Neirofiziologiia = Neurophysiology最新文献

Distribution of primuline, fast blue, fluoro-gold and nuclear yellow-labelled monoamine-containing cells in periventricular gray and dorsolateral tegmentum (including locus coeruleus) was studied in the rat after injection of these fluorochromes into the frontal cortex, hypothalamus and spinal cord. Combination of monoamine fluorescence method and retrograde cell-labelling was used. Two big groups of serotonin-positive cells projecting into the upper thoracic spinal segments were found in dorsomedial zone of the dorsal raphe. Part of these units also had divergent axon projections to the frontal cortex. Such cellular arrangement allows a supposition that analgetic effects of dorsal raphe stimulation can be partially based on the direct participation of this structure in the descending control at the spinal level. Neurones, sources of cortical projections are intermingled with the cells projecting to the hypothalamus but some topical differentiation can be distinguished. Neurotransmitter and neuroregulatory roles of separate cortical and hypothalamic projections of serotonin-containing neurons of the dorsal raphe cells is discussed.

Amplitude of the L5 segmental reflex responses 20 min. before and after intraperitoneal introduction of obsidan, clopheline and finoptine was recorded in experiments on spinalized and thyroxinized rats which 3 weeks before have endured transection of the sciatic nerve. It is demonstrated that obsidan does not change the amplitude of the monosynaptic reflex responses of the ventral root restored under the effect of thyroxine at the operated side, while clopheline and finoptine mainly reduce it.

The new technique has been used to realize paired short-term application of glutamate to whole dialyzed neuron. Desensitization of receptors via first application of glutamate resulted in incomplete recovery of the current evoked by the second application if interval between both applications was less than 160 ms. The recovery time constant of the current was found to be 44 ms at single exponential approximation. It is close to the mean desensitization time constant of the current evoked by single prolonged application of glutamate. Rhythmic application of glutamate resulted in a rapid fall of the mean current amplitude at frequencies over 10 Hz. Data obtained by the authors confirm the known concept of desensitization of non-NMDA receptors as a relatively slow conformation of the receptor-channel complex.

Neuronal impulse activity in the sensorimotor cortex after Substantia Innominata (SI) stimulation has been studied in cats during conditioned placing with food reinforcement. SI stimulation was delivered 1 or 3 seconds before the conditioned sound stimuli. The results of the investigation show that SI stimulation does not change sensorimotor cortex impulse activity but at the same time it inhibits the background activity. Reactions of 32% (after 1 s) and 33% (after 3 s) of the somatosensory cortex neurones were increased to conditioned stimuli and conditioned movement after preliminary SI stimulation. The appearance of impulse responses in some neurones which showed no initial reactions to conditioned stimuli was caused by SI stimulation. Preliminary SI stimulation may cause not only excitatory but also inhibitory effect on somatosensory cortical neurones. In case of 1 s interval between SI stimulation and conditioned stimuli presentation there were only 6% of cells with such inhibition, but in case of 3 s interval there were 33% of such reactions. SI stimulation shortened the latencies of the conditioned movement 2-3 times. Modulatory influence of acetylcholine from SI neurones to neocortical activity is discussed.

Mechanisms of the exogenic acetylcholine (ACh) effect on ionic currents of nerve endings (NE) were investigated by extracellular recording of NE at the cutaneous pectoris muscle of frog. It was found that ACh in concentrations 0.1-0.6 mmol/l increased the third phase of the nerve ending response, while in concentrations 0.7-2.0 mmol/l-decreased it. Tubocurarine and atropine did not alter the ACh effect. It has been also revealed that growth of the third phase of NE response, induced by ACh, occurs in the presence of calcium channel blockers and disappears under the influence of 4-aminopyridine and tetraethylammonium. In calcium-free solution or when the calcium current is blocked the suppressive effect of ACh disappears. The mechanisms of exogenic and endogenic ACh effects on the potential-sensitive and calcium-activated potassium NE currents are discussed.

Serotonin (5-HT) added to washing solution has been studied for its effect on plastic properties of electrically excitable membranes of the parietal ganglion and identified PPa2 neurons in the isolated nerve system of snails. It is shown that neurons habituated to intracellular stimulation are able to restore action potential generation in the presence of 5-HT. Contrary, neurons possessing endogenous rhythmic activity (PPa2) generate train activity on the background of appearance of the membrane potential slow waves under the influence of 5-HT. A comparative analysis of 5-HT and chemicals with the known effect on activity of Ca and Ca-dependent K-channels (quinine, CoCl2, CdCl2) has demonstrated diversity of mechanisms underlying the 5-HT-ergic regulation of plasticity of the neuronal electrically excitable membrane. This difference stems from the processes of activation and blockade of Ca-dependent channels.

Studies of spontaneous firing (SF) in the midbrain periaqueductal gray (PAG) neurons before and after stimulation of nucleus raphe magnus, locus coeruleus and substantia nigra were performed on the rat anesthetized with Hexenal (200 mg/kg). Three types of neurons different in SF structure were found. Stimulation of indicated structures increased SF rate in 11-14.5% and decreased 31-47% of the studied neurons of the third group. Simultaneous stimulation of two structures did not induce a remarkable increase of SF rate. If one of two simultaneously stimulated structures suppressed SF the ultimate effect was, as a rule, depression of SF. Greatest suppression of SF was observed if stimulation of nucleus raphe magnus was induced. Role of PAG in organization of the brain stem component of antinociceptive mechanism is discussed.