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At least 667 records · Page 37Linked to original sources
PubMed1988

Spontaneous release of acetylcholine affects the physiological nicotinic responses of rat retinal ganglion cells in culture.

Nictonic cholinergic responses have been previously documented in mammalian retinal ganglion cells. In the present study, dissociated retinal cells were densely plated and grown in a specific batch of rat serum. When held at negative potentials during whole-cell recording with a patch electrode, the retinal ganglion cells located close to presumptive cholinergic amacrine cells in these cultures were found to respond to acetylcholine (ACh; 20-200 microM) with an apparent outward current in the presence of physiological salines on both sides of the membrane. Other nicotinic agonists (nicotine, carbachol) produced the same effect. Conductance measurements revealed that this apparent outward current was actually a decrease in a tonic inward current. Nicotinic antagonists such as d-turbocurarine (10 microM) and dihydro-beta-erythroidine (20 microM), when applied in dishes that had never been exposed to exogenous ACh, produced a similar decrease in a tonic inward current. The reversal potential of the tonic current suppressed by ACh was similar to the nicotinic current previously studied in these central neurons. Furthermore, purified acetylcholinesterase was capable of modulating the tonic inward current of the retinal ganglion cells. Lowering an excised patch of muscle into dense areas of the retinal cultures activated nicotinic channels in the muscle membrane, indicating the presence of endogenous ACh in the culture fluid. Divalent cations such as Co2+ blocked the tonic inward current of retinal ganglion cells in these cultures. Finally, direct biochemical measurements indicated that low levels of endogenous ACh (on the order of 0.5 microM near putative cholinergic amacrine cells) were present in the retinal cultures. Taken together, these results show that ACh was being spontaneously released into these cultures, resembling at least to some degree the tonic leakage of ACh found in the intact retina. This concentration of ACh was capable of tonically depolarizing the membrane potential of retinal ganglion cells exposed to this dosage. This culture system allows the study of trophic effects of ACh on a central mammalian neuron in a precisely controlled extracellular environment.

Acetylcholine↗
PubMed1993

Chemical blockage of cervical sympathetic trunks for facial palsy.

Impairment of microcirculation of the facial nerves is considered to play an important role in etiology of facial palsy, and the main emphasis of the conservative treatment is aimed at circulatory improvement. Therefore, at the pain clinic, improved blood flow to the facial nerve by chemical blockage of cervical sympathetic trunks (stellate ganglion block; SGB) is employed in treating patients with facial palsy. The circulatory effects of SGB were clinically determined in 20 patients with acute Bell's palsy, and the effects of chemical blockage of cervical sympathetic trunks on the tissue circulation of facial nerve were also experimentally evaluated in dogs. In the clinical study, the blood flow volume of the common carotid artery increased significantly in 5 minutes after SGB, and has reached its peak of 176.4% in 20 minutes. This significant increase continued up to 75 minutes. In the animal model experiments, the common carotid arterial blood flow volume increased immediately after performing experimental SGB with a peak rise of 143.5% in 15 minutes, and the significant increase continued up to 45 minutes. The blood flow volume in the facial nerve tissue also increased for 5 minutes with a peak rise of 115.2% in 20 minutes after SGB, and this significant increase persisted for up to 60 minutes. A marked increase was observed in the blood flow volume in the facial nerve tissue as well as through the common carotid artery. The circulatory improvement performed by SGB extended as far as the facial nerve itself. From the facts above mentioned, SGB is considered to be an extremely effective treatment for the Bell's palsy.

Adolescent↗