Is sialic acid a promising marker for periodontal diseases?

OBJECTIVE: Periodontal diseases are inflammatory chronic infections. Sialic acid (SA) is an acute phase reactant by itself. The aim of this study is to investigate the relationship between salivary and serum SA levels and clinical parameters in different forms of periodontal diseases. SUBJECT AND METHODS: Systemically healthy subjects were included in the study; patients with chronic gingivitis (CG) (n = 10), chronic periodontitis (CP) (n = 10), and aggressive periodontitis (AgP) (n = 10), and ten volunteers with healthy periodontium as the control group. Total SA levels were determined by Warren's thiobarbituric acid method in whole saliva, parotis saliva, and serum samples of subjects before and 3 months after nonsurgical periodontal treatment. Full mouth clinical parameters including plaque index, gingival index, probing depth, and bleeding on probing were also recorded. RESULTS: Before treatment, in both periodontitis groups salivary and serum SA levels were higher than those of controls (P = 0.001). Both salivary and serum SA levels decreased significantly in the patient groups after treatment (P < 0.001). Multiple comparisons of baseline clinical parameters in all groups revealed significant differences (P = 0.001) and these parameters decreased significantly on the 90th day (P < 0.01). There were positive correlations between SA levels and periodontal indices of the CG, CP, and AgP groups (P < 0.05). CONCLUSION: Our results suggest that SA level in both saliva and serum may be a potentially useful marker to determine inflammatory changes and investigate different forms of periodontal diseases.

Plasma tissue factor levels and salivary tissue factor activities of periodontitis patients with and without cardiovascular disease.

The association between periodontal and cardiovascular disease has received considerable attention. Studies have demonstrated a higher incidence of atherosclerotic complications in patients with periodontal disease. Tissue factor (TF) has been known as a key initiator of the coagulation cascade, and the TF pathway is the primary physiological mechanism of initiation of blood coagulation. Recently, it has been shown that the circulating pool of TF in blood is associated with increased blood thrombogenicity in patients with coronary artery disease (CAD). Various tissues and saliva have been known to have TF activity. Consequently, the aim of this study was to investigate plasma TF levels and TF activity of saliva in periodontitis patients with and without diagnosed CAD. Twenty-six patients with a diagnosis of CAD and 26 systemically healthy patients were examined in the dental clinic, and the Community Periodontal Index Treatment Needs (CPITN) scores were recorded. Plasma TF levels were determined using commercially available ELISA kit. Salivary TF activities were determined according to Quick's one-stage method. Plasma TF levels were significantly increased in patients with CAD when compared with the control group. There was no difference in salivary TF activities between the 2 groups, but there was a strong and negative correlation between salivary TF activities and CPITN indexes in both groups. In order to determine the possible role of TF activity as a salivary marker in CAD and periodontitis and to fully understand the negative correlation between salivary TF activities and CPITN, TF activity of gingival crevicular fluid that may also affect saliva can be evaluated.

The effect of estrogen receptor agonists on pancreaticobiliary duct ligation induced experimental acute pancreatitis.

The 17ß-estradiol plays a role in physiology of pancreas and may protect it from inflammation. To examine the possible anti-inflammatory effects of 17ß-estadiol in pancreaticobiliary duct ligated (PBDL) acute pancreatitis (AP) model, and the underlying mechanism that 17ß-estradiol acts on, via evaluating the direct and the receptor related effects by using 17ß-estradiol, ER-α and -ß agonists. In the study both sexes of rats (n = 88) were used. Animals were divided into two groups as PBDL and PBDL + ovariectomized. ER-α agonist propyl-pyrazole-triol (PPT; 1 mg/kg/day), ER-ß agonist diarylpropionitrile (DPN; 1 mg/kg/day) and 17ß-estradiol (10 mg/kg/day) were administered to the groups for 3 days following AP induction. On the 3rd day, lung and pancreas tissues and serum samples were taken for malondialdehyde (MDA), glutathione (GSH), myeloperoxidase (MPO), superoxide dismutase (SOD) and interleukin (IL) assays, and histological analyses. In both tissues of male and female AP groups MPO, MDA, SOD levels were increased (P < 0.05 - 0.01) and GSH levels were decreased (P < 0.05). Pancreas and lung MDA and SOD levels were improved with all treatments in female, except lung MDA levels of PPT-treated ones, while lung MDA and SOD levels were improved by PPT and 17ß-estradiol in females and via PPT in males (P < 0.05 - 0.001). The increased MPO levels were inhibited with PPT in male pancreas and female lung and with 17ß-estradiol in female pancreas (P < 0.05). The increased pro-inflammatory ILs were declined by treatments (P < 0.05 - 0.001). 17ß-estradiol and ER-α and -ß agonists reduced oxidative pancreatic and pulmonary damage. Estrogen and agonists might have protective role in AP.

High dietary fructose does not exacerbate the detrimental consequences of high fat diet on basilar artery function.

The objective of the study was to determine the effects of a high fat (HF) diet alone or with high fructose (HF/F) on functional and structural changes in the basilar arteries and cardiovascular health parameters in rats. Male Sprague Dawley rats were fed either a HF (30%) or HF/F (30/40%) diet for 12 weeks. The basilar artery was cannulated in a pressurized system (90 cm H2O) and vascular responses to KCl (30 - 120 mM), endothelin (10(-11) - 10(-7) M), acetylcholine (ACh) (10(-10) - 10(-4) M), diethylamine (DEA)-NONO-ate (10(-10) - 10(-4) M), and papaverine (10(-10) - 10(-4) M) were evaluated. Rats were also monitored for food intake, body weight, blood lipids, blood pressure, and heart rate. At death, asymmetrical dimethyl arginine level (ADMA) and leptin were assayed in serum. Although there was no significant difference in weight gain and food intake, HF and HF/F diets increased body fat composition and decreased the lean mass. HF/F diet accelerated the development of dyslipidemia. Although resting blood pressure remained unchanged, stress caused a significant elevation in blood pressure and a modest increase in heart rate in HF fed rats. Both HF and HF/F diet resulted in decreased response to endothelium-dependent and -independent relaxation, whereas increased basilar artery wall thickness was observed only in HF group. Serum leptin levels positively correlated with wall thickness. Moreover serum ADMA was increased and eNOS immunofluorescence was significantly decreased with both diets. These data suggest that the presence of high fructose in a HF diet does not exacerbate the detrimental consequences of a HF diet on basilar artery function.

Effect of primary sludge fermentation products on mass balance for biological treatment.

Laboratory batch experiments were conducted at 20 degrees C to investigate the potential of primary sludge fermentation for the generation of readily biodegradable substrate and to evaluate the effect of fermentation products on mass balance for organic carbon, nitrogen and phosphorus, emphasizing COD fractionation. Fermentation converted between 18 to 30% of the initial volatile suspended solids in the sludge into soluble biodegradable COD. The volatile fatty fraction of the soluble COD was approximately 85% after the fermentation process. The average volatile fatty acid composition in fermentation involved 50% acetic acid, 33% propionic acid, 9% butyric acid and 8% valeric acid, indicating that the most important volatile fatty acid obtained during the biological fermentation process was acetate with more than half of total VFA concentration, which is one of the most important carbon sources for denitrification and biological nutrient removal processes. The recoverable fraction of the fermented sludge supernatant could potentially increase the readily biodegradable COD content of the primary effluent by 5%, together with a potential increase of the soluble nitrogen and phosphorus content by 2%.

Anti-inflammatory effects of nesfatin-1 in rats with acetic acid - induced colitis and underlying mechanisms.

Mucosal balance impairment, bacterial over-proliferation, cytokines, inflammatory mediators are known as responsible for inflammatory bowel disease. Besides known anorexigenic, neuroprotective, and anti-apoptotic effects, the major effect of nesfatin-1 on colitis is unknown. Our aim was to investigate the possible anti-inflammatory effects of nesfatin-1 in acetic acid induced colitis model and potential underlying mechanisms. Male Spraque-Dawley rats were anesthetized by intraperitoneal ketamine (100 mg/kg) and chlorpromazine (0.75 mg/kg). For nesfatin-1 and antagonist applications some of the rats were intracerebroventricularly (i.c.v.) cannulated. In colitis group, intrarectally (i.r.) 4% acetic acid solution (1 ml) and 10 minutes later i.c.v. nesfatin-1 (0.05 µg/5 µl) or vehicle (5 µl) were administered. Treatments continued for 3 days. In control group, physiological saline solution was used intrarectally. To identify the underlying effective mechanism of nesfatin-1, rats were divided into 3 subgroups, 5 minutes following colitis induction; i.c.v. atosiban (oxytocin receptor antagonist), SHU9119 (melanocortin receptor antagonist) or GHSR-1a antagonist (ghrelin receptor antagonist) were administered, 5 minutes later nesfatin-1 was administered for 3 days. On the fourth day, rats were decapitated, and colon tissues were sampled. Macroscopic and microscopic damage scores of distal colon, and colonic tissue malondialdehyde, glutathione, myeloperoxidase, superoxide dismutase, catalase, luminol and lucigenin chemiluminescence measurements were analysed. The increased myeloperoxidase activity, malondialdehyde levels, luminol and lucigenin chemiluminescence measurements, macroscopic and microscopic damage scores with colitis induction (P < 0.05 - 0.001) were decreased with nesfatin-1 treatment (P < 0.05 - 0.001). Nesfatin-1 may show this effect by inhibiting neutrophil infiltration through tissues and by decreasing formation of free oxygen radicals. Atosiban and GHSR-1a administration alleviated the protective effect of nesfatin-1 from microscopic and oxidant damage parameters and lipid peroxidation (P < 0.05 - 0.001). The results of the study suggest that nesfatin-1 had a protective effect from colitis induction, and the anti-inflammatory and antioxidant effects of nesfatin-1 on colitis might occur via oxytocin and ghrelin receptors.

Edaravone ameliorates the adverse effects of valproic acid toxicity in small intestine.

Valproic acid (VPA) is a drug used for the treatment of epilepsy, bipolar psychiatric disorders, and migraine. Previous studies have reported an increased generation of reactive oxygen species and oxidative stress in the toxic mechanism of VPA. Edaravone, a free radical scavenger for clinical use, can quench free radical reaction by trapping a variety of free radical species. In this study, effect of edaravone on some small intestine biochemical parameters in VPA-induced toxicity was investigated. Thirty seven Sprague Dawley female rats were randomly divided into four groups. The groups include control group, edaravone (30 mg(-1) kg(-1) day(-1)) given group, VPA (0.5 g(-1) kg(-1) day(-1)) given group, VPA + edaravone (in same dose) given group. Edaravone and VPA were given intraperitoneally for 7 days. Biochemical parameters such as malondialdehyde, as an index of lipid peroxidation(LPO), sialic acid (SA), glutathione levels and glutathione peroxidase, glutathione-S-transferase, superoxide dismutase, catalase, myeloperoxidase, alkaline phosphatase (ALP), and tissue factor (TF) activities were determined in small intestine samples by colorimetric methods. Decreased small intestine antioxidant enzyme activities, increased LPO and SA levels, and increased activities of ALP and TF were detected in the VPA group. Based on our results edaravone may be suggested to reverse the oxidative stress and inflammation due to VPA-induced small intestine toxicity.

Modulation of the pressor response elicited by carbachol and electrical stimulation of the amygdala by muscarinic antagonists in conscious rats.

1. The nature of the muscarinic receptor involved in mediating cardiovascular changes caused by unilateral microinjection of carbachol (5 nmol) into, and electrical stimulation (200-300 microA) of, the amygdaloid complex was investigated in conscious, unrestrained female Sprague-Dawley rats. 2. Unilateral microinjection of carbachol (5 nmol; n = 6) and electrical stimulation (200-300 microA, 80 Hz, 30 s; n = 4) caused a significant rise in blood pressure of 21 +/- 4 mmHg and 25 +/- 5 mmHg, respectively. These changes were associated with no overall effect on heart rate. The effects of electrical stimulation were found to be repeatable. 3. Pretreatment i.c.v. with pirenzepine (5-20 mmol; n = 6-7 for each dose), dose-dependently inhibited the rise in blood pressure induced by carbachol, whereas AF-DX 116 (100 nmol; n = 6) failed to have any effect on the carbachol-induced pressure response. Neither antagonist alone had any effect on resting baseline variables. 4. Unilateral microinjections of atropine sulphate (1-100 nmol; n = 4-6 for each dose), pirenzepine (0.03-10 nmol; n = 4 for each dose) or AF-DX 116 (10-60 nmol; n = 4-5 for each dose), into the amygdala, dose-dependently inhibited the rise in blood pressure caused by electrical stimulation (200-300 microA). The ID50 values were 1.05, 0.23 and 39.5 nmol, respectively. Although pirenzepine seemed to be more potent than atropine, this difference was not significant. 5. It is concluded that the rise in blood pressure elicited by unilateral microinjection of carbachol into, or electrical stimulation of, the amygdaloid complex is mediated by M1-muscarinic receptors.

The protective effect of 5-HT3 receptor antagonist in thyrotropin releasing hormone-induced gastric lesions.

The present study examined 1) oxidative stress and gastric lesions induced by thyrotropin releasing hormone (TRH) 2) The effect of a 5-hydroxytryptamine3 (5-HT3) receptor antagonist, ICS 205930 on protective effect of calcitonin on gastric lesions produced by TRH. Calcitonin (5 micrograms/10 microliter) was injected i.c.v. 10 min before TRH (10 micrograms/10 microliter, i.c.v.) injection or ICS 0.5 mg/kg, (i.p.) was given 60 min prior to calcitonin or TRH to rats. Ulcer index, lipid peroxidation (LP) and glutathione (GSH) levels were quantified 3 h after TRH injection in the stomach, liver and brain. TRH caused mucosal lesions (UI: 10.0 +/- 2.0 mm) without changing gastric GSH and LP. JCS did not alter the protective effect of calcitonin against TRH-induced lesions but attenuated. TRH-induced lesion formation. The oxidative effects of calcitonin or ICS were similar to TRH but both drugs attenuated gastric lesion formation. Hence, oxidative changes in tissues studied are not directly involved in TRH-induced lesions.

Nicardipine reduces the levels of leukotriene C4 and prostaglandin E2, following different ischemic periods in rat brain tissue.

Ischemic depolarization of nerve membranes is associated with a rapid influx of calcium into the cell, resulting in production of arachidonic acid (AA) metabolites. These metabolites, particularly leukotriene C4 (LTC4) have a very potent vasoconstrictor effect on cerebral arteries inducing vasogenic edema that may damage the ischemic penumbra. Calcium antagonists are assumed to prevent or reduce metabolic disturbances associated with ischemia. In this study, after developing an experimental animal model simulating the concept of the ischemic penumbra in the rat, the levels of LTC4 and prostaglandin E2 (PGE2) produced in the forebrain following different ischemic periods, such as 4th, 15th, 60th and 240th min were measured by a bioassay method, including 6 rats for each ischemic group. Then the effect of the 1-4 dihydropyridine nicardipine (1 mg/kg) on these mediators was investigated by giving it to the rat 30 min before the development of the ischemic model in each corresponding group (n = 6). We showed that nicardipine significantly reduced the high levels of LTC4 and PGE2 in the 4th min and 4th h of cerebral ischemia (p less than 0.005, p less than 0.0005). So it may be concluded that institution of nicardipine may be helpful in protecting the ischemic penumbra during the early hours of cerebral ischemia.

The alterations of leukotriene C4 and prostaglandin E2 levels following different ischemic periods in rat brain tissue.

Leukotrienes and prostaglandins are formed from arachidonic acid by activation of local phospholipases in pathological conditions such as cerebral ischemia, subarachnoid hemorrhage, cerebral tumors and seizures. These mediators, especially leukotrienes have a very potent vasoconstrictor effect on cerebral arteries. Experimental studies have shown that this effect, by increasing vascular permeability causes vasogenic edema that contributes to the ischemic penumbra. In this study, after developing an experimental animal model simulating the concept of ischemic penumbra in the rat, the levels of leukotriene C and prostaglandin E2 produced in the forebrain were measured and the effects of these mediators in prolonged ischemia were investigated. The results, in the first 4 min of ischemia, showed that the arachidonic acid metabolites, particularly, leukotriene C4, reached a peak in the ischemic cerebral tissue in association with leukocyte accumulation. Later in the 15th min, significant decreases in leukotriene C4 and prostaglandin E2 levels were seen. In the 1st and 4th h, probably due to the stimulation of the relevant enzymes by free oxygen radicals in the ischemic tissue; the levels increase again, returning to control values by the 12th h. It is concluded that the use of lipoxygenase inhibitors and free radical scavengers may be helpful to limit the infarct area in the first 4 h of ischemia.

Reversal of hemorrhagic shock in rats by oxotremorine: the role of muscarinic and nicotinic receptors, and AV3V region.

In an experimental model of hemorrhagic shock resulting in the death of almost all rats within 20-30 min, centrally active cholinomimetic drugs are reported to induce a prompt, sustained and dose-dependent improvement in blood pressure and survival rate claimed to be due to nicotinic, but not muscarinic actions. In the present study, cholinergic receptor agonist, oxotremorine (50 micrograms/kg, i.v.) increased mean arterial pressure (from 22 +/- 1 to 123 +/- 3 mm Hg) and 60 min-survival rate (from 0% to 92%) in rats bled to hypovolemic shock. Atropine (2 mg/kg, i.v.) pretreatment inhibited the pressor effect of oxotremorine significantly, but did not modify its effect on survival rate. On the other hand, pretreatment with mecamylamine (50 micrograms, i.c.v.) almost abolished the reduction in mortality rate, but inhibited the pressor effect of oxotremorine, partially. These results indicate that oxotremorine-induced pressor response and decrease in mortality in rats with severe hemorrhagic shock are primarily mediated via central muscarinic and nicotinic receptors, respectively. AV3V region was previously reported to be involved in pressor and natriuretic effects of i.c.v. carbachol in normotensive rats. In the present study, the electrolytic lesions of AV3V region significantly inhibited oxotremorine-induced increases in both blood pressure and survival rate in rats subjected to hemorrhagic shock. These findings indicate that AV3V region plays a major role in cholinergic cardiovascular control in hypotensive animals as well as normotensives.

The role of amygdala and hypothalamus in GABAA antagonist bicuculline-induced cardiovascular responses in conscious rats.

gamma-Aminobutyric acid (GABA) is known to play an important role in the central control of cardiovascular functions. GABAergic agonists and antagonists elicit blood pressure and heart rate changes when injected into the brain. It was demonstrated here that bicuculline methiodide (BMI), a GABAA antagonist, caused dose-dependent increases in both blood pressure and heart rate in conscious rats when injected intracerebroventricularly. The roles of the central nucleus of the amygdala (CeA), the paraventricular nucleus (PVN) and the dorsomedial nucleus (DMH) of the hypothalamus in BMI-induced blood pressure and heart rate changes were investigated in this study. The pressor effect of BMI was significantly attenuated by the electrolytic ablation of DMH and PVN, whereas it was only slightly, but insignificantly reduced by CeA lesions. The microinjection of BMI into the DMH and the PVN elicited significant pressor and tachycardic responses whereas only a slight increase was observed in rats injected BMI into the CeA. The BMI-induced increases in both blood pressure and heart rate were more prominent when given into the DMH. These results indicate that the DMH plays an important role in GABAergic control of cardiovascular functions. The PVN and CeA seem to have a minor part in this respect.

Carbachol-induced pressor responses and muscarinic M1 receptors in the central nucleus of amygdala in conscious rats.

The type of muscarinic receptor in the central nucleus of the amygdala that mediates the carbachol-evoked pressor responses was investigated in conscious unrestraint Sprague-Dawley rats. Carbachol (100 ng) injected into the lateral cerebral ventricle caused a significant rise in blood pressure of 31.8+/-4.5 mmHg and a decrease in heart rate of 80.0+/-12.2 beats/min. Pirenzepine (10-75 nmol) injected into the central nucleus of the amygdala inhibited carbachol-induced pressor responses dose-dependently. The bradycardic response to carbachol was also inhibited by pirenzepine, but no dose-dependency was observed. Injection of pirenzepine into the basolateral amygdala at a dose (50 nmol) that inhibited carbachol-induced changes in mean arterial pressure and heart rate when injected into the central nucleus of the amygdala failed to exert any inhibition. Methoctramine at a dose of 50 nmol injected into both the central nucleus of the amygdala and the basolateral amygdala did not cause any significant alteration in the responses. These results indicate that muscarinic M1 receptors in the central nucleus of the amygdala are involved in cardiovascular regulation mediated by central cholinergic pathways.

Central muscarinic M2 cholinoceptors involved in cholinergic hypertension.

Cholinomimetic agents increase blood pressure and heart rate via central muscarinic cholinoceptors in various species. It was reported that i.c.v. injection of the muscarinic M1 and M3 cholinoceptor selective antagonist, 4-DAMP (4-diphenylacetoxy-N-methyl-piperidine methiodide), inhibited the pressor response to physostigmine, while the M1 selective antagonist, pirenzepine, was ineffective. In the present study, the involvement of muscarinic M2 cholinoceptors in central cholinergic hypertension and tachycardia was investigated. Physostigmine (10-80 micrograms/kg i.v.), a cholinesterase inhibitor, and oxotremorine (20-40 micrograms/kg i.v.), a direct muscarinic cholinoceptor agonist, caused a dose-dependent increase in blood pressure. Additionally, physostigmine induced dose-dependent tachycardiac responses. I.c.v. administration of the muscarinic M2 cholinoceptor antagonists, AF-DX 116 and methoctramine, inhibited both physostigmine (60 micrograms/kg) and oxotremorine (20 micrograms/kg)-induced pressor responses at their lower doses used in this study (100 nmol/rat and 10 nmol/rat, respectively). These findings indicate the partial involvement of postsynaptic muscarinic M2 cholinoceptors. The higher doses of the antagonists (AF-DX 116,300 nmol/rat and methoctramine 30 nmol/rat) potentiated the blood pressure increase due to physostigmine but did not affect that due to oxotremorine. The physostigmine-induced tachycardiac responses were influenced similarly by these antagonists. These results suggest the presence and tonic influence of presynaptic inhibitory muscarinic M2 cholinoceptors.

Potentiation of the morphine-induced respiratory rate depression by captopril.

The effects of morphine and captopril, an angiotensin-converting enzyme inhibitor, on respiratory frequency have been investigated in non-anesthetized mice. Morphine (10.0 mg/kg) reduced the respiratory frequency which gradually returned to the control level 2 h after the injection. The same dose of morphine when given together with captopril (0.1 and 1.0 mg/kg), caused a similar reduction in respiratory rate. This respiratory depression however, persisted until the end of the observation period. Similar results were obtained with the same dose of morphine in mice pretreated with captopril. The minimal dose of morphine reducing respiratory frequency (3.0 mg/kg), when given to the mice pretreated with captopril (0.1 mg/kg) caused a significant reduction in respiratory frequency and this effect was equal to that obtained with 10.0 mg/kg morphine alone. The results are discussed from the point of the possible inhibitory effect of captopril on the enkephalin degrading enzyme(s).

The role of nitric oxide in the reversal of hemorrhagic shock by oxotremorine.

In the present study, the effect of the nitric oxide synthase inhibitor, N(G)-nitro-L-arginine methylester (L-NAME), on the antishock actions of oxotremorine was investigated in rats subjected to hemorrhagic shock under urethane anesthesia. L-citrulline production in the AV3V region, as an indicator of nitric oxide (NO) synthesis, was assayed by high-performance liquid chromatography (HPLC) with fluorescent detection throughout the experiment. The rats were pretreated with either intravenous (i.v.) physiological saline or L-NAME (2.5 mg/kg) before bleeding. L-NAME potentiated the reversal of hypotension by oxotremorine (25 microg/kg, i.v.). However, oxotremorine either alone or in combination with L-NAME did not produce any significant change in 60-min survival rate at this low dose. Analysis of microdialysis samples collected from the AV3V region showed that L-citrulline concentration increased during bleeding and that this increase was abolished by L-NAME pretreatment. These results may suggest that nitric oxide production contributes to hypotension in rats bled to shock since nitric oxide levels in the AV3V region increased in response to bleeding and nitric oxide synthase (NOS) inhibition abolished this increase and potentiated the oxotremorine-induced reversal of hypotension.

The role of brain acetylcholine in GABAA receptor antagonist-induced blood-pressure changes in rat.

Previous experimental studies have shown that intracerebroventricular (i.c.v.) injection of the GABAA receptor antagonist, bicuculline methiodide, results in marked increases in blood pressure due to an increase in sympathetic nervous system activity. It is well recognized that the central cholinergic system is also involved in the regulation of blood pressure. In the present study, we examined the role of brain acetylcholine in the pressor response induced by bicuculline methiodide in conscious Sprague-Dawley rats. I.c.v. (0.05, 0.3 and 0.5 nmol) and intrahypothalamic (40 pmol) administration of bicuculline methiodide produced blood-pressure increases in a dose-dependent manner. Hemicholinium-3 was given i.c.v. 1 h prior to bicuculline methiodide. The depletion of brain acetylcholine was demonstrated by the suppression of physostigmine-induced pressor responses, but blood pressure increases in response to carbachol remained unchanged. The pressor responses to bicuculline methiodide in animals pre-treated with hemicholinium-3 were significantly higher than those seen in saline-pre-treated groups. Likewise, bicuculline methiodide, at a dose that did not alter blood pressure alone, caused pressor responses in rats pre-treated with the nicotinic receptor antagonist, mecamylamine, whereas the muscarinic receptor antagonist, atropine, was ineffective in this respect. In conclusion, it seems likely that endogenous brain acetylcholine has a modulator role on GABAA receptor-mediated blood-pressure control via nicotinic receptors.

Role of the AV3V region in the pressor responses induced by amygdala stimulation.

The role of the anteroventral third ventricle (AV3V) region in the pressor responses to carbachol injected into the lateral cerebral ventricle (i.c.v.), the electrical stimulation of and carbachol-induced stimulation of, the central nucleus of the amygdala were investigated in conscious, unrestrained Sprague-Dawley rats. I.c.v. and intra-amygdalar carbachol caused a significant rise in blood pressure of 22.9 +/- 2.8 and 16.8 +/- 2.2 mmHg, respectively. Electrical stimulation (1 ms, 80 Hz, 50-300 microA, for 30 s) of the central nucleus of amygdala also produced intensity-dependent pressor effects. Electrolytic lesion of the AV3V region abolished the pressor responses induced by carbachol and by electrical amygdala stimulation. The heart rate changes were also significantly inhibited in the AV3V-lesioned rats. These results indicate that the integrity of the AV3V region is essential for the central cholinergic cardiovascular changes induced by central amygdaloid nucleus stimulation.

Effect of muscimol on cholinomimetic-induced cardiovascular responses in rats.

Brain acetylcholine and gamma-aminobutyric acid (GABA) are both involved in the regulation of central cardiovascular control. Despite data from anatomical and electrophysiological experiments characterizing the interaction between central GABAergic and cholinergic neurotransmission, the potential significance of this interaction in central cardiovascular regulation remains unknown. The purpose of this study was to determine whether activation of GABA(A) receptors by intracerebroventricular or intrahypothalamic administration of muscimol affects the cholinergic agonist-induced cardiovascular responses. All experiments were performed in conscious, Sprague-Dawley rats instrumented with a guide cannula for drug injection and iliac arterial catheters for direct measurement of mean arterial pressure and heart rate. Administration of a cholinergic agonist, carbachol, either intracerebroventricularly or into the dorsomedial hypothalamic nucleus, produced a significant increase in mean arterial pressure, whereas injection of carbachol into the posterior hypothalamic nucleus caused a slight elevation in blood pressure. Pretreatment with muscimol 10 min before administration of carbachol prevented the carbachol-evoked blood pressure changes. On the other hand, carbachol produced variable changes in heart rate, depending on the site of injection. In [3H]quinuclydinyl benzilate binding experiments, muscimol did not displace the muscarinic radioligand from its binding sites, suggesting that it does not exert any direct antagonistic activity at muscarinic receptors. These results suggest that the dorsomedial hypothalamic nucleus is a potential site of action for microinjected carbachol and that the GABAergic system has an inhibitory influence on cholinergic neurons involved in blood pressure regulation.