Nitric oxide metabolites in the cisternal cerebral spinal fluid of patients with subarachnoid hemorrhage

OBJECTIVE

To investigate nitric oxide (NO) metabolism after subarachnoid hemorrhage (SAH).

METHODS

We measured the concentrations of the NO metabolites, nitrite and nitrate, in cerebrospinal fluid (CSF) obtained from the cisternal drainage of patients with SAH. Studies were performed for 31 patients who had undergone surgical obliteration of bleeding aneurysms within 3 days of their hemorrhage. The concentrations of nitrite and nitrate in the CSF were measured for 14 days using a nitrate/nitrite kit and samples that were obtained on a daily basis from the cisternal drainage.

RESULTS

Compared with the control values in the CSF (2.6 +/- 0.4 mumol/L, n = 14) obtained from patients with hemifacial spasm, trigeminal neuralgia, or nonruptured aneurysms, the concentrations of nitrite and nitrate in the CSF were significantly elevated in the acute stage of SAH and remained elevated. The concentration of NO metabolites may correlate with the amount of bleeding, inasmuch as the values in patients in Fisher Group 3 (n = 25) were higher than those in patients in Fisher Group 2 (n = 6). The concentration of nitrate was higher than that of nitrite, suggesting that NO in the subarachnoid space is mainly absorbed by hemoglobin and degraded to nitrate. No differences were demonstrated in patients treated with high doses of methylprednisolone (n = 17) compared with those treated with usual-dose steroids (n = 14). Steroids are known to prevent the formation of inducible NO synthase mediated by inflammatory cytokines.

CONCLUSION

NO metabolism in the brain is stimulated after SAH. Nitrate is the dominant NO metabolite in CSF after SAH. The involvement of inducible NO synthase in the pathophysiology of NO metabolism after SAH was not clearly suggested based on the present data.

Ketotifen prevents gastric hyperemia induced by intracisternal thyrotropin-releasing hormone at a low dose

The thyrotropin-releasing hormone (TRH) analog, RX 77368, (p-Glu-His-(3,3'-dimethyl)-Pro-NH2) injected intracisternally (i.c.) at low doses increases gastric mucosal blood flow through vagal cholinergic and calcitonin gene-related peptide dependent pathways. The influence of the mast cell stabilizer, ketotifen, on i.c. injection of RX 77368 (1.5 ng)-induced changes in gastric mucosal blood flow (hydrogen gas-clearance technique), gastric acid secretion and mean arterial pressure was studied in urethane-anesthetized rats. RX 77368 increased gastric blood flow by 131% and systemic arterial pressure by 11 mm Hg and decreased gastric mucosal vascular resistance by 54% whereas acid secretion was not altered within the 30 min period post injection. Ketotifen had no effect on these basal parameters but abolished i.c. RX 77368-induced increased gastric mucosal blood flow and decreased gastric vascular resistance. These data suggest that mast cells may be part of the peripheral mechanisms involved in vagal gastric hyperemia induced by TRH analog injected i.c. at a low dose.

Inhibition of cerebral metabolic and circulatory responses to nitrous oxide by 6-hydroxydopamine in dogs

PURPOSE

To determine whether cerebral metabolic and circulatory consequences of N2O result from activation of the sympathoadrenal system. The effects of pretreatment with intracisternal injection of 6-OHDA, which produces chemical sympathectomy, were studied in dogs.

METHOD

Seven days before measurement dogs were pretreated with intracisternal injection of either saline vehicle (sham-group) or 100 micrograms.kg-1 6-hydroxydopamine (6-OHDA, group). Cerebral blood flow (CBF) was measured using an electromagnetic flow-meter probe and cerebral metabolic rate for oxygen (CMRO2) was calculated as the product of CBF and arterial-sagittal sinus blood oxygen content difference [C(a-v)O2].

RESULTS

In the sham group, N2O (60%) increased CMRO2 from 6.11 +/- 0.21 ml.100 g-1.min-1 to 7.10 +/- 0.39 ml.100 g-1.min-1 and CBF from 63 +/- 5 ml.100 g-1.min-1 to 173 +/- 26 ml.100 g-1.min-1. In the 6-OHDA group, CMRO2, did not change during N2O exposure, whereas CBF increased from 61 +/- 3 ml.100 g-1.min-1 to 135 +/- 19 ml.100 g-1.min-1 but less then in the sham group. The 6-OHDA group displayed a reduction in cortical noradrenaline (NA) concentration from 263.2 +/- 35.6 ng.g-1 to 102.7 +/- 16.5 ng.g-1. Cortical dopamine (DA) concentration was not affected by 6-OHDA administration.

CONCLUSION

These results suggest that most of the increase in CMRO2 and at least a part of the increase in CBF during N2O exposure in the sham-group are related to sympathoadrenal-stimulating effects of N2O.

Pretreatment with the dopamine agonist quinpirole inhibits central antihypertensive mechanisms in rats

1. Intravenous or central treatment of spontaneously hypertensive rats (SHR) with the dopamine D2 receptor agonist quinpirole caused a short-lasting pressor response with little effect on heart rate. 2. At 30 min after intravenous administration of quinpirole, the antihypertensive effect of rilmenidine was significantly inhibited. This interaction of quinpirole and rilmenidine was similarly observed when quinpirole was administered either intravenously (0.3 or 0.1 mg/kg), in the lateral cerebral ventricles (0.1 mg/kg) or intracisternally (0.1 mg/kg) or when rilmenidine was administered intravenously (1 mg/kg) or intracisternally (0.1 mg/kg). 3. The apparent desensitization to the antihypertensive effect of rilmenidine 30 min after pretreatment with quinpirole was not observed after a 4 or 24 h interval. 4. These data suggest that quinpirole has prolonged effects on central sympathetic vasomotor mechanisms that are the target of centrally acting antihypertensive drugs. These and previous results show a functional interaction between central dopamine D2 receptor activation and sympathetic responses mediated by a wide range of different receptors, including imidazoline and 5-hydroxytryptamine 5-HT1A-receptors and alpha 2-adrenoceptors.

Naltrindole, a selective delta-opioid receptor antagonist, potentiates the lethal effects of cocaine by a central mechanism of action

The potentiation of the toxic and lethal effects of cocaine by the selective delta-opioid receptor antagonist naltrindole was explored in unrestrained, unanesthetized rats that received a continuous intravenous infusion of cocaine until death. The lethal dose of cocaine was lowered dose dependently in animals administered naltrindole intracisternally (3.0-30 microg), but not intravenously (30-300 microg). There was also a decrease in the lethal dose of cocaine following an injection of the nonselective opioid antagonist naltrexone, but not naloxone. However, the seizure-producing dose of cocaine was decreased dose dependently in rats that received naltrindole, regardless of the route of administration, naloxone, or naltrexone. In contrast, the effect of cocaine on heart rate was altered only by centrally administered naltrindole or intravenous naltrexone, with a dose of 30 microg naltrindole and 10 mg/kg naltrexone abolishing the bradycardic effect of cocaine. Despite this, neither naltrindole nor naltrexone changed the hypertensive effect of cocaine. Higher doses of naltrindole (100 microg i.c.) produced significant increases in heart rate and mean arterial pressure and were not tested in combination with cocaine. Because the lethal dose of cocaine was reduced only when naltrindole was administered intracisternally, the potentiation of the lethal effects of cocaine by naltrindole is through a central mechanism of action that may involve changes in cardiovascular function.

Acidic amino acid accumulation by rat choroid plexus during development

Acidic amino acid accumulation by the choroid plexuses of the lateral ventricles was investigated using 1, 2, 3 week and adult (7-10 weeks old) rats. The accumulation from both blood and CSF sides of the choroid plexuses were investigated. The uptake from blood side was studied using the bilateral in situ brain perfusion, and time-dependent uptake profiles (2, 10, 20, and 30 min) of 14C-labelled aspartate, glutamate, and NMDA were measured. [3H]Mannitol was also included in perfusion fluid as a baseline for [14C]amino acid uptake into choroidal tissue. Uptake of [14C]aspartate and [14C]glutamate declined with age, while [14C]NMDA showed no significant uptake at any age. Twenty min [3H]mannitol uptake in the 1-week-old rat was significantly greater than the adult (P < 0.05). The K(m) for [14C]aspartate and [14C]glutamate obtained from multiple time uptake profiles also showed reduction with development but it was greater than that for mannitol. [14C]Aspartate declined from 69.8 +/- 21.1 microliters.min-1.g-1 in the neonate to 40.6 +/- 4.0 microliters.min-1.g-1 in the adult (P < 0.05), while glutamate showed a sharper decline from 78.9 +/- 24.2 microliters.min-1.g-1 to 17.7 +/- 5.4 microliters.min-1.g-1 (P < 0.01). Accumulation of 14C-labelled aspartate and glutamate by the choroid plexus from CSF side was also measured using ventriculo-cisternal perfusion. The accumulation in the adult was found to be 2-3 times greater than that in the neonatal rat (P < 0.05) for both amino acids. The uptake from either side was found to be saturable, stereospecific, not inhibited by neutral amino acid analogues, and shared by both aspartate and glutamate.

Antagonism of morphine-like discriminative effects by beta-funaltrexamine

beta-Funaltrexamine (beta-FNA), an irreversible antagonist at the mu-opioid receptor, was administered intracisternally to rats discriminating between subcutaneous injections of saline and 3.0 mg/kg of morphine in order to reduce the size of the receptor reserve. beta-FNA alone (10 micrograms) occasioned substantial morphine-appropriate responding for at least 6 h but mainly saline-appropriate responding 24 h after administration, the pretreatment interval for most experiments. beta-FNA (3.0-30 micrograms) dose-dependently shifted to the right stimulus-generalization curves for morphine and fentanyl; 10 micrograms also shifted to the right the curves for meperidine and buprenorphine. In all cases, antagonism was fully surmounted by higher doses of the agonist, even after inactivation of more than 75% of mu-opioid receptors. This antagonist effect of beta-FNA is smaller than that reported previously in tests of analgesia, suggesting that the receptor reserve for the discriminative effects of morphine-like drugs is larger than the receptor reserve for their analgesic effects. beta-FNA produced larger rightward displacements of the morphine and buprenorphine curves than of the fentanyl curve and inactivated a larger fraction of the receptors acted upon by those drugs compared to fentanyl. Results with meperidine were intermediate. This suggests that the receptor population mediating morphine-like discriminative effects of fentanyl is not identical to the receptor population mediating these effects of morphine and buprenorphine.

Novel methods for adenovirus-mediated gene transfer to blood vessels in vivo

Adenovirus-mediated gene transfer is a promising method for studies of vascular biology and potentially for gene therapy. Intravascular approaches for gene transfer to blood vessels in vivo generally require interruption of blood flow and have several limitations. We have used two alternative approaches for gene transfer to blood vessels in vivo using perivascular application of vectors. First, replication-deficient adenovirus expressing nuclear-targeted bacterial beta-galactosidase was injected into cerebrospinal fluid via the cisterna magna of rats. Leptomeningeal cells over the major arteries were efficiently transfected, and adventitial cells of large vessels and smooth muscle cells of small vessels were occasionally stained. When viral suspension was injected with the rat in a lateral position, the reporter gene was expressed extensively on the ipsilateral surface of the brain. Thus, adenovirus injected into cerebrospinal fluid provides gene transfer in vivo to cerebral blood vessels and, with greater efficiency, to perivascular tissue. Furthermore, positioning of the head may 'target' specific regions of the brain. Second, vascular gene delivery was accomplished by perivascular injection of virus in peripheral vessels. Injection of the adenoviral vector within the periarterial sheath of monkeys resulted in gene transfer to the vessel wall that was substantial in magnitude although limited to cells in the adventitia. Approximately 20% of adventitial cells expressed the transgene, with no gene transfer to cells in the intima or media. These approaches may provide alternative approaches for gene transfer to blood vessels, and may be useful for studies of vascular biology and perhaps vascular gene therapy.

The blood supply of the hypoglossal nerve: the microsurgical anatomy of its cisternal segment

BACKGROUND

While the characteristics of the vasculature of the second (intracanalicular) segment of the hypoglossal nerve are well known, the vascularization of the first (cisternal) segment of this nerve has not been examined so far. Many pathologic processes and malformations can be located in the premedullary cistern, which may affect the vasculature of the cisternal segment. Consequently, we decided to examine the blood supply of the cisternal segment.

METHODS

The anatomic features of the cisternal segment and its vasculature were examined in 15 hypoglossal nerves after injection of india ink and gelatin into the vertebrobasilar arterial system.

RESULTS

The cisternal segment was noted to consist of 3-15 long roots, which usually formed two trunks of the hypoglossal nerve. The roots of each nerve received blood from the anterolateral and the lateral medullary arteries, which ranged from 3 to 5 in number and between 100 microns and 500 microns in caliber. These arteries may arise from the perforating branches or the pontomedullary branch of the basilar artery; the vertebral artery or its perforators; the anterior spinal artery or its vascular roots; the posterior spinal artery; and the posterior inferior cerebellar artery. The main hypoglossal arteries, which ranged in diameter from 20 microns to 80 microns, always coursed along the dorsal surface of the roots of the hypoglossal nerve.

CONCLUSIONS

The cisternal segment of the hypoglossal nerve was always vascularized by several vessels, which mainly originated from the vertebral artery and its branches. This observation was discussed from the neurosurgical point of view.

Intracisternal injection of opioids induces itch-associated response through mu-opioid receptors in mice

We examined whether opioids, especially morphine, would centrally elicit scratching in mice and determined some characteristics of the scratch-inducing action of opioids. When intracisternally (i.c.) injected, morphine (0.1-3 nmol/mouse) produced a dose-dependent increase in scratching of the face, but not of the ears, head and body trunk. When injected intradermally into the rostral part of the back, morphine (at most potent i.c. dose of 3 nmol/mouse or higher) did not increase the scratching of the injected site. Facial scratching of the mouse induced by i.c. injection of morphine (0.3 nmol/mouse) was almost abolished by distraction and by naloxone (1 mg/kg, s.c.). [D-Ala2, N-Me-Phe4, Gly5-ol]Enkephalin (DAMGO) (0.03-2 nmol), but not [D-Pen2,5]enkephalin (DPDPE) and U-50,488, dose-dependently elicited facial scratching by i.c. injection. These results suggest that morphine and DAMGO increased facial scratching, probably mediated by central opioid mu-receptors in mice, and such scratching was due to a sensation, probably itching. The present animal model may be useful for analyzing opioid-mediated central itching.

Evidence for a dual mechanism of gastric motor responses to intravenously administered endothelin-1 in anesthetized rats

We have recently reported that endothelin-1 (ET-1), administered intracisternally or microinjected into the DVC of rats, increases gastric motor function via vagal pathways. To determine whether circulating ET-1 acts peripherally or centrally to alter gastric motility, ET-1 (30 and 300 pmol/kg) was administered intravenously in alpha-chloralose anesthetized rats, while monitoring intragastric pressure, gastric motility, heart rate and blood pressure. Endothelin-1, at a dose of 300 pmol/kg, increased intragastric pressure, stimulated pyloric circular muscle contractile activity, and increased arterial pressure. When ET-1 (300 pmol/kg) was administered after bilateral vagotomy at midcervical level, a marked gastric motor inhibition with an increase in arterial blood pressure were observed. We conclude that the gastric motor effects of circulating ET-1 are a result of central excitatory and peripheral inhibitory actions of the peptide.

Intracisternal injection of basic fibroblast growth factor reduces the severity of gastric mucosal lesions evoked by ethanol in rats

This study was conducted to examine the hypothesis that basic fibroblast growth factor (bFGF) may have an anti-ulcer action through an acid-independent mechanism. The intracisternal injection of bFGF (1 microgram/10 microliters) significantly attenuated the development of gastric mucosal damage evoked by either subcutaneous indomethacin or intragastric absolute ethanol. On the other hand, intraperitoneally injected bFGF (1 microgram) failed to inhibit the formation of gastric mucosal injury by indomethacin or ethanol. These results suggest that bFGF acts in the brain to exert a gastroprotective action. Since ethanol-induced gastric lesion formation does not depend upon luminal acid, we speculate that an acid-independent mechanism may mediate the anti-ulcer action of central bFGF.

Trigeminovascular stimulation in conscious rats

Intracisternal infusion of capsaicin was used to induce intracranial trigeminovascular stimulation in conscious rats. Both behaviour and trigeminal nucleus caudalis c-fos expression were examined. Exploratory behaviour was dose-dependently reduced and different types of behaviours were induced with various doses of capsaicin. Head grooming and scratching show that intracranial activation of trigeminal afferents can be referred as extracranial trigeminal stimulation. Analysis of behaviour exhibited during trigeminovascular stimulation may provide a powerful tool to study effects of central acting anti-migraine drugs.

Structural scoliosis model in dogs with experimentally induced syringomyelia

STUDY DESIGN

Animal scoliosis model associated with syringomyelia.

OBJECTIVE

To investigate the pathogenesis of scoliosis produced in dogs with kaolin-induced syringomyelia.

SUMMARY OF BACKGROUND DATA

Kaolin injected into the cisterna magna produces basilar arachnoiditis, leading to hydrocephalus and syringomyelia. There have been no reports on scoliosis associated with kaolin-induced syringomyelia.

METHODS

Kaolin was injected percutaneously into the cisterna magna of 11 beagles 6-8 weeks after birth. Roentgenograms, computed tomography, and magnetic resonance imaging were obtained. The spinal cord and the paraspinal muscles were examined histologically. Structural changes of the vertebral column were analyzed with calcein and tetracycline labeling.

RESULTS

Hydrocephalus occurred in nine dogs. A communicating syringomyelia appeared in five dogs. Mild scoliosis developed in two dogs, and severe cervical scoliosis in one dog. In the syringomyelia cases, acute or subacute inflammatory changes were found in the spinal cord. Damage of the anterior and posterior horn cells was more marked in the scoliotic animals than in the nonscoliotic animals. In three of the syringomyelia cases, including two scoliosis cases, the paraspinal muscles revealed neurogenic changes. The deformed vertebrae appeared to diminish rather than to increase the deformity in severe scoliosis.

CONCLUSION

The exact mechanism of the development of scoliosis could not be identified, although an etiologic relation with malfunction of the central nervous system was noted. This model may be useful to study scoliosis experimentally.

Once-daily gentamicin therapy for experimental Escherichia coli meningitis

In vitro and in vivo studies have demonstrated that the bacteriologic efficacy of once-daily aminoglycoside therapy is equivalent to that achieved with conventional multiple daily dosing. The impact of once-daily dosing for meningitis has not been studied. Using the well-characterized rabbit meningitis model, we compared two regimens of the same daily dosage of gentamicin given either once or in three divided doses for 24 or 72 h. The initial 1 h mean cerebrospinal fluid (CSF) gentamicin concentration for animals receiving a single dose (2.9 +/- 1.7 micrograms/ml) was threefold higher than that for the animals receiving multiple doses. The rate of bacterial killing in the first 8 h of treatment was significantly greater for the animals with higher concentrations in their CSF (-0.21 +/- 0.19 versus -0.03 +/- 0.22 log10 CFU/ml/h), suggesting concentration-dependent killing. By 24h, the mean reduction in bacterial titers was similar for the two regimens. In animals treated for 72 h, no differences in bactericidal activity was noted for 24, 48, or 72 h. Gentamicin at two different dosages was administered intracisternally to a separate set of animals to achieve considerably higher CSF gentamicin concentrations. In these animals, the rate of bacterial clearance in the first 8 h (0.52 +/- 0.15 and 0.58 +/- 0.15 log10 CFU/ml/h for the lower and higher dosages, respectively) was significantly greater than that in animals treated intravenously. In conclusion, there is evidence of concentration-dependent killing with gentamicin early in treatment for experimental E. coli meningitis, and once-daily dosing therapy appears to be at least as effective as multiple-dose therapy in reducing bacterial counts in CSF.

Intracisternal TRH and RX 77368 potently activate gastric vagal efferent discharge in rats

The influence of intracisternal (ic) TRH and the stable TRH analog, RX 77368, on gastric vagal efferent discharge (GVED) was investigated in urethane-anesthetized rats. Consecutive IC injections of TRH (3, 30, and 300 ng) at 60 min intervals stimulated dose dependently multi-unit GVED with a peak increase of 90 +/- 21%, 127 +/- 18% and 145 +/- 16% respectively. In two separate studies, IC injection of RX 77368 at 1.5 or 15 ng stimulated multi-unit GVED by 142 +/- 24% and 244 +/- 95% respectively. Saline injection IC had no effect on GVED. RX 77368 (1.5 ng, ic) action was long lasting (84 +/- 13 min) compared with TRH (3 ng: 44 +/- 7 min). Single-unit analysis also showed that 13 of 13 units responded to ic RX 77368 (1.5 ng) by an increase in activity. These data indicate that low doses of TRH injected ic stimulate vagal efferent outflow to the rat stomach and that RX 77368 action is more potent than TRH.

Influence of [4Cl-D-Phe6,Leu17]VIP on VIP- and central TRH-induced gastric hyperemia

The specific VIP receptor antagonist, [4Cl-D-Phe6,Leu17]VIP, infused i.v. blocked close-intra-arterial infusion of VIP-induced increase in gastric mucosal blood flow (GMBF, measured by the hydrogen gas clearance), and decrease in mean arterial blood pressure while not influencing basal levels in urethane-anesthetized rats. The thyrotropin-releasing hormone (TRH) stable analog, RX 77368, injected intracisternally (IC, 30 ng) increased GMBF and blood pressure. The VIP antagonist did not significantly reduce the GMBF response to IC RX 77368 while enhancing the rise in blood pressure. These findings indicate that [4Cl-D-Phe6,Leu17]VIP is an antagonist for exogenous VIP-induced gastric hyperemia and hypotension and that VIP modulates the systemic blood pressure response to IC RX 77368 at 30 ng while not playing a primary role in the increase of GMBF.

Functional changes induced by neonatal cerebral 6-hydroxydopamine treatment: effects of dose levels on behavioral parameters

Male Sprague-Dawley rats were treated neonatally with either of three different doses of 6-hydroxydopamine (6-OHDA): 50 micrograms i.c., 75 micrograms i.c., or 2 x 100 micrograms i.c.v., 30 min after a subcutaneous injection of desipramine (DMI, 25 mg/kg), in order to obtain selective lesions of mesencephalic dopamine (DA) neurons to different extents. From juvenile ages onwards, rats in each dose condition were tested for spontaneous motor activity and exploration in an openfield/holeboard setting measuring ambulation, rearing and head-dips. Between 77 and 78 days, the animals were tested in a modified, enclosed radial arm maze, followed 1 week later by tests in the circular swim maze. Finally, motor activity was tested in automated activity test chambers. In the openfield/holeboard setting, hyperactivity was seen for both rearing and ambulation in rats administered 50 micrograms 6-OHDA, whereas the 75 micrograms and 2 x 100 micrograms groups showed hyperactivity for ambulation, but hypoactivity for rearing and head-dips. All three dose groups demonstrated a retardation of learning in the radial arm maze. The 75 and 2 x 100 micrograms groups, but not the 50 micrograms group, showed impairments of acquisition in the swim maze. In the activity test chambers locomotion and rearing behavior varied as a function of 6-OHDA dose, being negatively and positively, respectively, related to DA concentration in striatum. These results show that the extent of the neonatal DA lesion determines both changes in motor- and exploratory activity as well as the occurrence and severity of acquisition impairment in spatial learning tasks.

Experimental intracerebral hemorrhage: description of a double injection model in rats

For experimental purposes, the most common technique of producing an intracerebral hematoma in rats is the injection of unclotted autologous blood. All modifications of this model share the problem that size and extension of the hematoma are not reproducible, because the injected blood either ruptures into the ventricular system or it extends to the subarachnoid or subdural space. Therefore a double injection model of experimental intracerebral hemorrhage in rats has been developed using 19 male Sprague-Dawley rats. After inducing anesthesia a cannula was stereotactically placed into the caudate nucleus and an intracerebral hematoma was produced with the double injection method in which first a small amount of fresh autologous blood is injected which is allowed to clot (preclotting) in order to block the way back along the needle track; the actual hematoma is produced in a second step of the injection. The clot volume was measured on stained serial sections. A total injection volume of 50 microliters of autologous blood produced intracerebral hematomas of 41.1 +/- 10.0 microliters and of similar shapes. The double injection method allows to generate reproducible hematomas in rats. This new model of intracerebral hemorrhage will allow further investigation of fibrinolytic and cytoprotective therapies.

Indications for cisternal irrigation with urokinase in postoperative patients with aneurysmal subarachnoid haemorrhage

The use of cisternal drainage can lead to complications such as shunt-dependent hydrocephalus and meningitis. We assessed the indications for cisternal irrigation with urokinase in postoperative patients with aneurysmal subarachnoid haemorrhage (SAH). The SAH scores by CT on admission and on the day after surgery were used to evaluate two parameters: the total amount of subarachnoid blood on admission and the clearance rate of subarachnoid blood by surgery. In patients whose parameters values belonged to the range where the total SAH score on admission exceeded 10 points and the surgical clearance rate was less than 50%, the possibility of cerebral infarction was significantly higher in patients without than in those with irrigation (p < 0.05). However, there was no difference between patients with and without irrigation for parameter values outside of the range. Therefore, this range may be useful in providing stricter indications for irrigation therapy with urokinase and thus avoiding the complications of cisternal drainage.

Development of calcitonin gene-related peptide slow-release tablet implanted in CSF space for prevention of cerebral vasospasm after experimental subarachnoid haemorrhage

The calcitonin gene-related peptide (CGRP), a known potent intrinsic cerebral vasodilator, is contained in the sensory nerves from trigeminal ganglia that inervate the cerebral arteries. We previously reported that human alpha CGRP (hCGRP) dilates spastic cerebral arteries after experimental subarachnoid haemorrhage (SAH) in rabbits. In the present study, we investigated the prophylactic potential of a sustained higher cerebrospinal fluid level of hCGRP against experimental cerebral vasospasm. An hCGRP slow-release tablet (hCGRP s-r tablet) was developed for cisternal implantation. Experimental SAH was induced by percutaneous cisternal injection of autologous arterial blood. Angiography was initiated on day 1 (before SAH) and performed everyday. The hCGRP s-r tablet was implanted into the cisterna magna on day 2 in the treated groups. The spastic response of the basilar artery was maximized on day 4 in the non-treated (80.7% of day 1) and the placebo-treated (79.3%) groups. In contrast, the arterial diameters on day 4 were 96.1% and 90.5% of day 1 in the groups implanted with hCGRP 24 micrograms and 153 micrograms s-r tablets, respectively. We also measured the concentration of hCGRP in the cerebrospinal fluid (CSF) following implantation of the hCGRP 24 micrograms s-r tablet in the cisterna magna. The hCGRP concentration before implantation was below the dectable level. Following implantation, the hCGRP level in the CSF was 23.12 nmol/L on the second day and remained at elevated levels until the fifth day. These experiments suggest that the intrathecal single implantation of the hCGRP s-r tablet could produce an elevated concentration of hCGRP in the CSF over five days and have prevented the cerebral vasospasm after SAH in the rabbit. The hCGRP s-r tablet may be clinically applicable in the treatment of patients with SAH against cerebral vasospasm.

Trigeminal afferents and brainstem centers involved in the occurrence of cerebral vasospasm

Cisternal injections of blood in the rat and squirrel monkey produce an angiographically demonstrable biphasic vasospasm with a maximal late spasm at two days in the rat and six days post-subarachnoid hemorrhage (SAH) in the monkey. The SAH induces a decrease in cerebral blood flow of about 25% and a corresponding increase in glucose uptake of between 30% and 50%. In about half of the animals low-flow areas were noted in the cortex and the basal ganglia with a corresponding marked increase in glucose uptake. Lesioning of the A2-nucleus, its ascending pathway or the median eminence prevents the occurrence of spasm. Similarly, treatment with a substance P antagonist or gammaglobulin against substance P prevents or significantly reduces the degree of spasm. A unilateral post-ganglionic trigeminal lesion causes an ipsilateral constriction of the cerebral arteries of 27%, while a preganglionic lesion does not affect the baseline diameter. A pre- or post-ganglionic trigeminal lesion induces an increase in glucose uptake globally of about 50% without influencing cerebral blood flow. Following SAH the decrease in blood flow in both groups of lesioned animals is similar to that seen in controls. After SAH there is no further change in glucose uptake in the animals with a preganglionic lesion, while in the post-ganglionically lesioned animals there is an additional increase in glucose uptake of about 50% as compared to controls or the animals with a preganglionic lesion.

Intracisternally applied angiotensin II does not excite reticulospinal vasomotor neurons in anesthetized rats

We examined whether vasomotor neurons in the rostroventrolateral reticular nucleus of the medulla oblongata might be responsible for an acute increase in arterial pressure, elicited by application of angiotensin II in the central nervous system, as suggested by others. In urethane-pentobarbital-anesthetized and ventilated rats, intracisternal administration of angiotensin II (1-30 nmol, infused over a period of 30 s) produced a dose-dependent pressor response, which was abolished by intracisternal application of [Sar1, Thr8]angiotensin II (100 nmol), an angiotensin II receptor antagonist. The pressor response, however, was neither preceded by nor associated with increased discharges of vasomotor neurons with slow- and fast-conduction axons in the rostroventrolateral reticular nucleus and of lumbar sympathetic chain and renal sympathetic nerves. Intravenous injections of [beta-mercapto-beta, beta-cyclopentamethylenepropinyl1,-O-Et-Tyr2, Val4, Arg8]vasopressin, a vasopressin receptor antagonist, largely abolished the central angiotensin II-induced pressor response, while a blockade of ganglionic transmission with hexamethonium and disruption of descending sympathoexcitatory output were ineffective. We conclude that central administration of angiotensin II, under the experimental conditions and at the doses, evokes an acute pressor response largely through the release of vasopressin, not by exciting vasomotor and sympathetic neurons.

Inhibition of nitric oxide synthase attenuates blood-brain barrier disruption during experimental meningitis

Increased permeability of the blood-brain (B-B) barrier is observed during meningitis. Preventing B-B barrier alterations is important because adverse neurological outcomes are correlated with breeches in barrier integrity. It was hypothesized that pathological production of nitric oxide (NO) contributes to B-B barrier disruption during meningitis in the rat. Experimental meningitis was induced by intracisternal (i.c.) administration of lipopolysaccharides (LPS) or vehicle. Groups of rats were concomitantly infused intravenously (i.v.) with saline or the NO synthase inhibitor, aminoguanidine (AG). Eight h after i.c. dosing, B-B barrier alterations were quantitated pharmacokinetically using [14C]sucrose. Serum and regional brain tissues were obtained 0-30 min after tracer dosing and sucrose influx transfer coefficients (Kin(app)) were calculated from the brain tissue data. Compared to the control groups (i.c. vehicle/i.v. saline), the Kin(app) of the i.c. LPS/i.v. saline group increased 1.6-2.1-fold in various brain regions, thus confirming previous observations of increased [14C]sucrose barrier penetration during meningeal inflammation. Remarkably, i.v. administration of AG to i.c. LPS-treated rats significantly inhibited meningeal NO synthesis and decreased Kin (app) permeability alterations in the B-B barrier, compared to i.c. LPS/i.v. saline-treated rats. Regional brain Kin (app) estimates in the i.c. LPS/i.v. AG group were similar to control groups (i.c. vehicle/i.v. AG and i.c. vehicle/i.v. saline). In conclusion, these data suggest the general concept that excessive NO production during neuroinflammatory diseases contributes to disruption of the blood-brain barrier.

Neuronal pathways involved in abdominal surgery-induced gastric ileus in rats

The 20-min rate of gastric emptying of a noncaloric solution and c-fos expression detected by immunohistochemistry in the brain were monitored 3 h after abdominal surgery performed under 10-min enflurane anesthesia in rats. Abdominal surgery (laparotomy and 1-min manipulation of the cecum) decreased gastric emptying from 60.8 +/- 3.4 to 25.9 +/- 3.4%. Capsaicin applied to the celiac/superior mesenteric ganglia 2 wk before the experiment reduced the delay in gastric emptying induced by abdominal surgery (46.3 +/- 3.4%), whereas perivagal capsaicin application had no effect (23.6 +/- 7.9%). The corticotropin-releasing factor (CRF) antagonist [D-Phe12, Nle21,38,C alpha MeLeu37]CRF-(12--41) injected intracisternally (10-20 micrograms) prevented postoperative gastroparesis induced by surgery, while having no effect on basal gastric emptying. Abdominal surgery increased the number of Fos-positive cells in brain nuclei regulating autonomic outflow: the nucleus of the solitary tract, locus ceruleus, paraventricular nucleus, and supraoptic nucleus of the hypothalamus. These data indicate that capsaicin-sensitive splanchnic afferent fibers and activation of CRF receptors in the brain are part of the neuronal circuitry mediating gastric stasis 3 h after abdominal surgery.

Innovations in aneurysmal subarachnoid hemorrhage: intracisternal t-PA for the prevention of vasospasm

Aneurysmal subarachnoid hemorrhage (SAH) affects approximately 30,000 people each year in North America. At least 30% of these patients will develop vasospasm as a result of the initial hemorrhage, and two thirds of these develop permanent disabilities or die. Blood deposited into the basal cisterns from the ruptured aneurysm can form thick clots around the major cerebral vessels. The by-products of the hemolyzed clots are believed to be responsible for the subsequent development of vasospasm. Hypervolemic, hypertensive, hemodilution therapy (HHHT) and nimodipine may improve outcome in some cases but there is no therapy known to prevent vasospasm in all patients. One potential therapeutic agent under investigation is tissue plasminogen activator (t-PA), a fibrinolytic enzyme. Instilled into the basal cisterns at time of aneurysm clipping, t-PA dissolves the clot so spasmogenic substances may be removed, thus preventing or reducing the severity of vasospasm.

Lipopolysaccharide and IL-1 alpha activate CNS pathways as measured by NK cell activity

The effect of lipopolysaccharide (LPS) on murine unstimulated and prestimulated natural killer (NK) cells and its ability to serve as an unconditioned stimulus was investigated. LPS injection induced a statistically significant increase in NK cell activity when compared with saline-treated control groups. To demonstrate the existence of communication between the peripheral immune system and the central nervous system (CNS), we used a single-trial conditioning paradigm in which camphor served as the conditioned stimulus (CS) and LPS as the unconditioned stimulus (US). Once a CS/US association is made, exposure of animals to the CS alone results in the conditioned response (i.e., increase in NK cell activity). Using 50 micrograms of LPS as the US produced a low but significant increase in NK cell activity when compared to control groups. However, 10 micrograms of LPS did not show a significant increase in NK cell activity. We also observed that interleukin-1 alpha (IL-1 alpha) injected intracisternally can serve as a US to condition a central neuroendocrine pathway. Because the dose of IL-1 alpha employed was too small to raise NK cell activity in the spleen, the NK cells themselves were formally not subjected to conditioning. These observations suggest that LPS and IL-1 alpha conditions the brain and that NK cell activity can be used as an indicator system to detect neuroendocrine signals arising from the activated pathway(s).

Herpes vector-mediated delivery of marker genes to disseminated central nervous system tumors

The present study investigated the ability of a recombinant herpes simplex virus type 1 (HSV) vector to deliver genes into disseminated brain tumor foci through intrathecal injection of the vector. The animal model was designed to simulate brain tumors with cerebrospinal fluid (CSF) metastases, which are found especially in the pediatric population. 9L gliosarcoma cells were injected both into the right frontal lobe and in through the cisterna magna of adult rats. The HSV vector, hrR3, was inoculated intrathecally 5 days later. This vector is defective in the gene for ribonucleotide reductase, and, therefore, replicates preferentially in dividing cells; it retains an intact HSV-thymidine kinase gene (HSV-tk). Two days after injection of the vector, immunohistochemical staining for HSV thymidine kinase (HSV-TK) revealed expression in frontal tumors, as well as in leptomeningeal tumor foci along the entire neuroaxis. HSV-TK-immunopositive cells were most frequent in small tumors contacting the CSF pathways. Frontal lobe tumors showed the highest density of HSV-TK-immunopositive cells around their periphery with little expression in central parts. Some paraventricular neurons temporarily showed HSV-TK-immunolabeling at this early time point. The number of HSV-TK-immunopositive tumor cells markedly decreased 5 days after injection of the HSV vector. In all animals, some toxicity was observed in the first 2-4 days after virus injection with extensive leptomeningeal inflammation. In conclusion, intrathecal application of HSV vectors can mediate widespread transfer of the therapeutic HSV-tk gene into disseminated tumors throughout the brain and CSF pathways. Although there was marked toxicity associated with intrathecal injection of this vector, this mode of gene delivery offers a promising approach for treatment of CSF-metastases in conjunction with development of less toxic vectors.

Continuous intracisternal and high cervical intrathecal bupivacaine analgesia in refractory head and neck pain

BACKGROUND

The upper cervical component of the spinomesencephalic tract and cranial nerves V, VII (nervus intermedius), IX, and X are involved in mechanisms of acute and chronic pain from head and neck structures. To date there is no reliable method for relief of refractory pain (i.e., pain that cannot be relieved by conventional pharmacologic therapies) from these structures. Therefore, we explored continuous intracisternal infusion of bupivacaine for the treatment of refractory pain of the head and neck.

METHODS

Intracisternal catheters were inserted in 13 adults with refractory nonmalignant (n = 4) and malignant (n = 9) pain from the head, face, mouth, neck, and upper extremities; 0.5% plain bupivacaine was infused continuously at rates of 1-7 (median 1.5) mg/h with optional bolus doses of 0.5-2.0 mg 4-2 times/h. The efficacy was assessed from pain relief (daily VAS(max), VAS(min), and VAS(mean) scores 0-10), daily doses of intracisternal bupivacaine and total opioid (expressed as mg parenteral morphine-eq), amount of nocturnal sleep, and rates of adverse effects.

RESULTS

The 13 patients were treated for 3-182 days (median 37, total 712 days), 3 patients being treated at home for 10-112 days (median 88, total 210 days). In one patient, the efficacy of the treatment could not be estimated because of advanced senility. Eleven of the remaining 12 patients obtained acceptable pain relief with daily doses of intracisternal bupivacaine ranging from 20 to 118 mg (median 37 mg): VAS(mean) scores decreased from 7 to 2, mean pain relief increased for 30% to 80%, total opioid daily dose decreased from 53 to 36 mg parenteral morphine-eq, and nocturnal sleep increased from 2 to >6h (all figures are median values). Speech, eating, walking, and natural functions were generally not affected. Side effects such as tiredness and malaise, somnolence and sleep, feeling of coldness in the neck and skull base, transient post-spinal puncture headache, paresthesias, hoarseness, dysphagia, transient paresis of the upper/lower extremities, episodic miosis and conjunctival hyperemia, and transient orthostatic arterial hypotension were each observed in one or two patients. No patient presented clinical evidence of phrenic nerve paralysis. There was no nausea or vomiting. No persistent neurologic deficit or death could be attributed to the intracisternal pain treatment.

CONCLUSIONS

Continuous intracisternal infusion of bupivacaine may be a useful method in exceptional, well selected patients with refractory pain from the head and neck structures. Further studies are necessary to establish the indications and the safety of the method.

Comparison of cerebral blood flow measured by laser-Doppler flowmetry and hydrogen clearance in cats after cerebral insult and hypervolemic hemodilution

Laser-Doppler flowmetry provides a continuous measurement of blood flow without violating the natural state of circulation. The linearity of the laser-Doppler and hydrogen clearance methods of blood flow measurement were compared using a protocol that produced changes in cerebral blood flow that might be experienced in a neurosurgical setting. Cerebral blood flow was measured in both hemispheres of 12 adult cats during the snaring of one common carotid artery, the intracisternal injection of 5 mg of 5-hydroxytryptamine creatinine sulfate, and hypervolemic hemodilution, which produced a 25% reduction in blood hematocrit. The percentage of baseline laser-Doppler flowmetry and hydrogen clearance flows showed an acceptable degree of correlation (R2 = 0.762) over the range of cerebral blood flows measured. More rigorous analysis using Bland and Altman's difference against mean test showed that 10 minutes after hemodilution, the two methods displayed a level of variation outside the limits of agreement (-21.85 to 22.03%). Laser-Doppler flowmetry provided a noninvasive and continuous measure of blood flow, increasing the ability to observe instantaneous changes in cerebral microcirculation. However, laser-Doppler flowmetry did not record absolute blood flow, was affected by cerebral tissue shrinkage, and did not accurately measure flow under conditions of changed blood hematocrit.

Evidence for rapid fluid flow from the subarachnoid space into the spinal cord central canal in the rat

Horseradish peroxidase (HRP) was used as a CSF tracer in Sprague-Dawley rats. One group of rats received an injection of HRP in the cisterna magna and a second group was injected in the thoracic spinal subarachnoid space. The animals were sacrificed 0, 10 or 30 min after HRP injection by rapid perfusion with paraformaldehyde and glutaraldehyde. In both groups, there was rapid HRP labeling of brain and spinal cord perivascular spaces. HRP was present in the central canal in a pattern that was not consistent with flow from the fourth ventricle: in both groups there were segments of unlabeled central canal between the fourth ventricle and central canal segments containing HRP. HRP-labeled perivascular spaces were seen in the central gray matter adjacent to the central canal. There was a distinctive pattern of interstitial HRP between perivascular spaces and the central canal. The results suggest that there is a normal flow of fluid from the subarachnoid space, into the perivascular spaces, across the interstitial space and into the central canal. The function of this flow may be to clear metabolites from the interstitial space. The existence of such a flow would add considerable support to the theory that non-communicating syringomyelia develops in segments of central canal isolated by occlusion or stenosis at each end.

Apolipoprotein A-IV acts in the brain to inhibit gastric emptying in the rat

We have very recently shown that intracisternal injection of apolipoprotein A-IV (apo A-IV), a glycoprotein produced in the small intestine by fat, dose-dependently inhibited gastric acid secretion in pylorus-ligated conscious rats. These results suggest that apo A-IV acts centrally as a neuromodulator to inhibit gastric secretion. The present study was carried out to examine the hypothesis that apo A-IV acts centrally to alter gastric emptying. Rats fasted 24 h received intracisternal injection of apo A-IV and a liquid meal by oral intubation under brief isoflurane anesthesia. Gastric emptying of a liquid meal was determined by the phenol red method. Intracisternal injection of apo A-IV inhibited gastric emptying of a liquid meal in a dose-dependent manner (1.0-4.0 micrograms). On the other hand, apo A-I in a dose of 4 micrograms failed to change gastric emptying. Gastric emptying was not altered by intraperitoneal administration of apo A-IV in a dose of 15 micrograms. These results suggest that apo A-IV acts centrally to delay gastric emptying of a liquid meal. Together with our recent finding that apo A-IV acts centrally to inhibit gastric acid secretion, the present study supports our hypothesis that apo A-IV may be involved in lipid-induced inhibition of gastric function.

Effects of gamma-aminobutyric acid on regional vascular resistances of conscious spontaneously hypertensive rats

1. The regional vascular effects of a central injection of gamma-aminobutyric acid (GABA) in conscious spontaneously hypertensive rats (SHR) were compared with normotensive control rats (NCR), including Wistar-Kyoto rats (male, 10-20 weeks of age). One week or more after insertion of a cannula into the cisterna magna, an electromagnetic flow probe was implanted around one of five arteries, and a catheter for measurement of blood pressure and heart rate was inserted into the terminal aorta or common carotid artery. Cardiovascular changes were observed in the conscious animal after recovery from the surgery. Peripheral resistance was calculated as pressure divided by flow. 2. Ten min following intracisternal injection of 10 mu mol of GABA, mean arterial pressure and heart rate were significantly lowered (P < 0.05; t-test): - 29 and -16% (70 d.f.) in SHR versus -23 (116 d.f.) and -19% (112 d.f.) in NCR. Hindquarters, carotid, superior mesenteric and renal, but not coeliac, vascular resistances were significantly lowered (P < 0.05; t-test, 21, 9, 18 d.f.) in SHR. However, when comparing the effect of GABA injection in SHR and NCR, there were no significant differences in coeliac, carotid and hindquarters vascular resistances, but there were significant decreases in superior mesenteric and renal vascular resistances in SHR. 3. These results indicate that: (i) a cisternal injection of GABA in SHR decreases both peripheral vascular resistance and heart rate, and thereby lowers blood pressure; (ii) the vascular resistance of the superior mesenteric and renal vascular beds was more decreased in SHR than in NCR. This suggests that the GABAergic control of regional vascular resistance differs in the SHR and the NCR.

Central cardiovascular effects of acetylcholine in the conscious dog

1. The effects of central cholinomimetic drugs on cardiovascular and vasoactive hormonal responses (blood pressure, heart rate, catecholamines, vasopressin, atrial natriuretic factor, neuropeptide Y plasma levels and plasma renin activity) were investigated in conscious Beagle dogs. For this purpose a catheter was chronically implanted into each dog's cisterna magna to allow repeated central injections in the awake animals. 2. Intracisternal acetylcholine (20 micrograms kg-1) significantly increased systolic and diastolic blood pressure. These changes were accompanied by an initial short term tachycardia followed by a long lasting bradycardia. Intracisternal acetylcholine also increased noradrenaline, adrenaline and vasopressin plasma levels, decreased plasma renin activity but did not modify plasma levels of neuropeptide Y and atrial natriuretic factor. 3. The effects of acetylcholine were completely abolished by pretreatment with intracisternal injection of the muscarinic antagonist, atropine (5 micrograms kg-1) but not by the intracisternal injection of the nicotinic antagonist, mecamylamine (25 micrograms kg-1). 4. The present results demonstrate that there are qualitative and quantitative differences between the central cardiovascular effects of acetylcholine in conscious dogs compared to what we previously reported, using a comparable protocol, in anaesthetized dogs. Under both conditions, we observed a central cholinergically mediated increase in blood pressure secondary to an increase in sympathetic tone and vasopressin release but these responses were shorter (less than 10 min) in the conscious dogs than in anaesthetized dogs (more than 10 min). Moreover, we detected in the response to the central cholinergic stimulation in the conscious dogs a significant increase in plasma adrenaline levels and biphasic changes in heart rate which were not described previously in the anaesthetized dog.

Concentration of prostaglandin D2 in cerebrospinal fluid exhibits a circadian alteration in conscious rats

Cerebrospinal fluid (CSF) was withdrawn from the cisterna magna of unanesthetized conscious rats (n = 14) through a chronically implanted catheter, and prostaglandins (PGs) D2, E2, and F2 alpha were measured. From each rat, CSF samples were taken at different clock-hours of the day (1000, 1400, and 1800 hr) and night (2200, 0200, and 0600 hr) in succession at 76-hour intervals. The concentration of PGD2 alone exhibited a significant circadian fluctuation, with its peak value at 1400 hr (mean +/- SEM: 1197 +/- 361 pg/ml) and its lowest level at 0600 hr (438 +/- 106 pg/ml). Thus, the mean level of PGD2 during the daytime (903 +/- 162 pg/ml) was significantly higher than that during the night (503 +/- 78 pg/ml). The results obtained are consistent with the postulated role of PGD2, acting in the surface layer of the rostral basal forebrain, as an endogenous factor to promote sleep.

Assessment of delayed cerebral vasospasm using intracisternal echography--technical note

BACKGROUND

A new technique using intravascular ultrasound has been used for diagnosis of coronary artery in order to obtain intravascular echo images. In this study, an intracisternally positioned ultrasound catheter was introduced obtaining serial echo images of the first segment (MI) of the middle cerebral artery in order to detect cerebral vasospasm following subarachnoid hemorrhage (SAH).

METHODS

Thirteen patients were admitted to Osaka Neurological Institute with SAH due to ruptured intracranial aneurysm. All patients underwent surgical neck clipping on the day of admission. In each patient, an 8 Fr. ultrasound imaging catheter (Cardiovascular Imaging Systems, Inc. (CVIS), Sunnyvale, CA) was detained intracisternally adjacent to the M1 segment following neck clipping of the aneurysm and placement of cisternal drainage(s) in the prepontine and/or distal portion of the Sylvian fissure. In order to detain the mirro device near the M1 segment, the tip of a 2.0 cm cisternal drainage tube (SILASCON, E-3L-12, Kaneka Medix Co, Osaka, Japan) was attached to the tip of the intravascular ultrasound catheter with 3-0 silk suture. The tip was placed in the prechiasmal cistern.

RESULTS

Angiographic evidence of delayed vasospasm was obtained for three (23.1%) of the 13 patients. In one (33.3%) of the three patients who had angiographic evidence of vasospasm (25% stenosis), decrease in the inner diameter of the M1 segment was detected on the echo images, but in the other two (66.7%), no such decrease was noted on echo images. Angiographically identified vasospasm in the latter patients was associated with only 10% stenosis.

CONCLUSIONS

Intracisternally positioned ultrasound catheter can be used for intermittent measurement of the diameter of a target artery for detection of cerebral vasospasm after SAH.

Medullary thyrotropin-releasing hormone mediates vagal-dependent adaptive gastric protection induced by mild acid in rats

BACKGROUND & AIMS

Adaptive gastric protection is dependent on vagal pathways in rats. It is hypothesized that medullary thyrotropin-releasing hormone (TRH), known to regulate vagal function, is part of the brain mechanisms mediating adaptive gastric protection.

METHODS

Urethane-anesthetized rats were pretreated with either acute bilateral subdiaphragmatic vagotomy, sham operation, or intracisternal injection of purified control, TRH, or peptide YY antibody. Gastric lesions were assessed 75 minutes after orogastric administration of 1 mL of either vehicle or 0.35N HCl followed 15 minutes later by 0.6N or 1.0N HCl.

RESULTS

Injection of 0.6N and 1.0N HCl induced gastric lesions covering 23.1% +/- 2.7% and 37.8% +/- 3.3% of the corpus mucosa, respectively. Pretreatment with 0.35N HCl resulted in 67.3% and 50.5% reductions in gastric lesions induced by 0.6N and 1.0N HCl, respectively. Subdiaphragmatic vagotomy or intracisternal injection of TRH antibody increased gastric lesions induced by 0.6N HCl to 32.2% +/- 2.2% and 42.9% +/- 5.6%, respectively, and completely abolished the protective effect of 0.35N HCl pretreatment. Control or peptide YY antibody injected intracisternally did not alter the gastric protection induced by mild acid.

CONCLUSIONS

These results indicate that medullary TRH plays a role in the vagally mediated adaptive gastric protection induced by mild acid.

Involvement of alpha 2-adrenoceptors in the cardiovascular effects of moxonidine

The central sympathoinhibition caused by moxonidine has been explained by activation of alpha 2-adrenoceptors on the one hand, and by an action at imidazoline I1 receptors on the other hand. In order to examine these possibilities, effects of moxonidine were compared with those of 5-bromo-6-(2-imidazolin-2-ylamino)-quinoxaline (UK 14304), an alpha 2-adrenoceptor agonist with very low affinity for I1 receptors, in conscious rabbits. The interaction with yohimbine, an alpha 2-adrenoceptor antagonist with very low affinity for imidazoline I1 receptors, was also studied. Moxonidine 3-100 micrograms kg-1 and UK 14304 1-30 micrograms kg-1 i.v. elicited similar effects: they decreased arterial blood pressure after a transient increase, decreased renal sympathetic nerve activity (recorded with chronically implanted electrodes), decreased heart rate and decreased the plasma noradrenaline concentration. Yohimbine given i.v. antagonized the effects of moxonidine and of UK 14304 in a similar manner. Yohimbine injected into the cisterna magna (i.c.) prevented the hypotension but did not change the decrease in plasma noradrenaline and heart rate, again in the case of both moxonidine and UK 14304. The agreement of the effect patterns of moxonidine and UK 14304, and the similar antagonism of yohimbine against either drug, demonstrate involvement of alpha 2-adrenoceptors in their central sympathoinhibitory action. The resistance of the bradycardia and the plasma noradrenaline fall against yohimbine i.c. indicates a contribution of presynaptic alpha 2-adrenergic inhibition of transmitter release from postganglionic sympathetic neurons to the overall reduction of sympathetic tone.

[A case of accessory nerve neurinoma presenting an intracisternal tumor]

A case of neurinoma from the spinal accessory nerve which is located in the cisterna magna is reported. A 54-year-old woman was admitted to the institute in 1990 with complaints of headache, nausea and ataxic gait for several months. Plain CT showed dilation of the lateral ventricles and a mass of lower density in the cisterna magna. The capsule and septa of the mass were enhanced with contrast medium. MRI showed the mass was low intense on T1-weighted images and high intense on T2-weighted images. Gadolinium visualized the mass multicystic. V-P shunt was performed before tumor resection. Through suboccipital craniectomy and C1 laminectomy the tumor was removed. The tumor had a long neck attached to the right spinal accessory nerve and extended to the cisterna magna.

Central effects of endothelin on respiratory output during development

Both endothelin-1 protein and endothelin-1 specific binding sites have been identified in areas of the medulla oblongata involved in respiratory control. We examined whether endothelin acting centrally affects respiratory output during early postnatal life. We initially examined the effect of intracisternally administrated endothelin on respiratory output in 10 2- to 18-day-old piglets. Endothelin-1 administration at 50 nmol to 1 mumol caused respiratory inhibition. We subsequently examined whether this response is mediated through chemosensitive areas of the ventral medulla. Endothelin-1 was microinjected into specific ventral or dorsal medullary regions in 31 14- to 22-day-old piglets. Microinjection of endothelin-1 (10 fmol to 0.1 pmol) just above the hypoglossal roots, lateral to the pyramids, and within 1 mm from the surface (n = 24) attenuated respiratory output, and complete apnea occurred with 1 pmol in all animals. However, microinjection of endothelin-1 3 mm below the ventral surface (n = 5) and into the dorsal medulla (n = 3) had no inhibitory effect. Comparable doses of angiotensin II (n = 5) and norepinephrine (n = 5) microinjected into the endothelin-1 sensitive area also did not influence respiratory output. These effects of endothelin-1 were not altered by prior endothelin-B receptor blockade (IRL-1038) but could be reversed by endothelin-A receptor blockade (BQ-610). These results suggest that endothelin-1 release may cause ventilatory depression mediated through endothelin-A receptors located in the chemosensitive areas of the ventrolateral medulla.

Beta-endorphin may be a mediator of apnea induced by the laryngeal chemoreflex in piglets

To determine whether beta-endorphin is involved in the laryngeal chemoreflex, we initially injected 0.01-1 mg of beta-endorphin into the cisterna magna (i.c.m.) and registered the respiratory and cardiovascular patterns in 5-10-d-old piglets. From 0.1 to 1 mg of beta-endorphin i.c.m. induced a decrease in the minute volume, heart rate, and blood pressure within 15 min. Within the next 30 min respiratory pauses accompanied by blood pressure increases and reductions in heart rate developed, similar to the respiratory and cardiovascular pattern of the induced laryngeal chemoreflex. Based on these initial data, we decided to induce a laryngeal chemoreflex in piglets pretreated with 0.1 mg of beta-endorphin i.c.m (n = 6), 0.2 mg of beta-endorphin i.c.m. (n = 6), 0.1 mg of beta-endorphin i.c.m. and 100 micrograms/kg naloxone i.v. (n = 6), 100 micrograms/kg naloxone i.v. (n = 6), or water i.c.m. (n = 6). Because elevated levels of hypoxanthine in the vitreous humor may indicate hypoxia before death, we therefore measured the postmortem hypoxanthine levels in the vitreous humor. The laryngeal chemoreflex-induced apnea was shortened in the piglet group pretreated with water i.c.m and naloxone i.v. (p < 0.01) and in the piglet group pretreated with 0.1 mg of beta-endorphin i.c.m and naloxone i.v. (p < 0.05), but not significantly prolonged in the piglet groups pretreated with 0.1 or 0.2 mg of beta-endorphin i.c.m. when compared with the piglets pretreated with water i.c.m.(ABSTRACT TRUNCATED AT 250 WORDS)

Intracisternal rat pancreatic polypeptide stimulates gastric emptying in the rat

Pancreatic polypeptide (PP) has been shown to alter gastrointestinal functions, including increased gastric acid secretion and motility following brain stem injections of PP. The present study investigated the effect of an intracisternal injection of PP on the rate of gastric emptying. Additionally, the efficacy of the rat and bovine forms of the peptide was compared. Rats anesthetized with ether received an intracisternal injection of rat PP, bovine PP, or vehicle and, upon regaining consciousness, were fed a liquid test "meal." Intracisternal rat PP produced a marked enhancement in gastric emptying compared with control animals. Bovine PP, at doses equimolar to or three times greater than the effective rat PP dose, produced no change in gastric emptying. Pretreatment with systemic atropine prior to central injection of rat PP eliminated the stimulation of emptying, suggesting that PP acts through a cholinergic mechanism. When equimolar doses of rat or bovine PP were microinjected directly into the dorsal vagal complex, the region containing PP receptors, both were capable of stimulating antral motility. The response to bovine PP, however, was delayed and reduced compared with that seen following rat PP. The results suggest that rat PP strongly stimulates gastric emptying in rats and that bovine PP, depending on the route of administration, is either ineffectual or a weaker agonist for central PP receptors.

Central cardiovascular effects induced by intracisternal PACAP in dogs

The cardiovascular responses to intracisternally administered pituitary adenylate cyclase-activating polypeptide (PACAP) were investigated and compared with those of vasoactive intestinal peptide (VIP) in anesthetized dogs. Intracisternal administration of 10 nmol of PACAP-27 increased mean arterial blood pressure (MABP) significantly with a simultaneous increase of plasma arginine vasopressin and epinephrine concentrations. Intracisternal administration of VIP increased plasma arginine vasopressin concentration significantly but caused no appreciable change in MABP. Systemic infusion of the nonpeptide vasopressin V1 receptor antagonist OPC-21268 did not inhibit the PACAP-27-induced increase in MABP, whereas phentolamine, an alpha-adrenoceptor blocker, reversed the increase. Intracisternal pretreatment with the vasopressin V1 receptor antagonist [Pmp1, Tyr(Me)2]Arg8-vasopressin also inhibited the increase. These findings suggest that PACAP has a central pressor action by increasing sympathetic outflow, which is probably mediated by the vasopressinergic neural network. PACAP seems to play important roles in hormonal and neural control of systemic circulation.

Brain noradrenergic systems modulate the ceco-colonic myoelectric activity in rats

The role of the brain noradrenergic systems in the control of the ceco-colonic myoelectric activity was investigated in rats following lesions with intracerebroventricular (icv) or intracisternal (ic) injection of 6-hydroxydopamine (6-OHDA). Controls received the vehicle alone. The ceco-colonic myoelectric activity was recorded 3 weeks later in conscious rats chronically fitted with electrodes. After icv injection of 6-OHDA, lesions of rostral and caudal (spinal) noradrenergic systems were observed whereas only spinal noradrenergic systems were lesioned after ic injection. This differential pattern of lesions was followed by a differential pattern of ceco-colonic myoelectric activity. In fasted animals, a significant increase of the long spike burst (LSB) frequency (nb min-1) was observed after icv injection of 6-OHDA whereas no modification was observed after ic injection of the neurotoxic. After a 6-g pelleted rat diet, a significant increase of the LSB frequency was also observed in the icv lesioned group when compared to controls. No modification of the ceco-colonic noradrenergic innervation was observed, thus confirming the central selectivity of these lesions. Lesions of central noradrenergic systems modify the LSB frequency in rats; the rostral noradrenergic systems seem to play the major role.

Role of medullary I1-imidazoline and alpha 2-adrenergic receptors in the antihypertensive responses evoked by central administration of clonidine analogs in conscious spontaneously hypertensive rats

The antihypertensive action of clonidine analogs are generally ascribed to stimulation of medullary alpha 2-adrenergic receptors. Several recent studies have implicated the newly characterized class of imidazoline receptors as playing a more important role in this regard. In this study, a series of doses of four imidazoline and two nonimidazoline antihypertensive drugs were administered by intracisternal (i.c.) injection to freely moving spontaneously hypertensive rats. All six drugs produced a dose-dependent fall in mean arterial pressure (MAP) and heart rate (HR). The most potent agents in lowering MAP were the imidazoline agents, particularly moxonidine, a drug that has high affinity for I1-imidazoline receptors, but relatively low affinity for alpha 2-adrenergic receptors. There was a high correlation between the apparent binding affinity (Ki) for I1-receptors on membranes derived from bovine rostral ventrolateral medulla and the relative potency for lowering MAP after i.c. injection in spontaneously hypertensive rats. In contrast, no correlation existed between binding affinity values for alpha 2-adrenergic receptors derived from the same source and the antihypertensive response. The results of these experiments are consistent with a role for medullary I1-imidazoline receptors in mediating the antihypertensive action of clonidine and related imidazoline compounds in conscious hypertensive animals. The nonimidazoline agent, guanfacine, although a clinically effective antihypertensive agent, was not efficacious after i.c. injection. This discrepancy may be explained by an opposing pressor action or by a depressor action mediated by alpha 2-adrenergic receptors at an alternate site when the drug is peripherally administered. In contrast, the other nonimidazoline antihypertensive agent azepexole was fully efficacious after i.c. injection of the highest doses. Further studies may be necessary to determine whether drugs such as azepexole have a receptor target other than I1 or alpha 2-adrenergic receptors. We conclude that antihypertensive efficacy within the lower brainstem of conscious animals is predicted by interaction with I1-imidazoline but not alpha 2-adrenergic receptors.

Intracisternal administration of interleukin-1 beta attenuates naloxone-precipitated withdrawal in morphine-dependent mice

The effect of central administration of interleukin-1 beta on naloxone-precipitated withdrawal in morphine-dependent mice was studied. The degree of physical dependence on morphine was estimated by counting the number of jumps precipitated by naloxone, one of the typical withdrawal signs. Intracisternal (i.c.) administration of interleukin-1 beta (0.01-1 ng/5 microliters per mouse) to morphine-dependent mice 30 min prior to the injection of naloxone (10 mg/kg i.p.) decreased the number of jumps in a dose-dependent manner. The effect of interleukin-1 beta (1 ng) was significantly antagonized when it was co-administered with interleukin-1 receptor antagonist (1 microgram/mouse). These results suggest that centrally administered interleukin-1 beta could attenuate naloxone-precipitated withdrawal in morphine-dependent mice via interleukin-1 receptors in the brain. Co-administration of alpha-melanocyte-stimulating hormone (300 ng/mouse) or alpha-helical corticotropin-releasing factor (CRF)-(9-41), a CRF receptor antagonist (300 ng/mouse), with interleukin-1 beta also antagonized the inhibitory effect of interleukin-1 beta (1 ng). Moreover, i.c. administration of CRF (200 ng/mouse) significantly decreased the number of jumps.