PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Stimulation, Chemical”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources
PubMed1977

[Increase in stability of isolated tissues and proteins caused by the action of chemical stimulants].

Chemical agents in subtoxic concentrations prolongate the survival time of living muscles and the time of contractile ability of glycerinated muscles. They preserve also the native property of actomyosine over the control time. The increase of resistance of living muscles and their models may be explained by stabilization of proteins or of their complexes. It is accompanied by the change of the indices of the functional state of the living muscle--by the decrease of the binding of vital dyes, by the hyperpolarization, by reducing the consumption of O2 and by the conservation of the quantity of SH groups at the high level.

Actomyosin↗
PubMed1979

A modification of the dialytrode for simultaneous CNS recording and chemical stimulation.

Currently, chemical stimulation of the brain is done either with a single cannula that is inserted at the time the drug is delivered or with two cannulae that permit perfusion of the area of interest. The dialytrode is a push-pull cannula consisting of two concentric tubes, a porous membrane covering the tip of the tubing and a platinum wire loop that extends around the membrane and is used for EEG recordings. Studies with the dialytrode indicate that while the membrane is relatively impermeable to bacteria, molecules the size of neurotransmitters pass easily through the membrane. Therefore, the dailytrode is well suited for chronic chemical stimulation studies.

Amygdala↗
PubMed1978

Chemical stimulation of single human fungiform taste papillae: sensitivity profiles and locus of stimulation.

Psychophysical responses to chemical stimulation of single human fungiform taste papillae were obtained from 40 papillae in four subjects. Effects of solution concentration and locus of stimulation were examined for nine test compounds. Sensitivity profiles constructed for individual papillae showed that single fungiform papillae mediate more than a single taste quality. In addition, the chemical sensitivities of individual papillae were reflected in their thresholds for all compounds, and correlation coefficients between recognition thresholds were no greater for similar than for dissimilar tasting compounds. No differences in mediation of quality were found as a function of locus of stimulation on the papilla, although sensitivity was found to be greater on the dorsal surface than on the sides. The data were discussed within the context of previous studies of response characteristics of single papilla.

Adolescent↗
PubMed1991

Chemical stimulation of the ventrolateral medullary depressor area decreases ipsilateral cerebral blood flow in anesthetized rats.

In anesthetized (chloralose and urethane), paralyzed and artificially ventilated rats, the neurons in the ventrolateral medullary depressor area (VLDA) were chemically stimulated by microinjections of L-glutamate (2.5-5 nmole in 100 nl of 0.9% sodium chloride solution) and the cerebral blood flow (CBF) was determined using a combination of labeled microspheres (57Co, 113Sn and 46Sc). Unilateral chemical stimulation of the VLDA (n = 11) produced a significant (P less than 0.05) decrease in CBF of the cerebral cortex ipsilateral to the stimulated VLDA; the CBF was 41 +/- 5 (mean +/- S.E.M.) and 29 +/- 4 ml.min-1.(100 g)-1 before and during the chemical stimulation of VLDA. The decrease in CBF was not due to the decrease in arterial blood pressure (ABP) caused by the chemical stimulation of the VLDA because the CBF during the chemical stimulation of the VLDA was significantly smaller (P less than 0.01) than the CBF during controlled hemorrhagic hypotension (n = 10). In another group of rats (n = 6), moderate hypertension was induced by blood transfusion. Unilateral chemical stimulation of the VLDA in these rats decreased ABP but it remained within normotensive range. A significant (P less than 0.05) decrease in CBF (from 46 +/- 12 to 29 +/- 7 ml.min-1.(100 g)-1) and a significant (P less than 0.01) increase in cerebrovascular resistance (from 2.7 +/- 0.4 to 4.3 +/- 0.6 mmHg per [ml.min-1.(100 g)-1]) was observed in the ipsilateral cerebral cortex of these rats. Chemical stimulation of the VLDA did not affect the reactivity of the cerebral vessels to hypercapnea (n = 5).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Chemical stimulation of the nucleus tractus solitarii decreases cerebral blood flow in anesthetized rats.

In anesthetized (chloralose and urethane), paralyzed and artificially ventilated rats, the neurons in the nucleus tractus solitarius (NTS) were chemically stimulated by microinjections of L-glutamate and the cerebral blood flow (CBF) was determined using a combination of labeled microspheres (either 57Co, 113Sn and 46Sc or 141Ce, 85Sr and 46Sc). Unilateral chemical stimulation of the NTS (n = 14) decreased CBF significantly in most brain areas. The decrease in CBF was not due to the decrease in arterial blood pressure (ABP) because the CBF of the whole cerebral cortex during the chemical stimulation of the NTS was significantly smaller (P less than 0.05) than the CBF during controlled hemorrhagic hypotension (n = 10). In another group of rats (n = 6), moderate hypertension was induced by blood transfusion. Unilateral chemical stimulation of the NTS in these rats decreased ABP but it remained within normotensive range. A significant (P less than 0.05) decrease in CBF (from 62 +/- 28 (mean +/- S.D.) to 48 +/- 23 ml.min-1.(100 g)-1) and increase in cerebrovascular resistance (from 1.9 +/- 1.2 to 2.6 +/- 1.2 mm Hg per [ml.min-1.(100 g)-1]) was observed in the whole cerebral cortex of these rats. Chemical stimulation of the NTS did not affect the reactivity of the cerebral vessels to hypercapnea (n = 5). These results suggest that the cell bodies within the NTS may play a role in the control of cerebral circulation.

Animals↗
PubMed1992

Microwave-stimulated chemical fixation of whole eyes.

BACKGROUND: Microwave-stimulated chemical fixation has been used successfully to rapidly prepare nonocular tissue for processing and paraffin embedding. METHOD: This same technique was adapted to fix whole eyes using a common domestic microwave oven. Histologic sections were compared with sections from globes that were fixed in a traditional manner. RESULTS: Histologic sections and histochemical and immunohistochemical staining of eyes treated with microwave-stimulated chemical fixation in 10% neutral-buffered formalin were comparable in quality to eyes fixed in 10% neutral-buffered formalin at room temperature for 48 hours. CONCLUSION: Because microwave irradiation accelerates the most time-consuming part of preparing whole eyes for light microscopy, the technique enhances laboratory efficiency. The technique is particularly well suited for ensuring adequate fixation of globes when histologic diagnosis is needed in less than 48 hours.

Animals↗
PubMed1991

Chemical stimulation of the rostral ventrolateral medullary pressor area decreases cerebral blood flow in anesthetized rats.

In urethane-anesthetized, paralyzed and artificially ventilated rats, the neurons in the rostral ventrolateral medullary pressor area (VLPA) were chemically stimulated by microinjections of L-glutamate (1.7-5.0 nmole in 100 nl of 0.9% sodium chloride solution) and the cerebral blood flow (CBF) was determined using a combination of labeled microspheres (57Co, 113Sn and 46Sc). In one group of rats (n = 11), unilateral chemical stimulation of the VLPA produced a significant (P less than 0.01) increase in arterial blood pressure (ABP), a significant (P less than 0.05) decrease in CBF, and a significant (P less than 0.01) increase in cerebrovascular resistance (CVR) in the cerebral cortex ipsilateral to the stimulated VLPA. The CBF was 52 +/- 3 (mean +/- S.E.M.) and 48 +/- 4 ml.min-1.(100 g)-1 before and during the chemical stimulation of VLPA; the CVR was 1.9 +/- 0.1 and 2.6 +/- 0.3 mmHg per ml.min-1.(100 g)-1 before and during the stimulation. In order to measure CBF at normotension, moderate hypotension was induced by controlled hemorrhage in another group of rats (n = 8). Unilateral chemical stimulation of the VLPA in these rats increased ABP but it remained within normotensive range. The CBFs of ipsilateral and contralateral cerebral cortices decreased significantly (P less than 0.05) from 57 +/- 14 to 41 +/- 9 and from 50 +/- 12 to 39 +/- 9 ml.min-1.(100 g)-1, respectively. The CVRs of ipsilateral and contralateral cortices increased significantly (P less than 0.05) from 2.6 +/- 0.6 to 3.5 +/- 0.8 and from 2.7 +/- 0.5 to 3.5 +/- 0.8 mmHg/[ml.min-1.(100 g)-1], respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia↗
PubMed1992

Feeding suppression elicited by electrical and chemical stimulations of monkey hypothalamus.

The effects of electrical (ES) and chemical stimulations of the hypothalamus were investigated in monkeys during bar-press feeding. ES elicited both prolonged and nonprolonged types of suppression of bar-press feeding in hungry animals. Prolonged type suppression persisted for greater than 1 min beyond one or more post-ES trials and was found after ES of the dorsomedial hypothalamus (DMH), the ventromedial hypothalamus (VMH), and the ventromedial part of the lateral hypothalamic area (LHA). Non-prolonged type suppression was observed only during ES at some sites of both in hypothalamic and extrahypothalamic areas. A microinjection of glutamate into the VMH and the DMH, but not into the LHA, was able to reproduce the ES-induced prolonged type suppression. In contrast, the ES of the LHA, but not the VMH and DMH, in a satiated state provoked feeding. The results, together with the previous findings, suggest that the neuronal inhibitory mechanism of feeding exists in the VMH and DMH, while both the neuronal facilitatory and axonal inhibitory mechanisms in the LHA are involved in the feeding regulation, and these mechanisms of the LHA are affected by the hunger/satiety state.

Animals↗
PubMed1991

Activation of brown adipose tissue thermogenesis by chemical stimulation of the hypothalamic supraoptic nucleus.

Glutamate microinjection (1 M, 250 nl) into the hypothalamic supraoptic nucleus (SON) stimulated heat production in brown adipose tissue (BAT) and caused a rapid and sustained increase in interscapular BAT and core temperatures in urethane-anaesthetized rats. This effect was blocked by intraperitoneal pretreatment with a sympathetic ganglionic blocker, chlorisondamine chloride (2.5 mg/kg), or a beta-adrenergic receptor blocker, propranolol (2.5 mg/kg), but not by prior hypophysectomy or intracerebroventricular pretreatment with specific receptor blockers to vasopressin (d(CH2)5[Tyr(Me)2]AVP, 5 micrograms) or oxytocin (d(CH2(5)[Tyr(Me)2,Thr4,Tyr-NH2(9)]OVT, 5 micrograms). The results demonstrate that stimulation of SON cells with glutamate elicits a non-vasopressinergic/non-oxytocinergic neural signal that can bring about a sympathetically-mediated increase in BAT thermogenesis. Heat production in BAT is an important mechanism of thermal protection during cold stimulation, and there is evidence that osmotic stimulation can influence thermoregulation. SON neurons play a major role in osmoregulation via release of the peptide hormones vasopressin and oxytocin. The present results suggest the possibility that apart from releasing peptide hormones for osmoregulation, SON neurons might be involved in mediating the effect of osmotic stimulation on thermoregulatory responses involved in thermal adaptation.

Adipose Tissue, Brown↗
PubMed1976

Effects of chemical stimulation of the mesolimbic dopamine system upon locomotor activity.

The effects of local injections of drugs into terminal areas of the mesolimbic dopamine system were investigated. Bilateral administration of dopamine, but not of noradrenaline and serotonin, into the nucleus accumbens of non-pretreated rats resulted in stimulation of locomotor activity. No clear or only minor effects were seen after injections of the dopamine metabolites 3-methoxytyramine, DOPAC and HVA and after injections of media with different pH and osmolality. d-Amphetamine proved more effective than dopamine in producing locomotor stimulation, whereas both stimulant and depressant effects were observed following injection of apomorphine into the nucleus accumbens. ET 495 and the noradrenaline agonists clonidine, phenylephrine and isoprenaline did not enhance locomotor activity, but theophylline was effective. Pretreatment with haloperidol, but not with clozapine, significantly reduced the effects of dopamine and theophylline. Locomotor stimulation was also found following bilateral administration of dopamine, d-amphetamine and apomorphine into the tuberculum olfactorium, whereas noradrenaline, serotonin and ET 495 produced no, or rather depressant effects. These results provide further evidence for an important role of the mesolimbic dopamine system with respect to locomotor activity.

Animals↗