Electrophysiology stimulation

Pallidotomy has been an efficient surgical tool for treating patients who no longer responded adequately to L-DOPA therapy, and it is still indicated and performed in certain complex cases. Its efficacy is due to the fact that no electrophysiological stimulation in the pallidum is less deleterious than the overstimulation caused by the loss of dopaminergic projections from the substantia nigra. 

Fentanyl enhances vagal tone and can cause bradycardia. In 27 children undergoing catheter ablation under propofol anesthesia, which has minimal effect on the sinus node, electrophysiological stimulation was performed before and after a bolus dose of fentanyl 2 micrograms/kg and a subsequent infusion of 0.075 micrograms/kg/minute [64 ]. There was an increase in calculated sinus node recovery time but no change in sinoatrial conduction time after fentanyl, suggesting that fentanyl -I- propofol impairs sinus node recovery and therefore... 

At a cellular level, the activation of mAChRs leads to a wide spectrum of biochemical and electrophysiological responses [1, 5]. The precise pattern of responses that can be observed does not only depend on the nature of the activated G proteins (receptor subtypes) but also on which specific components of different signaling cascades (e.g. effector enzymes or ion channels) are actually expressed in the studied cell type or tissue. The observed effects can be caused by direct interactions of the activated G protein(s) with effector enzymes or ion channels or may be mediated by second messengers (Ca2+, DP3, etc.) generated upon mAChR stimulation. 

In a classical neural pathway, such as that depicted in Fig. 1.3, neuron A must excite neuron B and at the same time inhibit neuron C in order to optimise the excitation of B. It could achieve this with one NT able to activate receptors linked to different events on B and C. Of course, neuron C would have other inputs, some of which would be excitatory and if the same NT was used it could activate the inhibitory mechanism on C as well. Also, the NT released from A might be able to stimulate as well as inhibit neuron C (Fig. 1.3(a)). Even the provision of separate receptors linked to excitation and inhibition would not overcome these problems since both would be accessible to the NT. One possible solution, used in the CNS, is to restrict the NT to the synapse at which it is released by structural barriers or rapid degradation. Also the inputs and receptors linked to excitation could be separated anatomically from those linked to inhibition and, in fact, there is electrophysiological and morphological evidence that excitatory synapses are mainly on dendrites and inhibitory ones on the soma of large neurons (Fig. 1.3(b)). Nevertheless, the problem of overlap would be eased if two NTs were released, one to activate only those receptors linked to excitation and another to evoke just inhibition, i.e. place the determinant of function partly back on the NT (Fig. 1.3(c)). This raises a different problem which has received much consideration. Can a neuron release more than one NT ... 

Greenhoff, J and Johnson, SW (1997) Electrophysiological effects of dopamine receptor stimulation. In The Dopamine Receptors (Eds Neve, KA and Neve, RL), Humana Press, Totowa, NJ, pp. 267-304. 

The cellular actions of cannabinoids clearly support the proposal that the cannabinoid receptor is inhibitory and, consequently, reduces the firing rate of target neurons. However, this is not wholly confirmed by electrophysiological measurements, which suggest that cannabinoid compounds can stimulate neurons in the hippocampus. This apparent discrepancy may be due to the ability of cannabinoids to inhibit the release of an inhibitory substance in the hippocampus and, thus, produce a net excitation. 

In addition to autonomic effects, areca produces mental stimulation, increases cerebral blood flow and glucose metabolism, and creates electrophysiological activation as seen on the EEG. 

Heightened sensory perceptions Stimulates appetite Perceived slower passage of time Panic or anxiety Dissociative symptoms Physiological Effects Increases heart rate Reduces body temperature Slowed gastrointestinal function Electrophysiology... 

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