Lack of pressor effect of dopamine in the pentobarbital-anesthetized rat

The blood pressure and heart rate responses to intravenous dopamine infusion at 2.5, 5.0 and 10.0 micrograms.min-1 X 100 g-1 were studied in conscious and pentobarbital-anesthetized Sprague-Dawley rats. In the conscious rats, dopamine caused a significant dose-related increase in the mean arterial blood pressure which was abolished in the anesthetized rats. The heart rate increased significantly only at the highest dose infused. The responses to equipressor doses of noradrenaline (40 ng.min-1 X 100 g-1) and phenylephrine (1.0 micrograms.min-1 X 100 g-1) were also suppressed in the anesthetized rats. The results suggest that pentobarbital anesthesia depresses the blood pressure response to dopamine infusion in the rat through a depression of activation of alpha-adrenoceptors.     

Some species differences in cardiovascular responses to intravenously injected leucine-enkephalin

Summary Studies were conducted to determine the cardiovascular responses to leucine-enkephalin (L-enk) in three different species of animals; rabbit, dog and monkey. All animals were anesthetized with pentobarbital sodium after sedation with ketamine. Mean blood pressure (MBP) and heart rate (HR) were simultaneously monitored. The pressor and HR responses to bilateral carotid occlusion (BCO) were determined before injection of L-enk. Increased MBP and HR due to BCO in monkey were significantly greater than in the other two animal groups. Following i.v. injection of L-enk (5–30 g/kg), a significant fall in MBP occurred in all groups in a dose-dependent manner; however, the time course of changes in MBP in rabbits was significantly shorter than that in the other animal groups. Significant in HR after the injection of L-enk occurred in rabbits and dogs, whereas increases in HR occurred in monkeys. These results show that some cardiovascular responses to L-enk may be species dependent. These different cardiovascular responses to L-enk may be at least partly related to species differences in baroreceptor reflex sensitivity.     

Role of peripheral chemoreceptors in response to smoke-induced apnea vs tracheal occlusion

Summary Reflex autonomic changes which occur after cigarette smoke enters the upper airways are partially due to peripheral chemoreceptor stimulation. Chemoreceptor denervation attenuates but does not abolish smoke induced bradycardia. Denervation nearly abolishes bradycardia induced by tracheal occlusion. Hypertension accompanies smoke induced apnea but does not occur during tracheal occlusion.Acknowledgments. This study was supported by Oral Roberts University research funds.     

Molecular forms of dopamine beta-hydroxylase in rat superior cervical ganglion and adrenal gland

Summary Dopamine beta-hydroxylase (DBH) enzyme activity was associated in rat superior cervical ganglion with tetrameric DBH-A (294,000 D) and dimeric DBH-B (147,000 D) and in rat adrenal gland with DBH-A and a novel molecular form of DBH, defined as DBH-C, with a molecular weight of 125,000 D. Pretreatment of the rats with cycloheximide markedly reduced DBH activity without altering the molecular heterogeneity.     

The effect of X-irradiation on the amount of dopamine in corpus striatum of the rat

Summary The effect of ionizing radiation on the amount of dopamine in corpus striatum was investigated in rats exposed to 650 or 850 R of X-rays. The amount of dopamine in the corpus striatum was measured fluorimetrically in various periods of time after irradiation. It was found that, irrespective of the dose applied, the ionizing radiation caused a significant depletion of dopamine in the striatum.     

Spontaneous morphine withdrawal from the rat spinal cord

Summary A characteristic and reproducible sign of narcotic withdrawal is the naloxone induced increase in arterial pressure. In morphine-dependent rats allowed to undergo spontaneous withdrawal (6–24 h) and then transected at the spinal C-1 level, arterial pressure was maintained at a significantly higher level than either spinal-transected nondependent controls or morphine-dependent, spinal-transected rats pithed from C-1 to L-4. These findings indicate that the morphine-dependent spinal cord, independent of supraspinal influences, is able to exhibit an autonomic component of spontaneous withdrawal.This study was supported by the Medical Research Service of the Veterans Administration. A preliminary report of aspects of this work appeared in Soc. Neurosci. Abs.10 (1984) 1113.     

The effect of x-irradiation on the amount of dopamine in corpus striatum of the rat.

The effect of ionizing radiation on the amount of dopamine in corpus striatum was investigated in rats exposed to 650 or 850 R of X-rays. The amount of dopamine in the corpus striatum was measured fluorimetrically in various periods of time after irradiation. It was found that, irrespective of the dose applied, the ionizing radiation caused a significant depletion of dopamine in the striatum.     

The effect of nicotine on blood pressure in the genetically hypertensive mouse

Summary Mice genetically selected for high and low blood pressure were exposed to nicotine via a single injected dose or addition to drinking water for 52 weeks. In the acute study, the response of mice with high blood pressure was a statistically significant increase in blood pressure. In the chronic study the pattern of response to nicotine ingestion was similar for mice with high blood pressure and those with low. Both lines responded with an increase in blood pressure after 6 weeks followed by a decrease to below baseline blood pressure at 12 weeks.This research was supported in part by an allocation from the General Research Fund of the University of Kansas.     

Ineffectiveness of carboxypeptidase B in inhibiting the pressor effect of incubated human plasma

Résumé L'action vasopressive chez le rat néphrectomisé, produite par l'injection du plasma humain lors de l'incubation à 38 C pendant plusieurs heures n'est pas due à la libération de plasmakinines. La carboxypeptidase B in vivo à des doses que produisent l'abolition des effets de la bradykinine et d'autres plasmakinines, ne modifient pas l'action vasopressive soit du plasma incubé soit de sa fraction active.     

Lack of effect of ciliarectomy on the fine structure of the small multiple endings in the extraocular muscles of the rat

Zusammenfassung Die motorischen Endplatten der nicht myelinhaltigen Nervenfasern in den Augenmuskeln der Ratte wurden elektronenmikroskopisch untersucht. Strukturelle Veränderungen treten nach Entfernen des Ganglion ciliare nicht auf.     

Massive striatal dopamine release in acute cerebral ischemia in rats

Summary Extracellular dopamine, 3,4-dihydroxyphenylacetic acid (DOPAC) and cerebral blood flow were simultaneously determined using in vivo brain dialysis and a hydrogen clearance method in the striatum of spontaneously hypertensive rats during ischemia and after recirculation. Massive striatal dopamine release was demonstrated in acutely induced ischemic brain.     

The dopaminergic innervation as observed by immunohistochemistry using anti-dopamine serum in the rat cerebral cortex

Summary By using an antiserum raised against dopamine bound to bovine serum albumin, thinner dopamine-labeled nerve terminals were visualized immunohistochemically within neocortical areas, in addition to well-documented dopaminergic innervation into the prefrontal and limbic cortices.This study was supported in part by a Grant-in-Aid for Scientific Research on Priority Areas, Japanese Ministry of Education, Science, Culture (No. 62623002).     

Accelerated synthesis of dopamine in the rat brain after methadone

Riassunto Nei ratti, ild, l-metadone fa aumentare significativamente i livelli di acido omovanillico e stimola il turnover della dopamina nei gangli della base. Il destro isomero è inattivo.     

Sympatho-inhibitory mechanisms acting at sympathetic ganglia to attenuate hypothalamic-induced pressor effect in the cat

Summary Pressor and tachycardic effects induced in the cat by stimulation of a lateral hypothalamic (LH) site, are shown to be mediated by sympathetic ganglia nicotinic receptor, and potentiated under atropine methyl nitrate sympathetic ganglia blockage. It is postulated that a sympatho-inhibitory pathway muscarinic ganglionic mechanism, co-activated by the LH stimulation, attenuates the pressor and tachycardic effects, the potentiation presumably being a manifestation of blockage of that mechanism.     

Sympatho-inhibitory mechanisms acting at sympathetic ganglia to attenuate hypothalamic-induced pressor effect in the cat

Pressor and tachycardic effects induced in the cat by stimulation of a lateral hypothalamic (LH) site, are shown to be mediated by sympathetic ganglia nicotinic receptor, and potentiated under atropine methyl nitrate sympathetic ganglia blockage. It is postulated that a sympatho-inhibitory pathway muscarinic ganglionic mechanism, co-activated by the LH stimulation, attenuates the pressor and tachycardic effects, the potentiation presumably being a manifestation of blockage of that mechanism.     

Blood pressure lowering effect of eicosapentaenoic acid-rich diet in normotensive,hypertensive and hyperlipemic subjects

Summary A mackerel diet or a herring diet in which two cans of fish fillet were consumed daily over 2 weeks within a prescribed regimen, in a crossover design, were given to 15 normotensive volunteers, 14 patients with mild essential hypertension and eight patients with type IV and V hyperlipoproteinemia (HLP). In normotensives a markedly lower systolic and diastolic blood pressure at the end of the period on the mackerel diet could be observed, whereas in hypertensive and hyperlipemic subjects only systolic blood pressure was significantly decreased. After the herring diet, which served as control, changes in blood pressure were of a minor degree.     

Suppression of natural killer cell activity in mouse spleen lymphocytes by several dopamine receptor antagonists

The effects of dopaminergic receptor inhibitors such as thiothixine (D₁/D₂), fluphenazine (D₁/D₂), trifluoperazine (D₁/D₂), pimozide (D₂), flupenthixol (D₁/D₂), (+/–)-SKF 83566 (D₁), and spiperone (D₂) on splenic natural killer (NK) cell cytotoxic activities were assessed in vitro using mouse spleen lymphocytes or enriched NK cells. Both the activities of the splenic NK cell cytotoxicity and the effector-target cell conjugation were suppressed by thiothixine, fluphenazine, and trifluoperazine at concentrations from 2.64 to 14.78 M. In addition, the augmentation of the cytolytic activity of NK cells induced by interferon- or interleukin-2 was antagonized by pretreatment with these neuroleptic compounds. However, neither the splenic NK cell cytotoxicity nor the effector-target cell conjugation were affected by treatment with other neuroleptic compounds such as pimozide, flupenthixol, (+/–)-SKF 83566, and spiperone. Thus, it appears that neuroleptic compounds such as thiothixine, fluphenazine, and trifluoperazine may act through the mechanisms other than a dopaminergic pathway to affect the NK cell-target cell interaction.     

The nature of posterior hypothalamic projections to cardiorespiratory centers in the brainstem

Summary Focal electrical stimulation of the midlateral posterior hypothalamus in the rat produces rapid shallow respiration accompanied by a rise in arterial blood pressure. Stimulation of presumably intrinsic neurons only by glutamate induces slower deeper respiration associated with a fall in blood pressure.