RESUMO
PURPOSE: To investigate sensory nerve conduction of the caudal nerve in normal and diabetic rats. METHODS: Diabetes was induced in twenty 8-weeks old Wistar male rats. Twenty normal rats served as controls. Caudal nerve conduction studies were made before diabetes induction and the end of each week for six consecutive weeks. The caudal nerve was stimulated distally and nerve potentials were recorded proximally on the animal's tail using common "alligator" clips as surface electrodes. RESULTS: After induction, nerve conduction velocities (NCV) increased slower in the diabetic than in the control group. Sensory nerve action potentials (SNAP) conduction velocities increased slower in the diabetic than in the control group (slope of regression line: 0.5 vs 1.3m/s per week; NCV in the 15(th) week = 39±3m/s vs 44±4m/s). Tukey's tests showed differences between groups at the 11th, 13(th) and 15(th) weeks old. From the 10(th) week on, SNAP amplitudes increased faster in the diabetic than in the control group (slopes of the regression line: 10 vs 8µV per week; SNAP amplitudes in the 15(th) week: 107±23µV vs 85±13µV). Differences at the 12(th), 13(th) and 15(th) weeks were significant. CONCLUSION: In diabetic rats nerve conduction velocities were slower whereas amplitudes were larger than in normal rats.
Assuntos
Diabetes Mellitus Experimental/fisiopatologia , Condução Nervosa/fisiologia , Cauda/inervação , Animais , Masculino , Ratos , Ratos WistarRESUMO
Purpose: To non-invasively study the sensory nerve conduction of the caudal nerve of normal developing rats. Methods: Twenty normal Wistar male rats served as subjects. Caudal nerve conduction studies were performed at 60 days from birth and weekly at end of six consecutive weeks. The caudal nerve was stimulated distally and nerve potentials were recorded proximally on the animal's tail using common "alligator" clips as surface electrodes. Results: The amplitude and the conduction velocity of the caudal nerve sensory action potential increased linearly from 29±6 µV to 85±13 µV and from 34±3 m/s to 44±4 m/s, respectively, between the 8th and the 15th week of life. The equations of linear regressions were as followed: Amplitude (µV) = 8.1 × weeks - 34 (R² = 0.99) and NCV (m/s) = 1.2 × weeks + 25 (R² = 0.86). Conclusions: It was possible to study non-invasively the sensitive conduction of the caudal nerve of normal developing rats and describe reference values. The technique and data may be used as animal model in physiological and pathological studies.
Objetivo: Estudar de forma não invasiva a condução nervosa sensitiva do nervo caudal em ratos normais em desenvolvimento. Métodos: Vinte ratos machos Wistar foram utilizados. A conducão nervosa foi realizada a partir dos 60 dias, semanal durante seis semanas consecutivas. O nervo caudal foi estimulado distalmente, os potenciais foram registrados proximalmente na cauda do animal usando garras comum do tipo "jacaré" como eletrodos de superficie. Resultados: A amplitude do potencial de ação de nervo sensitivo a velocidade de condução nervosa do nervo caudal cresceu linearmente de 29 ± 6 µV para 85 ± 13 µV e de 34 ± 3 m/s para 44 ± 4 m/s, respectivamente, entre a 8º e a 15º semana da vida do animal. As equações de regressão linear foram as seguintes: Amplitude (µV) = 8,1 × semanas - 34 (R² = 0,99) e velocidade de conducao nervosa (m/s) = 1,2 × semanas + 25 (R² = 0,86). Conclusões: Foi possível estudar de forma não invasiva a condução nervosa sensitiva do nervo caudal de ratos normais em desenvolvimento e descrever valores de referência. A técnica e os dados podem ser usados como modelo animal em estudos fisiológicos e patológicos.
Assuntos
Animais , Masculino , Ratos , Estimulação Elétrica/métodos , Condução Nervosa/fisiologia , Nervos Periféricos/fisiologia , Cauda/inervação , Ratos Wistar , Tempo de ReaçãoRESUMO
PURPOSE: To non-invasively study the sensory nerve conduction of the caudal nerve of normal developing rats. METHODS: Twenty normal Wistar male rats served as subjects. Caudal nerve conduction studies were performed at 60 days from birth and weekly at end of six consecutive weeks. The caudal nerve was stimulated distally and nerve potentials were recorded proximally on the animal's tail using common 'alligator' clips as surface electrodes. RESULTS: The amplitude and the conduction velocity of the caudal nerve sensory action potential increased linearly from 29+/-6 microV to 85+/-13 microV and from 34+/-3 m/s to 44+/-4 m/s, respectively, between the 8th and the 15th week of life. The equations of linear regressions were as followed: Amplitude (microV) = 8.1 x weeks - 34 (R(2) = 0.99) and NCV (m/s) = 1.2 x weeks + 25 (R(2) = 0.86). CONCLUSIONS: It was possible to study non-invasively the sensitive conduction of the caudal nerve of normal developing rats and describe reference values. The technique and data may be used as animal model in physiological and pathological studies.
Assuntos
Estimulação Elétrica/métodos , Condução Nervosa/fisiologia , Nervos Periféricos/fisiologia , Cauda/inervação , Animais , Masculino , Ratos , Ratos Wistar , Tempo de ReaçãoRESUMO
Adult male albino rats were exposed to varying numbers of tailshocks (0, 10, 50 or 100). The following day, their escape latencies in a shuttlebox were measured in order to estimate the degree of learned helplessness (LH) produced by the varying number of shocks. Only the groups exposed to 50 or 100 shocks displayed evidence of LH. In a parallel experiment, c-fos activation was used to determine the degree of activation of raphe serotonergic neurons (FosIR+5-HT) and locus coeruleus (LC) noradrenergic neurons (FosIR+TH) produced by the same shock conditions. Compared to unhandled cage controls, all shock groups (0 shocks was a restrained group) significantly activated both raphe and LC neurons. The 50 and 100 shock groups had significantly higher degrees of activation of serotonergic neurons in the rostral raphe groups and the LC than the 0 and 10 shock groups. These data are consistent with the hypothesis that activation of rostral raphe serotonergic neurons and LC noradrenergic neurons beyond a certain threshold may be critical for the development of LH. The relevance of these results for elucidating the neural bases of psychopathology is discussed.
Assuntos
Eletrochoque/efeitos adversos , Desamparo Aprendido , Neurônios/fisiologia , Norepinefrina/metabolismo , Serotonina/metabolismo , Análise de Variância , Animais , Comportamento Animal , Contagem de Células/métodos , Reação de Fuga/fisiologia , Reação de Fuga/efeitos da radiação , Imuno-Histoquímica/métodos , Locus Cerúleo/citologia , Locus Cerúleo/metabolismo , Masculino , Proteínas Oncogênicas v-fos/metabolismo , Distribuição Aleatória , Ratos , Ratos Sprague-Dawley , Esquema de Reforço , Cauda/inervação , Cauda/efeitos da radiação , Tirosina 3-Mono-Oxigenase/metabolismoRESUMO
Thyroid hormones (THs), primarily 3,3',5-triiode-(L)-thyronine (T(3)), have been clearly established as natural inducers of apoptosis during metamorphosis of anuran embryos. We decided to use this phenomenon to test the hypothesis that, prior to genomic activation, T(3) has acute actions in the neuromuscular junction (NMJ) of the tail of amphibian embryos. We detected a dramatic increase in the production of miniature end-plate currents (MEPCs) 2-5 min after continuous application of T(3) (250 nM) using focal recordings under voltage clamp. Furthermore, this increase in the spontaneous release of neurotransmitter, evaluated by the MEPC frequency, was maintained for several hours. Reverse-T(3), the "inhibitory" form of THs, prevented this increase in MEPC frequency, suggesting that this is probably a highly specific action of T(3). In addition, the elevation in MEPC frequency induced by T(3) was unchanged in the presence or absence of extracellular calcium. The T(3)-mediated increase in MEPC frequency was blocked by niflumic acid, a nonsteroidal antinflammatory fenamate used to prevent the apoptotic volume decrease observed in many systems. The present study demonstrated that T(3) induces a remarkable nongenomic action in the NMJ of the tadpole tail at pre- and promatamorphic stages.
Assuntos
Metamorfose Biológica/fisiologia , Junção Neuromuscular/efeitos dos fármacos , Cauda/inervação , Tri-Iodotironina Reversa/farmacologia , Tri-Iodotironina/farmacologia , Acetilcolina/metabolismo , Animais , Cálcio/metabolismo , Canais de Cloreto/antagonistas & inibidores , Espaço Extracelular/metabolismo , Técnicas In Vitro , Larva , Potenciais da Membrana/efeitos dos fármacos , Potenciais da Membrana/fisiologia , Junção Neuromuscular/metabolismo , Junção Neuromuscular/fisiologia , Neurotransmissores/metabolismo , Ácido Niflúmico/farmacologia , Técnicas de Patch-Clamp , Rana catesbeiana , Cauda/efeitos dos fármacos , Cauda/fisiologia , Tri-Iodotironina/antagonistas & inibidoresRESUMO
We studied the effects of prolonged high-frequency stimulation in normal rat tail nerves. Nerves could conduct impulses at 50 Hz for 5 hours without complete conduction block. However, over time there was a significant decrease in amplitude and increase in latency of the compound nerve action potential (CNAP), which gradually became desynchronized. Changes were influenced by the frequency of stimulation. When stimulating over 30 minutes at 20, 50, 100, and 143 Hz the amplitude decreased to 89%, 79%, 67%, and 65% of baseline values, respectively, whereas the latency was only significantly increased at 100 and 143 Hz. All changes were reversible upon cessation of stimulation. Changes could not be attributed to focal block at the site of stimulation. These changes in the CNAP may reflect functional limitations of the axon membrane which may have pathophysiological implications for the study of neuropathies and focal nerve lesions.