus and red nuclei neurons (a coupling with low asymmetry), aimed probably at compensating the absence of cerebellar cortical neurons.

Preemptive effect of nucleus of the solitary tract stimulation on amygdaloid kindling in freely moving cats.

PURPOSE: The nucleus of the solitary tract (NTS) is a primary site where vagal afferents terminate. The aim of this study was to analyze the preemptive effect of NTS electrical stimulation on daily amygdaloid kindling (AK) in freely moving cats. METHODS: Seven adult male cats were used. Bipolar electrodes were stereotaxically implanted into both amygdalae, lateral geniculate bodies, hippocampi, and prefrontal cortices. In addition, a bipolar stainless steel electrode was implanted in the left NTS. Cats were recorded under the following experimental conditions: The NTS was stimulated for 6 days before the initiation of AK (1 min on/5 min off, 1 h total). AK was performed by stimulating the amygdala every 24 h (1 s, 60 Hz, 1 ms) until behavioral stage VI was reached. RESULTS: The number of stimulations to reach stage VI in control animals was 23.4 +/- 3.7, in lateral tegmental field (LTF) animals was 17.0 +/- 2.1 days. Animals subjected to preemptive NTS stimulation showed a significant increase (53.8 +/- 5.9). In addition, behavioral development was retarded, with an increase in the number of stimulations required to reach stage III. In this group, overall kindling development was delayed, and amygdaloid afterdischarge duration did not show a progressive increase as was observed in the control group. DISCUSSION: Our results indicate that preemptive NTS electrical stimulation interferes with epileptogenesis. This anticonvulsive effect could be related to the activation of certain structures that inhibit seizure development. Therefore, results suggest that NTS mediates the anticonvulsive effect of vagus nerve stimulation.

Effects of electrical stimulation of the vagus nerve on the development of visual habituation in the cat.

The vagus nerve participates in the control and regulation of important autonomous functions, emotional tasks, and neural activity. Electrical vagus nerve stimulation (VNS) is an approved procedure for the treatment of refractory epilepsy in humans. VNS has also been shown to improve mood complaints and cognitive function in both human patients and animals. Thus, the purpose of this study was to analyse and describe the effects of VNS on the development and establishment of sensory habituation and electrographic activity of the visual pathway in freely moving cats. Six cats had implants placed in the optic chiasm (OC), lateral geniculate body (LGB), mesencephalic reticular formation (MRF), primary visual cortex (VC) of the left hemisphere, and left vagus nerve. Immediately after surgery, all cats presented anisocoria and relaxation of the left nictitant membrane. Also showed vegetative-type responses such as myosis, licking, and swallowing during VNS. Animals were then subjected to repeated luminous stimuli at intervals of 1 and 3s to cause habituation. The effect of VNS on the frequency and latency of the habituation episodes and the electrographic changes in the registered brain structures were analysed. Latency analysis showed that VNS delayed the first habituation episode. VNS had transitory effects on the neural activity of the primary visual pathway structures, which caused a small but measurable delay in the establishment of habituation. In conclusion, VNS interferes with the development and establishment of visual habituation, an elementary form of non-associative learning, in freely moving cats.

Long-term changes in sleep and electroencephalographic activity by chronic vagus nerve stimulation in cats.

We previously reported the effect of vagus nerve electrical stimulation (VNS) on sleep and behavior in cats. The aim of the present study is to analyze the long-term effects of VNS on the electroencephalographic (EEG) power spectrum and on the different stages of the sleep-wakefulness cycle in the freely moving cat. To achieve this, six male cats were implanted with electrodes on the left vagal nerve and submitted to 15 rounds of 23 h continuous sleep recordings in three categories: baseline (BL), VNS and post-stimulus recording (PSR). The following parameters were analyzed: EEG power spectrum, total time and number of sleep phases, ponto-geniculo-occipital (PGO) wave density of the rapid eye movement (REM) sleep, and the number of times the narcoleptic reflex was present (sudden transition from wakefulness to REM sleep). Significant changes were detected, such as an enhancement of slow-wave sleep (SWS) stage II; a power increase in the bands corresponding to sleep spindles (8-14 Hz) and delta waves (1-4 Hz) with VNS and PSR; an increase in the total time, number of stages, and density of PGO wave in REM sleep with VNS; a decrease of wakefulness in PSR, and the eventual appearance of the narcoleptic reflex with VNS. The results show that the effect of the VNS changes during different stages of the sleep-wakefulness cycle. In REM sleep, the effect was present only during VNS, while the SWS II was affected beyond VNS periods. This suggests that ponto-medullar and thalamic mechanisms of slow EEG activity may be due to plastic changes elicited by vagal stimulation.

Effect of electrical stimulation of the nucleus of the solitary tract on the development of electrical amygdaloid kindling in the cat.

PURPOSE: This work analyzed the effect of electrical stimulation of the nucleus of the solitary tract (NTS) on the development of electrical amygdaloid kindling (AK) in freely moving cats. METHODS: Nine male adult cats with implanted electrodes in both amygdalae (basolateral nucleus), both lateral geniculate bodies, left NTS, and both prefrontal cortices were used. Electromyogram and electrooculogram also were recorded. The AK was performed every 24 h (1-s train, 1-ms pulses, 60 Hz, 300-600 microA). The NTS was stimulated previously for 1 min (0.5-ms pulses, 30 Hz, 150-300 microA), just before the AK at 10:00 a.m., and then every 60 min, 4 times, from 11:00 a.m. to 2:00 p.m. On different days, all NTS stimulation was suspended, and AK was continued until stage VI kindling was reached. RESULTS: Behavioral changes produced by the stimulation of the NTS were blinking, immobility periods with upward sight, licking, and swallowing. Animals with simultaneous stimulation of NTS and AK did not reach stage VI, remaining in behavioral stages I-III. Stage VI was reached after NTS stimulation was intentionally suspended. The amplitude, duration, and the propagation of the amygdaloid afterdischarge did not exhibit progressive evolution during NTS stimulation. A regression analysis was performed between the number of days with only AK stimulation and days with simultaneous NTS stimulation, which showed a positive correlation (values of r = 0.84). CONCLUSIONS: Our results suggest that NTS stimulation interferes with the development of convulsive evolution and secondary generalization. This delay effect may be due to the activation of the locus ceruleus and some areas of the midbrain reticular formation, among other structures, which has been demonstrated to inhibit experimental convulsive seizures.

Chronic stimulation of the cat vagus nerve: effect on sleep and behavior.

The effect of electrical vagus nerve stimulation (VNS) on sleep and behavior was analyzed in freely moving cats. Eight cats were prepared for 23-h sleep recordings. The left vagus nerve of four of them was stimulated during 1 min, five times at 1-h intervals, for 5 days. The VNS induces: ipsilateral myosis, blinking, licking, abdominal contractions, upward gaze, swallowing, and eventually yawning and compulsive eating, as well as an increase of ponto-geniculate-occipital (PGO) wave density and of the number of stages and total amount of rapid eye movement (REM) sleep. Besides, there was a sudden transition from waking stage to REM sleep. The present results suggest that VNS modifies sleep in the cat. This effect could be explained by an activation of the areas involved in the physiological mechanisms of sleep.