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Results for “Ganglionic Stimulants”

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At least 505 records · Page 28Linked to original sources
PubMed1988

Effect of stimulation of the sphenopalatine ganglion on cortical blood flow in the rat.

The effects of electrical stimulation of the sphenopalatine ganglion on cortical blood flow and gas partial pressures (PO2 and PCO2) were studied in the anesthetized rat. Tissue PO2, PCO2, and local CBF were measured simultaneously in both parietal cortices by means of mass spectrometry. Stimulation of the sphenopalatine ganglion increased CBF and tissue PO2 by approximately 50 and 20%, respectively, in the ipsilateral parietal cortex. Smaller but significant increases in CBF and tissue PO2 were simultaneously seen in the contralateral parietal cortex. These variations were also accompanied by small decreases in PCO2 in both parietal cortices and a 5% increase in mean arterial pressure, whereas cortical electrical activity did not change. We conclude that the cholinergic (and vasoactive intestinal polypeptidergic) innervation of the cerebral blood vessels, arising from the sphenopalatine ganglion has significant vasomotor potential and that this system may be of functional importance.

Acetylcholine↗
PubMed1992

Cerebral blood flow changes induced by electrical stimulation of the Gasserian ganglion after experimentally induced subarachnoid haemorrhage in pigs.

The effect of trigeminal electrical stimulation on cerebral blood flow has been studied in conditions of normal or reduced cerebral blood flow (CBF). Autologous blood was injected into the subarachnoid space of ten Pittmann-Moore pigs to induce subarachnoid haemorrhage (SAH) accompanied by cerebral blood flow (CBF) reduction. One week later, in six of ten animals, a considerable decrease of CBF was noted as evaluated by means of a recording-system monitoring over the right parieto-temporal calvarium the washout of 133Xenon injected into the internal carotid artery after the external carotid had been clamped. Continuous electrical stimulation of the Gasserian ganglion performed in the six animals with severely induced CBF reduction produced a remarkable cerebrovascular dilation and increase of CBF lasting over 3 h. Electrical stimulation of the Gasserian ganglion produced a similar pattern of vasodilation in six pigs in which no blood was injected and no reduction of CBF was evident. The mechanisms and the anatomical pathways which underlie these results are discussed.

Animals↗
PubMed1979

Vitellogenesis stimulated by thoracic ganglion implants into destalked immature spider crabs, Libinia emarginata.

Since destalked immature female Libinia emarginata fail to molt to maturity (Hinsch, 1972) and implants of thoracic ganglion of adult females into young females of Potamon dehaani caused a doubling of ovarian weight and differentiation of yolk granules (Otsu, 1963), the effects of the thoracic ganglion implantation on sexual maturation in Libinia was investigated. Destalked immature Libinia with a maximum carapace length of 4-5 cm received two implants of adult female thoracic ganglion at 10-day intervals. All of the surviving experimental animals and destalked controls molted to immaturity. Most of the experimental animals failed to complete a successful molt and few survived longer than 3-4 days. The experimental animals that survived for over a week showed signs of yolk deposition not observed in the destalked controls. Eggs in several stages of vitellogenesis were scattered throughout the gonad in the animal showing the most pronounced effect. This was not observed in any of the destalked controls.

Animals↗
PubMed2001

Effects of remote stimulation on the mean firing rate of cat retinal ganglion cells.

Visual stimulation outside the classical receptive field can have pronounced effects on cat retinal ganglion cells. We characterized the effects of such stimulation by varying the contrast, spatial frequency, temporal frequency, and spatial extent of remote drifting sinusoidal gratings. We found that the mean firing rate of some X-cells and most Y-cells increased to remote gratings of low spatial frequency and high temporal frequency and decreased to ones of high spatial frequency and low temporal frequency. At least 10-20% contrast was required to see either effect, which quickly saturated at higher contrasts. Both effects were substantial, raising or lowering the mean rate of some cells by over 40 impulses/sec. Classical receptive field mechanisms were not involved because the remote gratings caused little or no response modulation. We conclude that, in addition to a mean-increasing mechanism known from previous work, a mean-decreasing one operates in the cat retina. This mechanism prefers slower motion and resolves finer patterns than the mean-increasing one. We incorporate these findings into a model consisting of pools of small and large rectifying subunits of opposite polarity. Model estimates of subunit radius were primarily independent of eccentricity and averaged approximately 0.15 and approximately 0.60 degrees for the mean-decreasing and mean-increasing mechanisms, respectively. This makes the subunits approximately the center size of central X- and Y-cells. Because smooth movements of the eyes, head, or body should engage these mechanisms under natural conditions, we propose that the mean rate changes that would ensue are functionally relevant to cat vision.

Action Potentials↗
PubMed2006

Tissue resistivities determine the current flow in the cochlea.

PURPOSE OF REVIEW: In individuals with severe to profound hearing loss, cochlear implants bypass normal inner ear function by applying electrical current directly into the cochlea, thereby stimulating cochlear nerve fibers. Stimulating discrete populations of spiral ganglion cells in cochlear implant users' ears is similar to the encoding of small acoustic frequency bands in a normal-hearing person's ear. Thus, spiral ganglion cells stimulated by an electrode convey the information contained by a small acoustic frequency band. Problems that refer to the current spread and subsequent nonselective stimulation of spiral ganglion cells in the cochlea are reviewed. RECENT FINDINGS: Cochlear anatomy and tissue properties determine the current path in the cochlea. Current spreads largely via scala tympani and across turns. While most of the current leaves the cochlea via the modiolus, the facial canal and the round window constitute additional natural escape paths for the current from the cochlea. Moreover, degenerative processes change tissue resistivities and thus may affect current spread in the cochlea. SUMMARY: Electrode design and coding strategies may result in more spatial stimulation of spiral ganglion cells, resulting in a better performance of the electrode-tissue interface.

Cochlea↗
PubMed1997

Responses of the dural circulation to electrical stimulation of the trigeminal ganglion in the cat.

1. In cats anaesthetized with alpha-chloralose, electrical stimulation (ES) of the trigeminal ganglion produced a fall in blood pressure, a predominantly ipsilateral dilatation in the common carotid vascular bed and bilateral dilatation of the middle meningeal vascular bed. Section of the trigeminal root abolished these responses. 2. Dilatation in the middle meningeal artery was not affected by section of the cervical sympathetic trunk nor by the section of the seventh cranial nerve trunk. The dilator response was abolished by section of the spinal cord at the C3 level and by intravenous administration of bretylium (10 mg/kg) or phentolamine (5 mg/kg). The response was significantly reduced by the prior administration of papaverine (10 mg/kg). 3. Functional adrenalectomy by means of a snare placed around the nerves and blood vessels supplying the adrenal glands significantly reduced the response. Electrical stimulation of the trigeminal ganglion was accompanied by a fall in circulating levels of noradrenaline and serotonin. 4. We conclude that ES of the trigeminal ganglion produces dilatation in the middle meningeal artery partly by autoregulation during the trigeminal depressor response and partly by a reduction in the circulating levels of noradrenaline. It differs from the dilatation seen in the general carotid circulation and the cortical microcirculation, which is mediated by parasympathetic nerves. There is no evidence that antidromic release of neuropeptides from sensory nerve endings in the dura plays a part in the dilatation.

Adrenalectomy↗
PubMed1985

Long-term regulation of tyrosine hydroxylase activity in the superior cervical ganglion in organ culture: effects of nerve stimulation and dexamethasone.

The rat superior cervical ganglion was stimulated in vitro via its preganglionic trunk and then maintained in organ culture for 2-3 days. Following nerve stimulation, the specific activity of tyrosine hydroxylase (TH) increased with a lag period of at least 12 h, and this increased enzyme activity was maintained throughout the culture period. The magnitude of the increase in TH activity depended on the frequency and duration of preganglionic nerve stimulation. This transsynaptic increase in enzyme activity could be completely blocked by the nicotinic antagonist, hexamethonium. The synthetic glucocorticoid dexamethasone, at concentrations above 1 nM, increased TH activity in unstimulated ganglia with a lag period of at least 24 h. The increase in enzyme activity produced by dexamethasone was not affected by nicotinic antagonists or by prior decentralization of the superior cervical ganglion, in contrast to the findings of previous workers. These data indicate that dexamethasone can stimulate ganglionic TH activity in the absence of cholinergic stimulation. In addition, experiments combining dexamethasone with nerve stimulation demonstrate that the steroid can potentiate the effects on TH activity of brief periods of nerve stimulation.

Animals↗