Neuroscience letters
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Neuroscience letters · Oct 1985
Comparative StudyTarget dependence of Nissl body ultrastructure in cat thoracic motoneurones.
The effects on Nissl body (NB) ultrastructure of muscle reinnervation or neuroma formation were determined in cytochemically identified cat thoracic motoneurones subjected to axotomy by either nerve crush or nerve section with proximal ligation. Normal NB ultrastructure comprised highly ordered lamellae of rough endoplasmic reticulum (RER) with associated linear arrays of unbound polyribosomes. ⋯ While NBs were seen in the light microscope at late stages following both nerve crush or ligation, normal NB ultrastructure was only observed following nerve crush. An inductive effect of the periphery on NB ultrastructure is proposed and the implication of NB ultrastructure discussed in relation to protein synthesis.
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Neuroscience letters · Jun 1984
Comparative StudyPhasic paradoxical sleep precipitates focal motor and limbic seizures.
The facilitatory or inhibitory effect of paradoxical sleep (PxS) was investigated in two models of focal epilepsy: focal motor seizures induced by alumina cream in the frontal cortex and limbic seizures produced by intra-amygdaloid kainic acid microinjections in cats. We found that phasic episodes of PxS could trigger both types of seizures. ⋯ We conclude that PxS exerts facilitatory or inhibitory effects depending on the particular event under analysis and the degree of epileptogenicity. The capacity of phasic PxS to precipitate focal ictal discharges may depend on ponto-limbic excitatory influences.
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Neuroscience letters · Jan 1984
Electrophysiological effects of GABA on fish retinal horizontal cells are blocked by bicuculline but not by picrotoxin.
We have studied electrophysiologically the actions of gamma-aminobutyric acid (GABA) and related pharmacological agents on fish retinal horizontal cells by recording intracellularly from isolated retinae perfused with Ringer containing the various drugs. We show that although GABA usually hyperpolarizes the membrane potential relative to its dark level, it sometimes and particularly at higher (greater than or equal to 5 mM) concentration produces membrane depolarization, with reduction in the light evoked responses (S-potentials) in both cases. ⋯ The GABA uptake blocker nipecotic acid [15] hyperpolarizes horizontal cells and reduces their light evoked responses, and again these effects are reversed by bicuculline but not by picrotoxin. beta-Alanine, which blocks glial GABA transport [29], and diaminobutyric acid (DABA), which blocks neuronal GABA transport [14, 29, 31], have effects similar to those of nipecotic acid. We discuss these actions of GABA and of the other related drugs and their differential sensitivity to bicuculline and picrotoxin.
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CO2 laser emitted radiant heat pulses of 20 ms duration were used to activate predominantly slowly conducting nociceptive cutaneous afferents in man. Stimuli of two-fold individual pain threshold caused stinging and burning pain and elicited cerebral potentials with latencies consistent with A delta-fibre activity. After preferential block of the myelinated nerve fibres by pressure only the burning pain remained with significantly increased reaction time (about 1433 ms). The A delta-fibre-induced evoked potential components disappeared, and a marked ultralate positive component became visible with mean peak latency of 1260 ms, consistent with C-fibre activity.
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While brain weight scales to body weight, the differences among brain weights are less than those among body weights. It has been assumed that this negative scaling is causally related to an isometric scaling of brain weight with surface area. ⋯ Morphometric data indicate that this is not the case. Interspecific scaling of mammalian brain sizes, however, is isometric with the organisms' abilities to support the energy costs of the brain.