Amygdala kindling differentially regulates the expression of the elements involved in TRH transmission.

Subthreshold electrical stimulation of the amygdala (kindling) activates neuronal pathways increasing the expression of several neuropeptides including thyrotropin releasing-hormone (TRH). Partial kindling enhances TRH expression and the activity or its inactivating ectoenzyme; once kindling is established (stage V), TRH and its mRNA levels are further increased but TRH-binding and pyroglutamyl aminopeptidase II (PPII) activity decreased in epileptogenic areas. To determine whether variations in TRH receptor binding or PPII activity are due to regulation of their synthesis, mRNA levels of TRH receptors (R1, R2) and PPII were semi-quantified by RT-PCR in amygdala, frontal cortex and hippocampus of kindled rats sacrificed at stage II or V. Increased mRNA levels of PPII were found at stage II in amygdala and frontal cortex, and of pro-TRH and TRH-R2, in amygdala and hippocampus. At stage V, pro-TRH mRNA levels increased and those of PPII, decreased in the three regions; TRH-R2 mRNA levels diminished in amygdala and frontal cortex and of TRH-R1 only in amygdala. In situ hybridization analyses revealed, at stage II, enhanced TRH-R1 mRNA levels in dentate gyrus and amygdala while decreased in piriform cortex; those of TRH-R2 increased in amygdala, CA2, dentate gyrus, piriform cortex, thalamus and subiculum and of PPII, in CAs and piriform cortex. In contrast, at stage V decreased expression of TRH-R1 occurred in amygdala, CA2/3, dentate gyrus and piriform cortex; of TRH-R2 in CA2, thalamus and piriform cortex, and of PPII in CA2, and amygdala. The magnitude of changes differed between ipsi and contralateral side. These results support a trans-synaptic modulation of all elements involved in TRH transmission in conditions that stimulate the activity of TRHergic neurons. They show that reported changes in PPII activity or TRH-binding caused by kindling relate to regulation of the expression of TRH receptors and degrading enzyme.

Phasic activity of the basolateral amygdala, cingulate gyrus, and hippocampus during REM sleep in the cat.

We analyzed the electrical activity of the basolateral amygdala (BLA), anterior and posterior regions of the cingulate gyrus (A-CG and P-CG), the dorsal hippocampus (DH), the anterior ventral thalamic nucleus (AVTN), and the sensory motor cortex during the rapid eye movements and ponto-geniculo-occipital (PGO) activity of REM sleep in cats in chronic preparation. Polygraphic recordings and computational perievent averages using the phasic contractions of the lateral rectus muscle (LR) of the eyeball as the triggering signal of the analysis were performed. We observed biphasic potentials (200-300 ms) of variable amplitude, related to the phasic phenomena of REM sleep, in the BLA, A-CG, P-CG, DH, and AVTN. The latencies of the potentials of these regions were always greater than those of the geniculate PGO activities. We propose that the recorded limbic potentials resulted from propagation of PGO activity and that this phenomenon may reflect the limbic structure of the hallucinatory, vegetative, and emotional components of REM sleep.

Sleep alterations following total cerebellectomy in cats.

Polygraphic sleep studies were conducted in six cats just before cerebellectomy and 3 and 10 days after the operation. These studies were continued in the four surviving animals 30, 100, 200, 300, and 315 days days post-operatively. The findings confirmed the existence of two postoperative phases correlated with the degeneration of brainstem structures: an initial period (day 3) was characterized by a significant increase in wakefulness; a second, later period (days 10 and 30) was distinguished by numerous slow waves and sleep spindles in the electrocorticogram. There was a stable increase in the amplitude and density of rapid eye movements, perhaps reflecting the ataxia evident during the waking state after cerebellectomy. At day 3, there was a significant decrease in the duration of paradoxical sleep (PS) periods, followed by a significant increase at day 10 that continued to the end of the study. The number of PS states tended to decrease and the PS latency tended to increase in the long-term survivors. All other sleep parameters appeared to normalize by day 100. These findings suggest that the cerebellum plays a modulatory role with respect to the pontine structures responsible for the generation of phasic activity during PS.

Effects of clonidine in narcolepsy.

The antihypertensive drug clonidine was given in an open trial to two treatment-resistant (psychostimulants and tricyclic antidepressants) narcoleptic patients. When given acutely, clonidine suppressed REM sleep. However, patients became tolerant after repeated doses but did not lose the drug's beneficial clinical effects. This suggests that REM suppression may not be necessary for improvement in narcolepsy. Assessments of both clinical and polysomnographic variables before and after the trial indicate that clonidine may have a place in the treatment of some patients with narcolepsy.

Effects of 1 week administration of two benzodiazepines on the sleep and early daytime performance of normal subjects.

This study analyzed the effects of 1 week administration of alprazolam (AL; 0.25 mg), lorazepam (LO; 1 mg) and placebo (PL) on sleep as well as their residual effects on attention upon awakening. Under a crossed, double-blind design, six healthy male volunteer subjects between 19 and 30 years of age were studied. After two habituation sessions and a control session, each substance was given orally, twice a day for 7 days, with a 1-week washout period between administrations. At the end of each administration period, sleep studies were conducted from 2300 to 0700 hours. Evaluation of attention was carried out by means of a simple visuomotor reaction time (RT) task, and a time estimation (TE) task, that started at 0700 hours, lasting 1 h. Neither drug significantly affected any sleep variable. Both benzodiazepines tended to increase RT, but only LO did so significantly at the beginning of the attention test. No significant changes in predictive and failure responses during the RT task were produced by either drug. Also, no significant changes were observed in the TE. Even though only LO produced a significant increase of RT at the selected doses and with 1 week administration, it is suggested that both benzodiazepines could have residual effects on attention.

Penicillin-G induced interictal activity increases both opioid peptide tissue content and in vitro release in the rat brain.

Penicillin-G has been used as a common agent to produce epileptic foci and interictal activity. The development of the interictal spikes has been associated with enhanced inhibitory effects. There is evidence that the opioid peptides play an important role in the production of some transient postictal behaviors. In order to test whether enkephalins are involved during the interictal activity, we analyzed immunoreactive met- and leu-enkephalin content and their release in vitro, after the injection of 50 IU of penicillin-G into the left amygdala. Male Wistar rats were injected once daily for 5 days, and sacrificed by decapitation (15 min after the penicillin-G infusion) on the fifth day. The rats were divided into two groups: 1. In one group we analyzed the tissue content of enkephalins in hypothalamus, hippocampus, amygdala, striatum and cerebral cortext. 2. The second group was used for the assessment of the in vitro release of enkephalins from amygdala slices. In the amygdala, the drug treatment produced an increase in the tissue content of IR-ME. No changes occurred in the other structures. The content of IR-Leu-enkephalin increased in all structures analyzed except the cerebral cortex. In vitro release of both enkephalins increased in drug treated animals. These results suggest that the enkephalins could be involved in postictal mechanisms, as a result of repetitive interictal spiking.

Habituation and dehabituation of the spinal polysynaptic reflex responses: modification by naloxone and opiates and their anatomical correlates.

The sustained inhibitory action of spinal endorphins could be responsible for the habituation of polysynaptic responses in the spinal cord. To test this hypothesis, acute spinalized unanesthetized cats (decerebrated and curarized) were used. Sural nerve electrical stimulation (0.2 Hz) was provided and a progressive decrease in the reflex response was found. Conversely, the field potential (lamina V) progressively increased during stimulation, reaching its maximum amplitude when ventral root response showed maximum habituation. The administration of naloxone (0.8-10.0 mg/kg) produced dehabituation or prevented habituation. The immunohistological results showed leu-enkephalin-like immunoreactive dot-like structures in close proximity to neurons of laminae VII, VIII and IX in the lumbo-sacral segment of the spinal cord. Our results suggest an involvement of opioid peptides in the habituation process.

Changes in TRH and its degrading enzyme pyroglutamyl peptidase II, during the development of amygdaloid kindling.

Pyroglutamyl peptidase II (PPII) is a neuronal ectoenzyme responsible for thyrotropin releasing hormone (TRH) degradation at the synaptic cleft. PPII, heterogeneously distributed in different brain regions and adenohypophysis, is regulated under various endocrine conditions where TRH is involved in thyrotropin or prolactin regulation but only at the adenohypophyseal level. TRH can downregulate PPII activity in cultured adenohypophyseal cells. TRH present in extrahypothalamic brain areas has been postulated to serve as a neuromodulator and levels of this peptide increase in amygdala, hippocampus and cortex after electrical stimulation (kindling or electroshock). To study whether brain PPII could be regulated in conditions that stimulate TRHergic neurons, TRH and PPII activity were determined during the development of amygdaloid kindling in the rat. TRH levels increased from stage II to V in amygdala and hippocampus in the ipsi- and contralateral side to stimulation. In n. accumbens a decrease, compared to sham was observed at stage II, but levels raised through stage V. In contrast, PPII activity was increased at stage II, in amygdala of both sides and in hipppocampus, frontal cortex, n. accumbens and hypothalamus of the contralateral side; levels decreased at stage V to sham values in most structures (except amygdala and hippocampus where the activity was 30% below controls). These results suggest that PPII activity in the central nervous system can be regulated in conditions known to affect TRHergic neurons.

Amygdaloid kindling enhances the enkephalin content in the rat brain.

Established amygdaloid kindling causes an increase in the immunoassayable content of both Leuenkephalin and Met-enkephalin in the rat brain. Control and sham-operated (electrode implanted but not stimulated) rats do not show statistically significant differences in brain enkephalin content, while kindled rats show a 40% enkephalin increase in both hemispheres. The present finding is in agreement with several lines of evidence and suggest that enkephalins may play a role in epileptic seizures.

Brain content of leu5- and met5-enkephalin changes independently during the development of kindling in the rat.

Brain content of leucine-enkephalin and methionine-enkephalin changes independently during kindling of the amygdala. Both peptides were measured after 4, 8, 15 and 21 days of stimulation. Leu-enkephalin showed a progressive increase during the kindling: the results on the 4th day did not differ significantly from the controls, whereas those on the 8th day displayed an increase only in the stimulated left hemisphere and those on the 15th day showed an increase in both hemispheres. This increase was also seen after 21 days of stimulation. In contrast, Met-enkephalin was not modified during the early stages of kindling, but was found to be increased after the animals had presented five or more generalized seizures. These results show that Leu-enkephalin is related to the development of kindling, whereas Met-enkephalin levels change only as a consequence of the generalized seizures.

Amygdaloid kindling during rapid eye movement (REM) sleep in cats.

Development of amygdaloid kindling was analyzed during REM sleep and during wakefulness. Daily evolution of electrographic and behavioral changes was significantly delayed in REM kindled rats. The number of kindling trials required to reach the first generalized convulsive seizure was also significantly increased in comparison with awake kindled animals. Changes in sleep organization were measured under REM kindling conditions. A significant increase in total sleep time and in the percentage of light slow-wave sleep was found during the kindling process. No significant sleep changes were observed in REM-established kindling. REM inhibitory influence over epileptogenesis is discussed.

Naloxone effects on the visual evoked potentials recorded from the main and accessory visual pathways of the cat.

1. The effects produced by repetitive i.v. administration of naloxone (1, 2 or 4 mg/kg) on the visual evoked potentials (VEPs) recorded along the main and accessory visual pathways were investigated in a modified "encéphale isolé" cat preparation. 2. Naloxone provoked a progressive amplitude enhancement and latency reduction of some components, depending on the structure analyzed, the dose used and the number of administrations applied. Electroretinogram (ERG) and N1-P1 VEP components of optic chiasm (OCh), lateral geniculate body (LGB) and visual cortex (VC) did not present significant changes. 3. Late-latency components (more than 200 msec) appeared in the VEPs of LGB and VC, mainly when 4 mg/kg were used. 4. Our results suggest that endogenous opioids have a modulatory role in the processing of sensory information at different levels of the visual system.

Repeated penicillin-induced amygdala epileptic focus in freely moving cats. EEG, polysomnographic (23-h recording), and brain mapping study.

The effect of repeated Na-penicillin (PCN) microinjections in the temporal lobe amygdala (AM) of free-moving cats was investigated in order to establish if kindling epileptogenesis is possible with this procedure. The cortical propagation of the PCN-induced post-discharge in AM and the sequence of behavioral changes induced by PCN were similar to those of AM electrical kindling. Nevertheless, the epileptogenic effect of PCN had a different evolution from that of electrical kindling, since some PCN habituation was observed after several doses. Repeated microinjections of PCN did not produce lasting alterations in sleep onset and organization. The only mild changes recorded in the 23 h following PCN microinjections were an increased latency of the first rapid eye movement (REM) sleep episode, a SWS II total time and percentage increase, and, with the highest PCN doses, a not very significant diminution of REM sleep total time. Another finding was the occurrence of REM sleep ponto-geniculo-occipital (PGO) waves, coinciding with a depression of the frequency and amplitude of interictal amygdaloid and cortical spikes. The results showed that a microinjection of PCN in the AM produced a reliable model of interictal spikes, paroxysms and generalized convulsive seizures. Nevertheless, long lasting kindling effect was not observed.

EEG frequency and time domain mapping study of the cortical projections of temporal lobe amygdala afterdischarge during kindling in the cat.

EEG frequency and time domain color maps were computed during amygdala kindling in cats. The pattern of the amygdala afterdischarge (AM/AD) propagation to the cortex was assessed as kindling evolved. Our results show that the AM/AD has 4 components that coincide with the activation of certain cortical areas during specific behavioral stages. The pattern of the cortical projection follows an asymmetrical temporo-fronto-occipital direction, the ipsilateral temporal lobe being the first activated zone, followed by the ipsilateral and contralateral prefrontal areas. The contralateral temporal activation is a late phenomenon. We conclude that the electrographic and behavioral manifestations of this model of complex partial epilepsy are asymmetrical during the whole process, including the convulsive stage.

Massed amygdaloid kindling in encéphale isolé cats: its facilitation by naloxone.

The effect of repetitive administration of naloxone on the development of massed amygdaloid kindling in 'encéphale isolé' cats was studied. Electrical amygdaloid kindling was carried out with a 15 min inter-stimulus interval (ISI) in a control situation with intravenous (i.v.) naloxone administration (2, 4, and 8 mg/kg), 5 min prior to amygdaloid stimulation. It was found that it was possible to complete the amygdaloid kindling process in the encéphale isolé preparation reaching generalized electrographic tonic-clonic self-sustained seizures. The enhancement of the duration, frequency, and propagation of the after-discharge (AD) was accentuated by naloxone which also induced a progressive amplitude increment of the first potential evoked by the onset of the tetanus. The number of trials needed to achieve seizure generalization was reduced in dose-dependent manner by naloxone. The ability of naloxone to accelerate the development of amygdaloid kindling may be related to an inhibitory role of opioid peptides in this process.

The assessment of residual effects of a single dose of diazepam on visually-defined EEG patterns.

The aim of this single-blind study was to evaluate the residual effects of a 10-mg dose of diazepam on cortical activation 11 h after oral intake. The electroencephalographic segments (from O1-O2) delimited by a sequence of photic stimuli presented every 10 sec during a simple reaction-time task (36 min duration) were arbitrarily classified into nine cerebral patterns (EEGP). EEGP segment classifications were grouped into six peri-stimulus transitions expressed in percentages: alpha-blockade; alpha-persistence; beta-persistence; alpha-induction; activation and deactivation. A sample of 42 young healthy university students (21 females and 21 males) each underwent three counterbalanced experimental conditions (control, placebo and diazepam). Diazepam affected all the subjects, although the women showed a greater number of EEGP transitions which indicated deactivation, than did the men. The results show that this type of visual EEG analysis is a useful technique for detecting the residual effects of benzodiazepines.

[Analysis of eye disease and adaptation of visual aids in low vision patients: review of 1,000 cases]. / Análisis de la patología ocular y de la adaptación de ayudas visuales en pacientes afectos de baja visión: revisión de 1.000 casos.

PURPOSE: To study the success of visual rehabilitation in a group of 1,000 patients with low vision. METHOD: Clinical data on visual rehabilitation was studied in 1,000 subsequent patients suffering from visual impairment. Study focused on ocular disease, improvement in visual acuity and successful use of visual aids. A statistical analysis of results is presented. RESULTS: 25 cases dropped out due to issues in primary diagnosis. Remaining 975 patients were assigned to 9 groups: age-related macular degeneration (339) diabetic retinopathy (264 cases), myopic maculopathy (195 cases), glaucoma (96 cases), congenital maculopathy (39 cases), retinal detachment (12 patients), retinitis pigmentosa (13 cases), macular pucker (6 patients) and a miscellaneous group of 11 cases. The overall success in the improvement in visual acuity was 98% except for a group of patients with retinitis pigmentosa where a rate of only 46% success (p<0.01) was observed. 76% of cases finally accepted visual rehabilitation aids. CONCLUSIONS: The usefulness of visual rehabilitation in low vision patients is confirmed, with the exception of retinitis pigmentosa cases, probably due to features of the disease itself. The design of visual aids should be improved in order to benefit a greater number of patients.