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1.
Cephalalgia ; 26(8): 973-82, 2006 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-16886934

RESUMO

This study aimed to examine penetration of the blind in a randomized, placebo-controlled trial. Neurologists' ratings of improvement and medication side-effects, participants' ratings of improvement and daily diary recordings of headaches were assessed along with participants' and neurologists' guesses about treatment group placement in participants who completed at least 3 months of treatment (N = 169). Despite blinding, treating neurologists successfully identified the medication condition for 82% of participants receiving medication only; trial participants accurately identified their medication condition when receiving active medication (77% of participants), but not when receiving placebo. Concurrent stress-management therapy reduced, but did not eliminate penetration of the blind. Irrespective of drug condition, when participants were improved they were judged to be on active medication and when unimproved they were judged to be on placebo. However, neurologists' ratings of improvement, participants' reports of improvement and daily headache recordings yielded equivalent outcomes. Penetration of the blind needs to be assessed, not assumed in clinical trials in headache. However, penetration of the blind did not produce a prodrug bias as has been asserted by critics. Better methods of assessing and quantifying blindness are needed.


Assuntos
Antidepressivos/uso terapêutico , Viés , Método Duplo-Cego , Garantia da Qualidade dos Cuidados de Saúde/métodos , Ensaios Clínicos Controlados Aleatórios como Assunto/estatística & dados numéricos , Cefaleia do Tipo Tensional/tratamento farmacológico , Cefaleia do Tipo Tensional/epidemiologia , Adolescente , Adulto , Idoso , Fatores de Confusão Epidemiológicos , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Ohio/epidemiologia , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Resultado do Tratamento
2.
JAMA ; 285(17): 2208-15, 2001 May 02.
Artigo em Inglês | MEDLINE | ID: mdl-11325322

RESUMO

CONTEXT: Chronic tension-type headaches are characterized by near-daily headaches and often are difficult to manage in primary practice. Behavioral and pharmacological therapies each appear modestly effective, but data are lacking on their separate and combined effects. OBJECTIVE: To evaluate the clinical efficacy of behavioral and pharmacological therapies, singly and combined, for chronic tension-type headaches. DESIGN AND SETTING: Randomized placebo-controlled trial conducted from August 1995 to January 1998 at 2 outpatient sites in Ohio. PARTICIPANTS: Two hundred three adults (mean age, 37 years; 76% women) with diagnosis of chronic tension-type headaches (mean, 26 headache d/mo). INTERVENTIONS: Participants were randomly assigned to receive tricyclic antidepressant (amitriptyline hydrochloride, up to 100 mg/d, or nortriptyline hydrochloride, up to 75 mg/d) medication (n = 53), placebo (n = 48), stress management (eg, relaxation, cognitive coping) therapy (3 sessions and 2 telephone contacts) plus placebo (n = 49), or stress management therapy plus antidepressant medication (n = 53). MAIN OUTCOME MEASURES: Monthly headache index scores calculated as the mean of pain ratings (0-10 scale) recorded by participants in a daily diary 4 times per day; number of days per month with at least moderate pain (pain rating >/=5), analgesic medication use, and Headache Disability Inventory scores, compared by intervention group. RESULTS: Tricyclic antidepressant medication and stress management therapy each produced larger reductions in headache activity, analgesic medication use, and headache-related disability than placebo, but antidepressant medication yielded more rapid improvements in headache activity. Combined therapy was more likely to produce clinically significant (>/=50%) reductions in headache index scores (64% of participants) than antidepressant medication (38% of participants; P =.006), stress management therapy (35%; P =.003), or placebo (29%; P =.001). On other measures the combined therapy and its 2 component therapies produced similar outcomes. CONCLUSIONS: Our results indicate that antidepressant medication and stress management therapy are each modestly effective in treating chronic tension-type headaches. Combined therapy may improve outcome relative to monotherapy.


Assuntos
Antidepressivos Tricíclicos/uso terapêutico , Terapia Comportamental , Cefaleia do Tipo Tensional/terapia , Adulto , Amitriptilina/uso terapêutico , Doença Crônica , Terapia Cognitivo-Comportamental , Terapia Combinada , Feminino , Humanos , Masculino , Nortriptilina/uso terapêutico , Terapia de Relaxamento , Estresse Psicológico/prevenção & controle
3.
Cephalalgia ; 20(7): 638-46, 2000 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-11128821

RESUMO

We examined pericranial muscle tenderness and abnormalities in the second exteroceptive suppression period (ES2) of the temporalis muscle in chronic tension-type headache (CTTH; n = 245) utilizing a blind design and methods to standardize the elicitation and scoring of these variables. No ES2 variable differed significantly between CTTH sufferers and controls (all tests, P>0.05). We found no evidence that CTTH sufferers with daily or near daily headaches, a mood or an anxiety disorder, or high levels of disability exhibit abnormal ES2 responses (all tests, P>0.05). CTTH sufferers were significantly more likely than controls to exhibit pervasive tenderness in pericranial muscles examined with standardized (500 g force) manual palpation (P<0.005). Female CTTH sufferers exhibited higher levels of pericranial muscle tenderness than male CTTH sufferers at the same level of headache activity (P<0.0001). Elevated pericranial muscle tenderness was associated with a comorbid anxiety disorder. These findings provide further evidence of pericranial hyperalgesia in CTTH and suggest this phenomenon deserves further study. Basic research that better elucidates the biological significance of the ES2 response and the factors that influence ES2 assessments appears necessary before this measure can be of use in clinical research.


Assuntos
Músculo Esquelético/fisiopatologia , Terminações Nervosas/fisiopatologia , Neurônios Aferentes/fisiologia , Cefaleia do Tipo Tensional/fisiopatologia , Adolescente , Adulto , Idoso , Doença Crônica , Avaliação da Deficiência , Feminino , Humanos , Hiperalgesia/etiologia , Hiperalgesia/fisiopatologia , Masculino , Prontuários Médicos , Pessoa de Meia-Idade , Dor/fisiopatologia , Psicofisiologia/métodos , Crânio , Cefaleia do Tipo Tensional/complicações , Cefaleia do Tipo Tensional/psicologia
4.
Headache ; 40(1): 3-16, 2000 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-10759896

RESUMO

OBJECTIVES: To examine the psychosocial correlates of chronic tension-type headache and the impact of chronic tension-type headache on work, social functioning, and well-being. METHODS: Two hundred forty-five patients (mean age = 37.0 years) with chronic tension-type headache as a primary presenting problem completed an assessment protocol as part of a larger treatment outcome study. The assessment included a structured diagnostic interview, the Medical Outcomes Study Short Form, Disability Days/Impairment Ratings, Recurrent Illness Impact Profile, Beck Depression Inventory, State-Trait Anxiety Inventory-Trait Form, Primary Care Evaluation for Mental Disorders, and the Hassles Scale Short Form. Comparisons were made with matched controls (N = 89) and, secondarily, with Medical Outcomes Study data for the general population, arthritis, and back problem samples. RESULTS: About two thirds of those with chronic tension-type headache recorded daily or near daily (> or =25 days per month) headaches with few (12%) recording headaches on less than 20 days per month. Despite the fact that patients reported that their headaches had occurred at approximately the present frequency for an average of 7 years, chronic tension-type headache sufferers were largely lapsed consulters (54% of subjects) or current consulters in primary care (81% of consulters). Significant impairments in functioning and well-being were evident in chronic tension-type headache and were captured by each of the assessment devices. Although headache-related disability days were reported by 74% of patients (mean = 7 days in previous 6 months), work or social functioning was severely impaired in only a small minority of patients. Sleep, energy level, and emotional well-being were frequently impaired with about one third of patients recording impairments in these areas on 10 or more days per month. Most patients with chronic tension-type headache continued to carry out daily life responsibilities when in pain, although role performance at times was clearly impaired by headaches and well-being was frequently impaired. Chronic tension-type headache sufferers were 3 to 15 times more likely than matched controls to receive a diagnosis of an anxiety or mood disorder with almost half of the patients exhibiting clinically significant levels of anxiety or depression. Affective distress and severity of headaches (Headache Index) were important determinants of headache impact/impairment. CONCLUSIONS: Chronic tension-type headache has a greater impact on individuals' lives than has generally been realized, with affective distress being an important correlate of impairment. If treatment is to remedy impairment in functioning, affective distress, as well as pain, thus needs to be addressed.


Assuntos
Qualidade de Vida , Cefaleia do Tipo Tensional/psicologia , Adolescente , Adulto , Idoso , Doença Crônica , Pessoas com Deficiência , Feminino , Humanos , Masculino , Transtornos Mentais/complicações , Pessoa de Meia-Idade , Testes Psicológicos , Cefaleia do Tipo Tensional/complicações
5.
J Consult Clin Psychol ; 63(2): 327-30, 1995 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-7751496

RESUMO

This article evaluated the ability of propranolol to enhance results achieved with relaxation-biofeedback training. Thirty-three patients were randomized to relaxation-biofeedback training alone (administered in a limited-contact treatment format), or to relaxation-biofeedback training accompanied by long-acting propranolol (with dosage individualized at 60, 120, or 180 mg/day). Concomitant propranolol therapy significantly enhanced the effectiveness of relaxation-biofeedback training when either daily headache recordings (79% vs. 54% reduction in migraine activity) or neurologist clinical evaluations (90% vs. 66% reduction) were used to assess treatment outcome. Concomitant propranolol therapy also yielded larger reductions in analgesic medication use and greater improvements of quality of life measures than relaxation-biofeedback training alone but was more frequently associated with side effects.


Assuntos
Biorretroalimentação Psicológica/efeitos dos fármacos , Transtornos de Enxaqueca/terapia , Propranolol/administração & dosagem , Terapia de Relaxamento , Temperatura Cutânea/efeitos dos fármacos , Adolescente , Adulto , Terapia Combinada , Relação Dose-Resposta a Droga , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Transtornos de Enxaqueca/psicologia , Resultado do Tratamento
6.
Am J Emerg Med ; 11(3): 251-2, 1993 May.
Artigo em Inglês | MEDLINE | ID: mdl-8489672

RESUMO

Numerous investigators have found that serum prolactin levels increase after tonic-clonic and partial complex seizures, but the effect of syncope on prolactin levels has been studied little. Serum prolactin levels were measured following unexpected syncopal attacks in patients seeking emergency treatment in a community hospital. Levels sampled 18 to 60 minutes after syncopal episodes were increased in 8 of 11 cases. Follow-up prolactin levels, measured 17 to 222 days later, were normal in all eight cases in which they were initially increased. Most subjects had concurrent illness. Although the current study does not clarify whether it was the syncope, the concurrent illness, or both that caused the prolactin elevations, it implies that measurement of this hormone will not help the clinician in distinguishing between seizures and syncopal attacks.


Assuntos
Prolactina/sangue , Síncope/sangue , Adolescente , Adulto , Idoso , Criança , Emergências , Feminino , Humanos , Masculino , Pessoa de Meia-Idade
8.
J Consult Clin Psychol ; 59(3): 387-93, 1991 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-2071723

RESUMO

Forty-one recurrent tension headache sufferers were randomly assigned to either cognitive-behavioral therapy (administered in a primarily home-based treatment protocol) or to amitriptyline therapy (with dosage individualized at 25, 50, or 75 mg/day). Cognitive-behavioral therapy and amitriptyline each yielded clinically significant improvements in headache activity, both when improvement was assessed with patient daily recordings (56% and 27% reduction in headache index, respectively), and when improvement was assessed with neurologist ratings of clinical improvement (94% and 69% of patients rated at least moderately improved, respectively). In instances where differences in treatment effectiveness were observed (headache index, somatic complaints, perceptions of control of headache activity), cognitive-behavioral therapy yielded somewhat more positive outcomes than did amitriptyline. Neither treatment, however, eliminated headache problems.


Assuntos
Amitriptilina/uso terapêutico , Terapia Cognitivo-Comportamental/métodos , Cefaleia/terapia , Adulto , Feminino , Cefaleia/tratamento farmacológico , Cefaleia/psicologia , Humanos , Masculino , Pessoa de Meia-Idade , Inventário de Personalidade , Estudos Prospectivos , Terapia de Relaxamento , Estresse Psicológico/complicações
9.
Headache ; 31(5): 333-40, 1991 May.
Artigo em Inglês | MEDLINE | ID: mdl-1830566

RESUMO

We used meta-analytic statistical techniques to synthesize findings from studies that evaluated propranolol HCI for the prevention of recurrent migraine (2,403 treated patients). The modal migraine sufferer treated in these studies was a female, about 37 years of age, who suffered from common (rather than classical) migraines and reported a 17-year history of problem migraines. The modal treatment was 160 mg. propranolol per day. Meta-analysis revealed that, on average, propranolol yielded a 44% reduction in migraine activity when daily headache recordings were used to assess treatment outcome, and a 65% reduction in migraine activity when less conservative measures (e.g., clinical ratings of improvement, global patient reports) were used. Meta-analysis thus revealed substantial support for short-term effectiveness of propranolol. However, little information was available concerning the long-term effectiveness of propranolol.


Assuntos
Transtornos de Enxaqueca/tratamento farmacológico , Propranolol/uso terapêutico , Adulto , Feminino , Humanos , Masculino , Metanálise como Assunto , Transtornos de Enxaqueca/fisiopatologia , Transtornos de Enxaqueca/prevenção & controle , Prognóstico , Propranolol/efeitos adversos , Recidiva
11.
Biofeedback Self Regul ; 14(4): 301-8, 1989 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-2698751

RESUMO

This report presents the first prospective comparison of the long-term maintenance of reductions in recurrent migraine headaches achieved with (abortive) pharmacological and nonpharmacological (combined relaxation training and thermal biofeedback training) treatments. Nineteen of 21 (90%) successfully treated patients (50% or greater reduction in headache activity) were contacted for follow-up evaluation 3 years later. Migraine sufferers who had been treated with ergotamine were less likely to still be relying on the treatment they had received and more likely to have additional medical treatment for their headaches and to be using prophylactic or narcotic medication than were migraine sufferers who had been treated with relaxation/biofeedback training. However, daily headache recordings revealed that patients in both treatment groups continued to show lower headache activity at 3-year follow-up than prior to treatment. Although preliminary, these findings raise the possibility that improvements achieved with nonpharmacological treatment are more likely to be maintained without additional treatment than are similar improvements achieved with abortive pharmacological treatment.


Assuntos
Biorretroalimentação Psicológica , Ergotamina/uso terapêutico , Transtornos de Enxaqueca/terapia , Adulto , Feminino , Seguimentos , Humanos , Masculino , Pessoa de Meia-Idade , Transtornos de Enxaqueca/tratamento farmacológico , Recidiva , Terapia de Relaxamento , Inquéritos e Questionários
12.
Headache ; 29(3): 148-53, 1989 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-2496052

RESUMO

Research suggests that approximately one half of recurrent headache sufferers fail to adhere properly to drug treatment regimens with as many as two thirds of patients failing to make optimal use of abortive medications such as ergotamine. In spite of these findings there are no controlled studies that have attempted to evaluate methods for improving adherence to drug regimens for the treatment of chronic headache disorders. In an initial effort to address this adherence problem thirty-four recurrent migraine sufferers were randomized to abortive therapy with ergotamine tartrate plus caffeine (standard abortive therapy) or to standard abortive therapy accompanied by a brief educational intervention designed to facilitate the migraine sufferer's effective use of ergotamine. Patients who received the adjunctive educational intervention attempted to abort a greater percentage of their migraine attacks (70% vs 40%) and showed larger reduction in headache activity (e.g., 40% vs 26% reduction in month two of treatment). However, patients in both treatment groups used similar amounts of abortive medication when attempting to abort a migraine attack and showed similar reductions in analgesic medication use with abortive therapy. There results suggest that brief educational interventions designed to address the problem of patient adherence may yield significant improvements in standard therapies. We argue that such educational interventions deserve more attention in the headache treatment literature than they have received to date.


Assuntos
Cafeína/administração & dosagem , Ergotaminas/administração & dosagem , Transtornos de Enxaqueca/tratamento farmacológico , Cooperação do Paciente , Educação de Pacientes como Assunto , Adulto , Cafeína/efeitos adversos , Ensaios Clínicos como Assunto , Ergotamina , Ergotaminas/efeitos adversos , Feminino , Humanos , Pessoa de Meia-Idade , Transtornos de Enxaqueca/psicologia , Distribuição Aleatória , Autoadministração
14.
Br J Pharmacol ; 88(4): 847-56, 1986 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-2874861

RESUMO

We studied the synaptic pharmacology of an excitatory pathway in the neostriatum using electrophysiological techniques in tissue slices from rats. In response to single electrical stimuli, two negative, extracellular potentials (N-1 and N-2) were recorded through micropipette electrodes within 150-450 micron of the stimulating cathode. N-2 was reversibly reduced or abolished by reducing the concentration of calcium in the bathing medium, while N-1 was unaffected. Both N-1 and N-2 were reversibly abolished by the local anaesthetic procaine. Single-unit, extracellular action potentials were, at times, associated with either N-1 or N-2. Intracellular recordings showed action potentials at N-2 latency arising from graded, monophasic, depolarizing potentials. Bath-applied cholinoceptor and dopamine receptor antagonists failed to reduce N-2. By contrast, antagonists of excitatory amino acid transmitters reversibly reduced or abolished N-2. gamma-D-Glutamylglycine (GG), (+/-)-cis-2,3-piperidine dicarboxylic acid (PDA) and DL-2-amino-4-phosphonobutyric acid (APB) blocked N-2 with ED50S of 0.79 mM, 1.0 mM and 1.1 mM, respectively. (-)-Baclofen reversibly blocked N-2 with an ED50 of 0.79 microM; (+)-baclofen was 330 times less potent. The results suggest that N-1 results from direct activation of fibre tracts or cell bodies, while N-2 is a population spike mediated by excitatory synapses whose natural transmitter pharmacologically resembles glutamate.


Assuntos
Corpo Estriado/efeitos dos fármacos , Glutamatos/farmacologia , Neurotransmissores/farmacologia , Sinapses/efeitos dos fármacos , Animais , Anticonvulsivantes/farmacologia , Baclofeno/farmacologia , Bicuculina/análogos & derivados , Bicuculina/farmacologia , Relação Dose-Resposta a Droga , Estimulação Elétrica , Eletrofisiologia , Potenciais Evocados/efeitos dos fármacos , Ácido Glutâmico , Relaxantes Musculares Centrais/farmacologia , Neurotransmissores/antagonistas & inibidores , Ácidos Pipecólicos/farmacologia , Procaína/farmacologia , Ratos , Ratos Endogâmicos
15.
Pharmatherapeutica ; 4(2): 132-40, 1985.
Artigo em Inglês | MEDLINE | ID: mdl-4059292

RESUMO

Sixty patients suffering from Parkinson's disease, irrespective of previous treatment, were recruited and treated with benserazide/l-dopa or carbidopa/l-dopa, randomly allocated, in a double-blind comparative study. Duration of disease on entry was 1 year or less in 70% of patients and was graded as moderate in 55% of patients. Mean age of patients on entry was 76 years for males and 80 years for females. Assessments were made before treatment and after 1 week, 3 weeks, 6 weeks and, finally, at 12 weeks. The dosage of drug was titrated at each visit to give minimum risk with acceptable benefit. Both drugs effectively improved the disability scores of the parkinsonian symptoms and the Sheffield Unit's Activities of Daily Living scores, the latter showing the immediate benefit for the patient in terms of independence. More patients improved in the benserazide/l-dopa-treated group. Furthermore, apart from one activity the improvement in each individual symptom and activity was greater in the benserazide/l-dopa-treated group, but none of the differences reached a statistically significant level. Adverse events recorded during the study were few and in many cases transient. Two patients defaulted (1 on each treatment) and 7 patients died during the study from non-drug-related causes.


Assuntos
Inibidores das Descarboxilases de Aminoácidos Aromáticos , Levodopa/uso terapêutico , Doença de Parkinson/tratamento farmacológico , Atividades Cotidianas , Idoso , Benserazida/administração & dosagem , Benserazida/efeitos adversos , Benserazida/uso terapêutico , Carbidopa/administração & dosagem , Carbidopa/efeitos adversos , Carbidopa/uso terapêutico , Quimioterapia Combinada , Feminino , Humanos , Levodopa/administração & dosagem , Levodopa/efeitos adversos , Masculino , Pessoa de Meia-Idade , Doença de Parkinson/fisiopatologia
16.
Curr Med Res Opin ; 9(7): 505-10, 1985.
Artigo em Inglês | MEDLINE | ID: mdl-2863089

RESUMO

A double-blind, multi-centre study was carried out in general practice to compare the efficacy and tolerance of treatment with bromazepam and lorazepam in 671 patients with anxiety. Patients were treated at random with either bromazepam (3 to 9 mg per day) or lorazepam (1 to 3 mg per day) for periods up to 2 weeks. In the doctors' global assessment of response, significantly more patients improved on bromazepam (84%) compared with lorazepam (77%). Thirty-three percent of the bromazepam patients reported at least one unwanted event compared with 37% in the lorazepam group. The results are discussed in the context of improving the benefit-risk ratio.


Assuntos
Ansiolíticos/uso terapêutico , Transtornos de Ansiedade/tratamento farmacológico , Bromazepam/uso terapêutico , Lorazepam/uso terapêutico , Adulto , Idoso , Transtornos de Ansiedade/psicologia , Bromazepam/efeitos adversos , Ensaios Clínicos como Assunto , Método Duplo-Cego , Feminino , Humanos , Lorazepam/efeitos adversos , Masculino , Pessoa de Meia-Idade , Distribuição Aleatória , Risco
17.
Curr Med Res Opin ; 8(10): 714-9, 1984.
Artigo em Inglês | MEDLINE | ID: mdl-6144456

RESUMO

A double-blind study was carried out in 312 patients seen by their general practitioner for a sleep disorder requiring hypnotic treatment to compare the efficacy and event profile of flunitrazepam and triazolam. Patients were allocated at random to receive a night-time dose of 1 mg flunitrazepam or 0.25 mg triazolam for a minimum of 7 and a maximum of 14 nights. Sleep disturbances, classified as difficulty in falling asleep, troublesome awakenings in the first or the second half of the night, and early morning awakening, were assessed on the initial and final visits and details of any events recorded. The results showed no significant difference between the two treatments with respect to efficacy and event profile and the findings are discussed in the context of the differing pharmacokinetics of the two drugs.


Assuntos
Ansiolíticos/uso terapêutico , Flunitrazepam/uso terapêutico , Transtornos do Sono-Vigília/tratamento farmacológico , Triazolam/uso terapêutico , Adolescente , Adulto , Idoso , Método Duplo-Cego , Medicina de Família e Comunidade , Feminino , Flunitrazepam/efeitos adversos , Humanos , Masculino , Pessoa de Meia-Idade , Triazolam/efeitos adversos
19.
Neurology ; 31(9): 1148-51, 1981 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-7196538

RESUMO

Cerebral sarcoidosis was found at autography in a 68-year-old woman with progressive dementia. Of 35 previously reported cases of central nervous system sarcoidosis with dementia, only 1 was over 65 years old, and in only 2 was the presenting clinical syndrome that of a degenerative dementia. Other unusual features of the index case include the restriction of the initial cognitive deficit to memory loss and mild anomia, the scarcity of antemortem evidence for systemic sarcoidosis, a positive tuberculin test, a cerebrospinal fluid (CSF) protein concentration as high as 2028 mg per deciliter. sarcoidosis is a rare but potentially treatable cause of dementia. Consistently normal CSF probably excludes the diagnosis.


Assuntos
Encefalopatias/diagnóstico , Demência/diagnóstico , Sarcoidose/diagnóstico , Idoso , Encefalopatias/complicações , Diagnóstico Diferencial , Feminino , Humanos , Transtornos Neurocognitivos/diagnóstico , Transtornos Neurocognitivos/etiologia , Sarcoidose/complicações
20.
Brain Res ; 151(2): 291-306, 1978 Aug 04.
Artigo em Inglês | MEDLINE | ID: mdl-209864

RESUMO

The relative importance of active and passive transport processes in the clearing of potassium released from active neurons was estimated Extracellular potassium activity [K+]0 was measured with ion-selective microelectrodes in the sensory area of the neocortex and in lumbosacral spinal cord of cats. Transient elevation of [K+]0 was evoked in cortex by stimulation of VPL and in spinal cord by stimulation of afferent nerves. The rate with which excess [K+]0 was cleared was either feebly or not at all influenced by variation of the intensity and frequency of stimulation. The half-decay times of [K+]0 were however prolonged when the duration of stimulus trains was increased. Only small differences were seen in the rate of decay of [K+]0 transients recorded at different locations within the gray matter; the shortest half-decay times occurred where K+ responses were largest. The different profiles of distribution of delta [K+]0 in response to stimulation of the cortical surface and of VPL nucleus were mapped. As in spinal cord also in cortex the distribution of the evoked sustained shifts of electric potential mirrored the distribution of [K+]0 transients. The rate at which K+ could diffuse out of volume sources similar in magnitude to the volumes of distribution of [K+]0 responses in gray matter were calculated. The observed half-decay times of [K+]0 transients were more than a hundred times shorter than those calculated for diffusion either in spinal cord or in cortex. Intravenous administration of digitoxigenin was shown to retard the clearing of [K+]0 and caused an elevation of the unstimulated [K+]0 baseline. Seizures were frequently induced by digitoxigenin when the [K+]0 baseline was only slightly elevated, and the occurrence of seizures was not associated with a definable threshold level of [K+]0. It is concluded that active reuptake is the principal mechanism of the clearing of [K+]0 released by neurons. Redistribution of K+ by diffusion must have been negligible under the conditions of these experiments, but may be more important when only a few neurons release K+ amongst many inactive cells. Considerations of a glial transport network are probably inconsequential for theories of the generation of seizures.


Assuntos
Córtex Cerebral/metabolismo , Espaço Extracelular/metabolismo , Potássio/metabolismo , Medula Espinal/metabolismo , Vias Aferentes/fisiologia , Animais , Transporte Biológico Ativo/efeitos dos fármacos , Gatos , Córtex Cerebral/fisiologia , Difusão , Digitoxigenina/farmacologia , Estimulação Elétrica , Potenciais Evocados/efeitos dos fármacos , Feminino , Masculino , Neurônios/metabolismo , Medula Espinal/fisiologia , Transmissão Sináptica/efeitos dos fármacos , Núcleos Talâmicos/fisiologia
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