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Biomedical subjects

L Olgart

Publications and source records attributed to L Olgart.

At least 37 records · Page 2Linked to original sources
PubMed1992

Activation of sympathetic fibres in the pulp by electrical stimulation of rat incisor teeth.

Previous studies of the sympathetic nerve supply of the rat mandibular incisor pulp have shown conflicting results. Here, the neurovascular control of the rat lower incisor pulp was investigated by stimulating the tooth crown and the cervical sympathetic trunk electrically and monitoring blood-flow changes in the pulp by laser Doppler flowmetry. In addition the presence of noradrenaline (NA) in the pulp and gingiva was examined biochemically in untreated and sympathectomized animals by high-performance liquid chromatography. The tissue concentrations of NA in the pulp were 11-fold greater than those of gingiva. Surgical sympathectomy significantly reduced the NA content in the pulp by 76%. Monopolar electrical stimulation of teeth (25-50 microA) for 1 min resulted in a frequency-dependent reduction followed by an increase in pulpal blood flow. At 16 Hz the reduction in blood flow was 65% and the subsequent increase was 9%. After intravenous administration of the alpha-adrenoceptor antagonist phentolamine, the stimulation-induced reduction in pulpal blood flow was diminished by 94% while the increase was significantly enhanced (from 9 to 40%). Infusion of the beta-adrenoceptor antagonists propranolol and timolol significantly reduced this increase in blood flow by 53 and 55%, respectively. Preganglionic sympathetic nerve stimulation also induced a frequency-dependent reduction followed by a slight increase in pulpal blood flow. This reduction in blood flow was almost abolished after alpha-adrenergic blockade and there was no subsequent increase. These findings suggest that there are sympathetic nerve fibres in rat incisor pulp and that they are activated upon monopolar electrical stimulation of teeth resulting in alpha- and beta-adrenoceptor mediated blood-flow responses.

Adrenergic Fibers↗
PubMed1992

Effects of autonomic reflexes on tooth pulp blood flow in man.

In 15 subjects, laser-Doppler flowmetry (LDF) was used to investigate whether the nervous control of pulpal blood flow (PBF) is affected by three tests known to excite the sympathetic nervous system. For comparison, skin blood flow was similarly recorded. Dynamic exercise (bicycle ergometer, 5 min, 90-100 W) in eight subjects was accompanied by a rise in PBF. PBF was increased by the cold pressor test (2 min) in eight subjects, while in five the flow decreased or remained unaffected. The isometric hand grip (2 min, 30% MVC) and the subsequent muscle ischaemia (2 min) led to a rise in PBF in two subjects and a fall in four. Following unilateral anesthesia of the mandibular nerve, PBF in five subjects became unresponsive to dynamic exercise or the cold pressor test, indicating pressure autoregulation. All three tests triggered increases in mean arterial pressure (MAP) and heart rate (HR). Skin blood flow usually increased in response to the tests, but could also decrease, and often changed in a direction opposite to that of PBF. It is concluded that the circulation of blood in the human tooth is affected by evoked changes in autonomic nerve activity, involving activation of both vasodilator and vasoconstrictor nerves to vessels serving the tooth.

Adult↗
PubMed1991

Involvement of afferent nerves in pulpal blood-flow reactions in response to clinical and experimental procedures in the cat.

A unilateral resection of the mandibular nerve (n = 20) was made 10-14 days before investigation of the contribution of afferent nerves in vasodilator reactions in the dental pulp. Lower canine teeth were subjected to various stimuli and pulp blood-flow responses monitored by laser Doppler flowmetry. An absence of response to bipolar electrical (5 impulses, 50 microA, 5 ms, 2 Hz) stimulation on the tooth surface was used to demonstrate a successful chronic nerve lesion. Local application of capsaicin (10(-4) M) in a deep dentinal cavity induced a long-lasting increase in pulpal blood flow in control teeth only. Bradykinin (10(-3) M) induced significantly larger responses in control than in denervated teeth (58.3 +/- 9.8% and 24.5 +/- 4.9%, respectively, p less than 0.005, n = 8); in addition, the onset was slower and the duration of the response significantly (60%) shorter than in control teeth. Intermittent grinding of surface dentine instantly increased flow in control teeth by 53.0 +/- 12.5% (n = 12) whereas in denervated teeth the response was delayed and significantly (70%) smaller. Deeper preparation produced responses of similar magnitude in control and denervated teeth (69 and 50%, respectively) but the onset was delayed in denervated teeth. Low-intensity ultrasonic stimulation caused vasodilation in intact teeth (38% increase) but had no effect in denervated teeth. This effect was abolished after local anaesthetic (mepivacaine) injection. Sympathectomy (n = 3) did not influence stimulation-induced blood-flow responses in the dental pulp.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Topical↗
PubMed1991

Effects of angiotensin II on blood flow in rat submandibular gland.

The effect of angiotensin II (Ang II) was studied on blood flow in the submandibular gland and tongue in male rats. Blood flow changes were determined with laser Doppler flowmetry and Ang II was infused into the common carotid artery before and after i.v. doses (18 nmol kg-1) of the angiotensin II antagonist saralasin. Angiotensin II (10-60 pmol min-1) dose-dependently increased blood pressure and tongue blood flow, whereas glandular blood flow decreased at all of the doses used. After saralasin administration the angiotensin II effects on blood pressure, tongue and glandular blood flow were significantly diminished (glandular blood flow reduction was diminished from 29%-3%, P less than 0.005, n = 9). However, the responsiveness of these 3 parameters to local infusions with noradrenaline (0.75-3.0 pmol min-1) was unaffected by saralasin. The dose of saralasin used in the present study did not affect any of the parameters on it's own. Our results show that vascular receptors sensitive to angiotensin II operate in the submandibular gland but not in the tongue.

Angiotensin II↗
PubMed1989

The enhancement of carbachol-induced salivary secretion by VIP and CGRP in rat parotid gland is mimicked by forskolin.

Low doses of vasoactive intestinal polypeptide (VIP) and calcitonin gene-related peptide (CGRP) have been shown to augment the salivary volume secretion evoked by muscarinic receptor agonists or substance P (SP) in rat parotid gland. Since VIP and CGRP are known to activate adenylate cyclase, we have studied whether forskolin, which directly activates this enzyme, can mimic the effects of these peptides on salivary secretion from the parotid gland in anaesthetized (Inactin 0.5 g kg-1 i.p.) rats. We have also studied the effect of the secretagogues and peptides on glandular blood flow as revealed by the laser Doppler technique. Carbachol (5 nmol kg-1) and SP (185 pmol kg-1) injected i.v. caused a transient increase in parotid blood flow and a decrease in systematic blood pressure concomitant with a salivary secretion of 3.3 +/- 0.3 mg (n = 22) and 18.7 +/- 1.9 mg (n = 25) respectively. VIP (150 pmol kg-1) and CGRP (25 pmol kg-1) also caused a transient increase in glandular blood flow concomitant with a decrease in systemic blood pressure, but no salivary secretion. The glandular blood flow increased by 166 +/- 5% and 43 +/- 11% for VIP and CGRP respectively. When carbachol was given 20 s after the injection of VIP or CGRP, the secretory response was increased by about 250% and 60% respectively. The adenylate cyclase stimulator forskolin (2.5 pmol kg-1) produced the same type of response regarding blood flow and systemic blood pressure as VIP and CGRP and potentiated the salivary secretion evoked by carbachol (5 nmol kg-1) by about 100%.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Intradental nerve activity and jaw-opening reflex in response to mechanical deformation of cat teeth.

Mechanical stress was applied to canine teeth in anaesthetized cats to excite intradental A-fibres and to produce digastric muscle EMG responses. Activity in the intradental sensory units was recorded by two electrodes, one inserted in a dentinal cavity, the other in contact with the gingival sulcus. A pneumatically driven piston was used to cause a mechanical stress (10-150 N) on the stabilized tooth crown for 30 s, with instantaneous onset and release. Application of a load of 30 N produced a momentary burst of impulses in 2 of 12 teeth; 8 out of 10 teeth responded when 150 N was used. Digastric EMG responses were obtained at and above 60 N. Removal of the coronal pulp or cooling of the tooth crown with ethyl chloride abolished this reflex, whereas percussion of the tooth still produced a digastric response. Our results suggest that load-induced deformation of teeth activates intradental sensory mechanisms and a reflex withdrawal reaction unrelated to periodontal stimulation.

Animals↗
PubMed1988

Non-adrenergic, non-cholinergic salivary secretion in the ferret.

Secretion of parotid and submandibular saliva evoked by electrical stimulation of the parasympathetic nerves occurred in the presence of adrenergic and cholinergic blocking agents. The 'atropine-resistant' response amounted to about 30% in the submandibular gland and to about 5% in the parotid gland as compared to the response before administration of antimuscarinic agents. The 'atropine-resistant' secretion was found at relatively high frequencies, and the latency between the start of the stimulation and the onset of secretion was long. Upon long-lasting stimulation the 'atropine-resistant' secretion decreased rapidly and markedly. The tachykinins substance P (SP) and substance K, injected I.V., evoked flow of saliva from both glands. Given singly, exogenous vasoactive intestinal peptide (VIP) caused no salivary flow. However, it enhanced the tachykinin-evoked secretory response. The response to SP was also enhanced when I.V. injections of this peptide were combined with nerve stimulation, even at subthreshold frequencies for secretion, in the presence of the autonomic receptor blockers. Both tachykinins and VIP are putative transmitters involved in mediating the 'atropine-resistant' secretory response.

Animals↗
PubMed1987

Vasodilatory effects and coexistence of calcitonin gene-related peptide (CGRP) and substance P in sensory nerves of cat dental pulp.

Substance P (SP)- and calcitonin gene-related peptide (CGRP)-immunoreactivity (-IR) were localized by immunohistochemistry in the same nerve cell bodies in the trigeminal ganglia as well as in nerve terminals of the dental pulp. The distribution of SP- and CGRP-IR nerves were identical in the dental pulp and mainly associated with blood vessels. The level of CGRP-IR in the dental pulp, as measured by radio-immunoassay (RIA), was 1.4 +/- 0.2 pmol g-1 wet wt, which is in the same range as that found for substance P. Local intra-arterial infusion of synthetic CGRP and substance P produced vasodilatation in the dental pulp as measured by both laser Doppler flowmetry and an 125I clearance technique. The CGRP was effective as a vasodilator when infused in the femtomole per minute range, and SP in the picomole range. The effect of CGRP (50 fmol min-1) was 10 times larger when given after SP (15 pmol min-1) than before it. Since the two peptides coexist in the same neurons, it is suggested that they both contribute to the vasodilation seen upon antidromic stimulation of sensory nerves.

Animals↗
PubMed1987

Blood flow changes in the dental pulp of the cat and rat measured simultaneously by laser Doppler flowmetry and local 125I clearance.

Blood flow changes in the dental pulp of lower canine teeth of mature cats and incisors of mature rats were investigated with simultaneous laser Doppler flowmetry and local 125I-clearance (wash-out) during electrical sympathetic stimulation, efferent stimulation of n. alveolaris inferior (IAN) (cats) and i.a. infusions of substance P (SP) (cats). Stimulation (1-4 Hz, 4 V., 1.5 ms) of the cervical sympathetic trunk produced frequency-dependent decreases in both laser Doppler output and disappearance rate of iodine tracer from the dental pulp. For the effects of sympathetic stimulation, the correlation (r2) between the results obtained by the two methods was 0.89 (12 observations, six animals). Blood flow measurements by both methods were increased following i.a. infusions of SP (r2 = 0.64, six observations, three animals). However, upon stimulation of IAN (10 Hz 10 V, 5 ms) the laser Doppler flow values showed an increase while the local 125I clearance rate was unaffected or even decreased. The discrepancy between the results obtained following IAN stimulation indicates that the two methods reflect blood flow changes in different parts of the pulpal vascular bed and that the flow is unevenly distributed to these parts during antidromic IAN stimulation. The laser Doppler flowmetry seems to reflect the total blood flow in the coronal pulp and therefore this non-invasive method may be useful for monitoring blood flow changes in the tooth.

Animals↗
PubMed1986

Complementary action of substance P and vasoactive intestinal peptide on the rat parotid secretion.

Augmentation of the rat parotid salivary secretion to intravenous injections of substance P (SP) occurred when SP was combined with vasoactive intestinal peptide (VIP), or stimulation of the auriculo-temporal nerve in the presence of atropine and the adrenergic blockers, dihydroergotamine and propranolol. The largest increase was obtained when SP (0.5 micrograms kg-1) was used together with subthreshold doses of VIP (84% at 0.05 micrograms kg-1 and 105% at 0.5 micrograms kg-1) and low frequency stimulation (92% at 2 Hz and 97% at 5 Hz), which did not produce any salivary secretion by itself. There was no facilitated secretion when VIP and nerve stimulation were combined. Amylase output was much larger (250-500%) when SP was combined with nerve stimulation (0.5-5 Hz) or VIP (0.005-5 micrograms kg-1) than when SP was used alone. Similar results were obtained in rats where the auriculo-temporal nerve was stimulated during the early phase (24-90 h) of Wallerian degeneration, when the nerve-induced responses were seemingly completely blocked. Our results are consistent with the hypothesis that both VIP and SP contribute to the atropine-resistant parotid secretion, and that they have a complementary role in the rat parotid exocrine function.

Amylases↗
PubMed1986

Instrumentation of the curved root canal using filing or reaming technique--a clinical study of technical complications.

The technical results of two different techniques for instrumentation of root canals were evaluated. The study comprised 520 roots with various degree of curvature treated by supervised dental students using either a reaming of a filing technique. The results indicated that treatment complications were mainly associated with severely curved (greater than or equal to 35 degrees) canals (15-20% of the molars). Instrument breakage and lateral deviation from original canal curvature were more frequent with the reaming technique whereas overfilling and root perforation dominated with the filing technique. Loss in working length occurred with both techniques. It is suggested that the frequency of complications during instrumentation of curved canals might be diminished if files are used for the enlargement of the canal and reamers are used for the final shaping of the apical part.

Adult↗
PubMed1984

The effect of some metal ions on the intradental sensory nerves of the cat.

Intradental nerve activity from canine teeth of anesthetized cats was recorded during the application of different metal ion solutions in a dentinal cavity. The application of Ag2+, Ca2+, Cd2+, Cr3+, Hg2+, Mg2+, Mn2+, Ni2+, Pb2+, Sn2+, and Zn2+ reduced the nerve activity induced by NaCl 0.76 M and compound 48/80. The application of Cu2+ and Co2+ excited the intradental sensory nerves.

Action Potentials↗
PubMed1983

Morphine inhibits substance P release from peripheral sensory nerve endings.

Tissue levels of substance P (SP) were determined by radioimmunoassay in cat dental pulps after unilateral electrical stimulation of the inferior alveolar nerve. Nerve stimulation (10 V, 10 Hz, 5 ms for 3 min) reduced the SP level at the stimulated side by approximately 40%, indicating a release of SP. Stimulation performed after infusion of morphine (0.3 mg/kg/min, i.v.) for 10 min did not reduce the pulpal SP-level. Naloxone (3 mg/kg, i.v.) administered immediately before the morphine infusion in three experiments, did not influence the effect of morphine on pulpal SP levels after nerve stimulation. This may indicate an action of morphine on a naloxone-insensitive receptor type. Morphine in the dosage used did not influence the intradental sensory nerve conductivity. The results indicate that morphine is able to inhibit stimulus evoked release of SP from peripheral endings of primary afferent neurons.

Animals↗