Expression of the conditioned NK cell activity is beta-endorphin dependent

We are interested in identifying the pathways which are responsible for triggering the conditioned enhancement of natural killer (NK) cell activity. Earlier studies have suggested that central opioid(s) are involved in eliciting the expression of the conditioned NK cell activity. The purpose of this study was to identify the central opioid peptides that allow the central nervous system (CNS) to communicate with the immune system. Mediators that activate the efferent pathway of communication between the CNS and immune system was examined by injection of the mediator via the cisterna magna (CM). Conditioning was used as a tool to show that the bi-directional communication between the CNS and the immune system does take place. We found that beta-endorphin but not dynorphin could stimulate NK cell activity, when beta-endorphin or dynorphin was injected into the CM. In addition, when anti-beta-endorphin or anti-dynorphin antibody was injected into the conditioned animals via CM the conditioned response was blocked by anti-beta-endorphin but not by anti-dynorphin antibody. These observations suggest that beta-endorphin appears to be one of the signals that is induced in the brain at the CS recall step of the conditioned response to trigger the elevation of NK cell activity.

Intracisternal injection of TRH antibody blocks gastric emptying stimulated by 2-deoxy-D-glucose in rats

We evaluated the effect of 2-deoxy-D-glucose (2-DG) on gastric emptying of a non nutrient solution in conscious rats using a Phenol red method. Intravenous injection of 2-deoxy-D-glucose dose-dependently increased the rate of gastric emptying. This stimulatory action of 2-DG was abolished by subdiaphragmatic vagotomy. Intracisternal injection of thyrotropin-releasing hormone (TRH) antibody blocked intracisternal TRH and intravenous 2-DG-induced enhancement of gastric emptying but not the stimulation of gastric emptying induced by intracisternal pancreatic polypeptide. The TRH antibody injected intraperitoneally had no effect. These results suggest that endogenous TRH in the brain is involved in vagal-dependent stimulation of gastric emptying by 2-DG.

[Two cases of isolated ambient cistern hematoma after head injury]

This is a report of two cases of isolated ambient cistern hematoma after head injury. Isolated small hematomas in the ambient cistern after head injury are considered indirect evidence of brain stem injury. In such cases the initial neurological signs are often severe, but the ultimate prognosis is almost always good or excellent. Our patients showed hardly any neurological signs, and their head trauma was not very severe. Isolated ambient hematomas are the result of injury to small vessels or of mild contusions of the brain stem produced by the edge of the tentorium. In case 2, MRI revealed small, high signal intensity near the hematoma, and this sign was interpreted as evidence of mild brain stem injury. We think our patients had very mild brain injuries which were unaccompanied by diffuse axonal injury.

"Head-shaking syndrome" neurological deterioration during continuous head-shaking as an adjunct to cisternal irrigation for clot removal in patients with acute subarachnoid haemorrhage

To prevent cerebral vasospasm after aneurysmal subarachnoid haemorrhage, cisternal irrigation has been reported to be more effective when combined with continuous head-shaking (head-shaking method). The present study was conducted to evaluate the safety and preventative effect for vasospasm in patients treated with the head-shaking method. Six of 17 patients managed postoperatively by the original head-shaking procedure developed neurological deterioration related to the method: two had intracranial haematoma (one with acute interhemispheric subdural haematoma, and the other with cerebellar haemorrhage), two had acute brain swelling, and two failed to show abnormal findings on computed tomography. These pathological processes may be suitably referred to as "head-shaking syndrome". Delayed ischaemic neurological deficits associated with low-density lesions on computed tomography were demonstrated in five patients (29%). From these observations, the head-shaking method may not be as safe as described in the original articles, and is critically evaluated in terms of its preventative effect for cerebral vasospasm.

Suppression by the sumatriptan analogue, CP-122,288 of c-fos immunoreactivity in trigeminal nucleus caudalis induced by intracisternal capsaicin

1. The effects of an intravenously administered sumatriptan analogue were examined on c-fos-like immunoreactivity (c-fos-LI), a marker of neuronal activation, evoked within trigeminal nucleus caudalis (TNC) and other brain stem regions 2 h after intracisternal injection of the irritant, capsaicin (0.1 ml, 0.1 mM), in pentobarbitone-anaesthetized Hartley guinea-pigs. 2. C-fos-LI was assessed in eighteen serial sections (50 microns) using a polyclonal antiserum. A weighted average, reflecting total expression within lamina I, IIo of TNC was obtained from three representative levels (i.e., at -0.225 mm, -2.475 mm and -6.975 mm.). 3. Capsaicin caused significant labelling within lamina I, IIo, a region containing axonal terminations of small unmyelinated C-fibres, as well as within the nucleus of the solitary tract, area postrema and medial reticular nucleus. A similar distribution of positive cells was reported previously after intracisternal injection of other chemical irritants such as autologous blood or carrageenin. 4. Pretreatment with a conformationally restricted sumatriptan analogue (with some selectivity for 5-HT1B and 5-HTID receptor subtypes) CP-122,288, reduced the weighted average by approximately 50-60% (P < 0.05) in lamina I, IIo at > or = 100 pmol kg-1, i.v., but did not decrease cell number within area postrema, nucleus of the solitary tract or medial reticular nucleus. A similar pattern was reported previously following sumatriptan, dihydroergotamine or CP-93,129 administration after noxious meningeal stimulation. 5. We conclude that modifications at the amino-ethyl side chain of sumatriptan dramatically enhance the suppression of c-fos expression within TNC, a finding consistent with its remarkable potency against neurogenic plasma protein extravasation within dura mater. CP-122,288 and related analogues may serve as an important prototype for drug development in migraine and related headaches.

Neurotoxicity of non-ionic X-ray contrast media after intracisternal administration in rats

The neurotoxicity of an X-ray contrast medium appears inversely related to the hydrophilicity of the agent. To further test this hypothesis, four non-ionic X-ray contrast agents, differing in hydrophilicity, (ioversol, iopromide, iohexol and iopamidol) were injected into the cisternal magna of ether-anesthetized rats. Iopromide demonstrated an acute median lethal dose of 122 mg I/kg. Other signs of toxicity included convulsions, apnea, dyspnea and hypoactivity. In contrast, ioversol, iohexol and iopamidol caused no deaths when administered intracisternally, up to a dose of 1000 mg I/kg. Animals treated with these nonionic agents displayed signs of convulsions, apnea, dyspnea, chewing and hypoactivity. Iopromide possesses a hydrophilicity (e.g., water to octanol partition coefficient) approximately 8.5 times smaller than ioversol, 4.6 times smaller than iohexol and 2.3 times smaller than iopamidol. These data support the hypothesis that tri-iodinated X-ray contrast materials with smaller degrees of hydrophilicity produce greater toxicity to the central nervous system.

Cardiovascular effects of agmatine, a "clonidine-displacing substance", in conscious rabbits

Agmatine has been identified as a "clonidine-displacing substance" in extracts from bovine brain. We studied its effect on cardiovascular regulation and the role played in this effect by alpha 2-adrenoceptors. In conscious rabbits, agmatine 10 micrograms kg-1 injected intracisternally (i.c.) caused no change, whereas agmatine 30, 100 and 300 micrograms kg-1 i.c. increased renal sympathetic nerve firing, the plasma concentration of noradrenaline and adrenaline and arterial blood pressure. Heart rate tended to be decreased. Yohimbine 1.5 micrograms kg-1 i.c. caused no change, whereas yohimbine 5, 15 and 50 micrograms kg-1 increased renal sympathetic nerve activity, the plasma concentration of noradrenaline and adrenaline, blood pressure and heart rate. In rabbit brain cortex slices preincubated with [3H]-noradrenaline, agmatine 1 to 100 microM did not modify the electrically evoked overflow of tritium (either 4 pulses at 100 Hz or 36 pulses at 3 Hz). The evoked overflow was reduced by 5-bromo-6-(2-imidazolin-2-ylamino)-quinoxaline (UK 14304) 0.03 to 30 nM (4 pulses at 100 Hz), and this inhibition was not affected by agmatine 10 and 100 microM. Agmatine did not change the basal efflux of tritium. The results show that agmatine, like yohimbine, causes central sympathoexcitation when given i.c., but agmatine differs from yohimbine in that it does not increase heart rate. Agmatine acts neither as an agonist nor as an antagonist at the alpha 2-autoreceptors in rabbit brain cortex. alpha 2-Adrenoceptors, therefore, are probably not involved in its cardiovascular effects.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of intracisternal injection of somatostatin analog receptor subtypes 2, 3 and 5 on gastric acid secretion in conscious rats

Somatostatin (SST) and its analogs injected into the CSF induce different gastric acid response patterns. Five SST receptors have been characterized (SSTR-1 to -5). We studied the influence of selective SSTR-2, -3 and -5 ligands on basal gastric acid secretion after intracisternal (i.c.) injection in conscious rats equipped with chronic gastric and i.c. cannulae. Compared with pre-injection level, the SSTR-3 agonist, BIM-23056 (1 microgram) increased acid secretion by 274 +/- 43% while the SSTR-2 agonist, DC 32-87 (1 microgram) inhibited acid secretion by 50.7 +/- 13.3%. SST-14 (1 microgram), the SSTR-5 agonist, BIM-23052, (0.5-1 microgram), SSTR-3 (0.5 micrograms) and -2 (0.5 microgram) or vehicle injected i.c. did not modify basal acid secretion. These results show that the activation of brainstem SSTR-3 receptors stimulate and SSTR-2 inhibit basal gastric acid secretion in conscious rats with chronic gastric fistulae.

Neural tolerability of iodixanol in mice and dogs after single and repeated intracisternal administration

The neural tolerability of iodixanol has been assessed in studies in mice and dogs. The animals received up to 4 injections in the cisterna cerebellomedullaris while under light anesthesia. Iotrolan was included as a reference study in 1 study. The observations comprised assessment of clinical behavior, cerebrospinal fluid analysis, hematology, clinical chemistry and/or macroscopic and microscopic examination at necropsy. In addition, the repeated-dose dog study, urinalysis and opthalmoscopy were performed, electrocardiograms obtained, and respiratory rate, blood pressure and rectal temperature measured. Clinical signs and minor pathological changes caused by the injection procedures were seen in all studies in some animals treated with iodixanol as well as in control animals. Single (2.0 g I/kg) and repeated (0.960 g I/kg) intracisternal administration of iodixanol to mice caused no significant toxicological effects. Two dogs treated with a high dose of iodixanol (0.256 g I/kg; 0.8 ml/kg) had pathological changes (meningeal inflammation and/or necrosis) that were more severe than those observed in control dogs. Single and repeated intracisternal administration of 0.128 g I/kg (0.4 ml/kg) of iodixanol to dogs, however, caused no significant toxicological effects. Apart from the findings in the 2 dogs, the neurological and neuropathological changes elicited by iodixanol were similar to those induced by control or reference substances. The results from these intracisternal toxcity studies in mice and dogs indicate a significant margin of safety regarding the use of iodixanol in clinical intra-thecal indications.

Cerebral arterial spasm--a clinical review

A review of the literature on cerebral vasospasm after aneurysmal subarachnoid haemorrhage (SAH) has shown that angiographic vasospasm occurs in 67.3% of cases when angiography is timed for the highest likelihood, and delayed ischaemic deficit or symptomatic vasospasm in 32.6%. The presence of vasospasm has a marked effect on overall outcome of SAH, and the outcome of delayed ischaemia itself is in about one-third death and in one-third permanent deficit. Management with fluid loading or induced hypertension and with calcium antagonists has been reported widely for both prevention and treatment, and can reduce the incidence and improve the outcome of vasospasm. Other forms of treatment including tissue plasminogen activator, aminosteroids and transluminal angioplasty also appear useful. In spite of these improved therapeutic possibilities, large numbers of patients are still being reported in whom no specific treatment is used.

Plasma levels of luteinizing hormone during hyperprolactinemia: response to central administration of antagonists of corticotropin-releasing factor

Since high concentrations of prolactin (PRL) enhance the hypothalamic release of corticotropin-releasing factor (CRF), and CRF decreases the hypothalamic secretion of luteinizing hormone (LH)-releasing hormone (LHRH), it could be that CRF is involved in the suppressed secretion of LH during hyperprolactinemia. The aim of this study was to explore this possibility in hyperprolactinemic male rats. Hyperprolactinemia, induced by insertion of 3 pituitary glands under the kidney capsule, decreased plasma LH levels by 68% and caused a 2-fold increase in plasma corticosterone. Intracisternal administration of the CRF antagonist alpha-helical CRF(9-41) induced both in pituitary-grafted rats and in normoprolactinemic controls a 2 to 3-fold increase of LH in the plasma sample taken 1 h after injection of alpha-helical CRF(9-41). Plasma levels of LH in pituitary-grafted rats were 2-3 times higher during intracerebroventricular infusion for 7 days with CRF antiserum than during saline infusion. Furthermore, after infusion of CRF antiserum for 7 days into the lateral brain ventricle plasma LH levels had increased by 270% in normoprolactinemic male rats. These results indicate that hypothalamic CRF is involved in the control of LH release in male rats. To further investigate whether CRF is involved in the effect of PRL on LH secretion, we infused PRL, alone or together with CRF antiserum, for 7 days into the lateral brain ventricle of normoprolactinemic male rats. After 7 days of PRL infusion, LH levels had decreased by 45%, whereas plasma corticosterone was 150% higher. This action of PRL on LH and corticosterone was prevented when besides PRL also CRF antiserum was infused.(ABSTRACT TRUNCATED AT 250 WORDS)

Central neuropeptide Y enhances bile secretion through vagal and muscarinic but not nitric oxide pathways in rats

Neuropeptide Y (NPY) acts in the central nervous system to regulate gastrointestinal functions in rats and dogs. The effects of intracisternal injection of NPY on bile secretion and biliary components were investigated in urethane-anesthetized rats with bile duct cannula. Intracisternal NPY (0.02-0.12 nmol) dose-dependently increased bile secretion by 9.2-19.5%. The secretory response occurred within the first 20-40 min and lasted for the 120-min observation period. Intravenous injection of NPY (0.12 nmol) did not modify bile secretion under identical conditions. Biliary bile acid, phospholipid, and cholesterol secretion were not modified by intracisternal injection of NPY (0.12 nmol), whereas bicarbonate was increased by 19.0 +/- 1.7% from 40 to 120 min after NPY injection. Cervical cord transection at the C6 level, acute bilateral adrenalectomy (-120 min), or injection of NG-nitro-L-arginine methyl ester (10 mg/kg, IV, -15 min), an inhibitor of nitric oxide biosynthesis, did not alter intracisternal NPY (0.12 nmol)-induced stimulation of bile secretion. Atropine (2.0 mg/kg, IP, -30 min) and bilateral cervical vagotomy (-120 min) completely abolished the stimulatory effect of intracisternal NPY (0.12 nmol) on bile secretion. These findings indicate that NPY acts in the brain to stimulate bicarbonate-dependent bile secretion through vagal and muscarinic pathways and suggest that peptides in the central nervous system may be involved in the vagal regulation of bile secretion.

An experimental model of leptomeningeal metastases employing rat mammary carcinoma cells

Five percent of patients dying with breast cancer have leptomeningeal metastases (LM) but current therapy is of only marginal benefit. Therefore, an experimental model of LM from breast cancer was developed to facilitate the development of novel therapies. Cell suspensions of 13762 MAT BIII rat mammary carcinoma cells are injected into the cisterna magna of adult, female Fischer 344 rats under general anesthesia. 10-12 days after the injection of 2 x 10(5) viable cells, animals develop neurologic signs, including ataxia, paralysis and spontaneous rotation. Histologically, tumor cells can be seen in the subarachnoid space over the surface of the brain and spinal cord and within the ventricles. Tumor cells do not invade the brain parenchyma. Collections of tumor cells are extensively infiltrated by macrophages and CD8-positive (suppressor/cytotoxic) T cells, but by few CD4-positive (helper) T cells. MAT BIII cells therefore provide a model of LM from breast cancer with a reproducible clinical course and histologic features. The tumor elicits a cellular immune response and can be useful in exploring biologic therapies for leptomeningeal metastases.

Intracisternal injection of apolipoprotein A-IV inhibits gastric secretion in pylorus-ligated conscious rats

BACKGROUND/AIMS

Fat feeding increases not only serum but also cerebrospinal fluid concentration of apolipoprotein (apo) A-IV, a protein produced mainly by the small intestine in the rat. We hypothesized that apo A-IV may have a central effect on gastric secretion.

METHODS

Gastric juice was collected by the pylorus ligation method. Rats underwent pylorus ligation and received intracisternal injection of apo A-IV under brief isoflurane anesthesia. Two hours after the injection, gastric juice was collected and gastric acid output determined.

RESULTS

Intracisternal injection of 0.5 microgram apo A-IV had no effect on gastric secretion. However, gastric acid secretion was significantly inhibited by intracisternal injection of 1 microgram apo A-IV. Furthermore, intracisternal administration of higher doses of apo A-IV (2.0 and 4.0 microgram) resulted in greater inhibition of gastric acid secretion in a dose-dependent manner. On the contrary, 4 micrograms of apo A-I intracisternally injected failed to inhibit gastric acid secretion. Intraperitoneal administration of 15 micrograms of apo A-IV did not alter gastric secretion.

CONCLUSIONS

These results suggest that apo A-IV may act in the brain to inhibit gastric acid secretion. Apo A-IV might be a central enterogastrone, which is a gastric inhibitor produced by the small intestine in response to fat feeding.

Cerebral vasospasm caused by cisternal injection of polystyrene latex beads in rabbits is inhibited by a serine protease inhibitor

During subarachnoid hemorrhage (SAH), coagulated blood in the subarachnoid space may be regarded as foreign by the immune system. To investigate how cerebral arteries are affected by activation of the host immune system, foreign body, polystyrene latex beads were injected into the cerebrospinal fluid (CSF) space of rabbits, and the caliber changes of the basilar arteries were studied for 7 days by angiography. Prolonged arterial narrowing peaking on day 2 was observed after cisternal injection of the beads. The increase in peak narrowing correlated with an increase in the number of beads injected. The course of the change in vessel caliber over 7 days was similar to that seen in cerebral vasospasm caused by SAH. Also investigated was the preventive effect of the synthetic serine protease inhibitor, FUT-175 on the arterial narrowing caused by the cisternal injection of the latex beads. The administration of FUT-175 significantly prevented latex beads-induced vasospasm (p < 0.01). The possible role of a non-specific immune response is discussed, and also the role of the serine protease cascades in the development of cerebral vasospasm.

Pyroglutamyl peptidase II activity is not in the processes of bulbospinal TRHergic neurons

Pyroglutamyl peptidase II (PPII) is a neuronal ectoenzyme involved in released thyrotropin-releasing hormone (TRH) inactivation. In an attempt to define if it is present in the pre or postsynaptic membrane, we induced neuronal degeneration of serotonin-TRHergic cells that project from raphe nuclei to the spinal cord. 2-4 weeks after intracisternal injection of 5,7-dihydroxytryptamine, TRH levels decreased over 70% in the cervical, thoracic or lumbar regions of spinal cord. In contrast, no change of PPII activity was observed. Longer times after injection (6-8 weeks), a 59-66% increase in activity was detected in the lumbar region. These data suggest that PPII is not localized in these TRHergic neurons but probably in the target cells.

Dysfunction of nitric oxide in the spastic basilar arteries after subarachnoid hemorrhage

The function of nitric oxide in spastic cerebral arteries after subarachnoid hemorrhage (SAH) was angiographically investigated in dogs. On days 4 and 7, after two intracisternal injections of autologous blood, higher concentrations of L-arginine than those of endogenous L-arginine in the cerebrospinal fluid produced a transient vasodilation of the spastic basilar artery, whereas NG-monomethyl-L-arginine (L-NMMA) produced no significant vasoconstriction. The vasodilator effect of L-arginine after SAH was stronger on day 4 than day 7, but less than that in intact dogs. Vasopressin, which is known to activate the endothelial L-arginine pathway, could induce a vasodilation only after the treatment with L-arginine. Intracisternal injection of superoxide dismutase (SOD), which caused no effect by itself, enhanced the duration of the vasodilator effect of L-arginine on the basilar artery on day 4 and both the magnitude and duration of that effect on day 7. Thus, the basal release of nitric oxide was impaired after SAH, but the ability to synthesize nitric oxide in the vascular wall was not abolished. Enhancement of L-arginine's effect by SOD suggested that the inactivation of nitric oxide by superoxide anion contributed to the development of vasospasm.

Pharmacokinetics of fluconazole in cerebrospinal fluid and serum of rabbits: validation of an animal model used to measure drug concentrations in cerebrospinal fluid

Complete concentration-time data describing the pharmacokinetics of fluconazole in the cerebrospinal fluid (CSF) following a single dose are not available for humans or animals. We studied the pharmacokinetics of fluconazole with an indwelling intracisternal needle as described by R.G. Dacey and M.A. Sande (Antimicrob. Agents Chemother. 6:437-441, 1974). To determine whether the presence of an intracisternal needle alters pharmacokinetics in the CSF, we validated this model with uninfected rabbits by measuring pharmacokinetic constants following direct intracisternal and intravenous administration of fluconazole. Following direct injection, there was no alteration of elimination rates in the CSF with increasing sample number or time. Following intravenous administration, the penetration and kinetic constants were the same in individual animals from which multiple CSF samples were obtained as in a composite subject constructed by pooling virgin samples from different animals. The presence of the intracisternal needle did not alter CSF chemistry or leukocyte counts, and erythrocyte contamination was < 0.001%. While drug concentrations were measured by a microbiological assay, we also compared the sensitivity and reproducibility of a high-performance liquid chromatography (HPLC) assay with those of the microbiological assay. Following a single intravenous dose, the maximum concentration of the drug in serum, the time to maximum concentration of the drug in serum, the terminal elimination half-life in the CSF, and the percent penetration by fluconazole were 6.12 micrograms/ml, 1 h, 9.0 h, and 84.3%, respectively. We conclude that the sampling of CSF via an indwelling needle does not alter fluconazole pharmacokinetics, cause inflammation, or alter chemical parameters; that the microbiological assay is at least equivalent in sensitivity and reproducibility to the HPLC assay; and that robust parameters describing the pharmacokinetics of fluconazole are possible with this model.

Effects of vasopressin on regional cerebral blood flow in dogs

Vasopressin may regulate the regional cerebral blood flow (rCBF) via two balancing effects: increased flow from the vessels dilated by nitric oxide from the endothelium, and decreased flow from the vessels contracted by direct stimulation of smooth muscle. The effect on the rCBF in anesthetized dogs following the intracisternal or intraarterial administration of vasopressin was investigated by laser flowmetry with the device placed on the dura over the parietal cortex. The intracisternal injection of 1 nmol vasopressin significantly increased the rCBF to 145.3 +/- 27.3% of base line. In contrast, the intravertebral arterial injection of vasopressin had no significant effect on the rCBF. This can be explained by a difference in the affected vasculature; mainly large vessels in the subarachnoid space vs. whole vascular system supplied by the vertebral artery. The intracisternal injection of 10 mumol of NG-monomethyl-L-arginine (L-NMMA) reduced the rCBF; pretreatment with this agent significantly suppressed the elevation in rCBF induced by vasopressin. The intraarterial injection of L-NMMA reduced the rCBF more than its intracisternal administration. It also suppressed the rCBF induced by vasopressin.

Change in the concentrations of amino acids in cisternal CSF of patients with essential tremor

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Quantitative autoradiography of 5-hydroxytryptamine1A binding sites in rats with chronic neonatal 5,7-dihydroxytryptamine lesions

We recently reported that rats with elevated brainstem serotonin (5-HT) concentration and 5-HT transporter binding site density after neonatal 5,7-dihydroxytryptamine (5,7-DHT) lesions made by intraperitoneal (i.p.) injection exhibited more myoclonic supersensitivity to the 5-HT1A agonist 8-OH-DPAT than those with decreased brainstem 5-HT and 5-HT transporter sites following intracisternal 5,7-DHT (i.c.) injection. To investigate the role of 5-HT1A receptors in these differences, we labelled 5-HT1A binding sites autoradiographically with [3H]8-OH-DPAT 4 months after i.p. or i.c. 5,7-DHT or saline in the first week postnatal. The regional distribution of 5-HT1A sites conformed to previous reports of highest receptor densities in hippocampus (CA1, dentate gyrus), septal nuclei, dorsal and median raphe, mammillary body, and certain cortical regions (cingulum, claustrum). 5-HT1A binding was significantly decreased (-87%) in the dorsal raphe after i.c.-made 5,7-DHT lesions. No reductions were found after lesions made by i.p. injection compared to controls, but rather a 246% increase in area of 5-HT1A binding extending from the dorsal raphe was observed. These changes in 5-HT1A binding sites in the dorsal raphe in the chronic phase of 5,7-DHT lesions may contribute to the different behavioral consequences of the route of neonatal 5,7-DHT injection.

Intracisternal administration of SKF-38393 and SCH-23390: behavioral effects in the rat fetus

The dopamine D1 agonist SKF-38393 and the D1 antagonist SCH-23390 were administered into the central nervous system of the E21 rat fetus via intracisternal (IC) injection. IC injection of SKF-38393 promoted a dose-dependent increase in fetal motor activity, principally including movements of the forelimbs, head, and body trunk. IC injection of SCH-23390 did not affect overall activity, but selectively suppressed forelimb, rearlimb, and head movements and promoted an increase in mouthing, licking, and facial wiping. Administration of SCH-23390 after IC injection of SKF-38393 was effective in completely reversing the behavioral effects of the D1 agonist. These findings suggest that central manipulation of dopamine D1 receptors can have direct and potent behavioral effects in the term rat fetus.

Comparison of antinociception induced by supraspinally administered L-arginine and kyotorphin

1. Intracerebroventricular (i.c.v.) or intracisternal (i.cist.) administration of kyotorphin (KTP), an endogenous Met-enkephalin releaser, at 5 micrograms per mouse, and L-arginine (L-Arg), a possible KTP precursor, at 30 micrograms per mouse, elicited antinociception in mice to a similar extent, as assessed by the tail-flick test. 2. Intracisternal preadministration of anti-KTP serum abolished the effect of i.cist. KTP and i.c.v. or i.cist. L-Arg, but not of i.c.v. KTP. 3. The antinociceptive effects of i.cist. KTP and of i.c.v. or i.cist. L-Arg disappeared in reserpinized mice, whereas the effect of i.c.v. KTP was unaffected by treatment of mice with reserpine. 4. Intrathecal (i.t.) phentolamine markedly reduced the antinociception induced by i.cist. KTP and by i.c.v. or i.cist. L-Arg, but not by i.c.v. KTP. 5. Intrathecal methysergide attenuated the antinociceptive effects of i.cist. KTP, but not of i.c.v. KTP and i.c.v. or i.cist. L-Arg. 6. These results suggest that the antinociception produced by i.cist. KTP, but not by i.c.v. KTP, is mediated by the brainstem-spinal noradrenergic and 5-hydroxytryptaminergic systems, and that L-Arg given i.c.v. or i.cist. increases KTP formation in the lower brain, possibly the brainstem, resulting in antinociception mediated by the descending noradrenergic system. Therefore, the regional distribution of KTP receptors and KTP synthetase in the brain does not appear to be common.

Sonographic diagnosis of cisternal subarachnoid hemorrhage in the premature infant

PURPOSE

To evaluate sonographic criteria for the diagnosis of subarachnoid, and particularly cisternal, hemorrhage in the preterm infant.

METHODS

The subarachnoid cisterns were studied on cadaveric anatomic sections and on postmortem ultrasonograms, as well as on in vivo ultrasonograms of healthy neonates. Based on the normal ultrasound appearances of these cisterns, criteria were developed for the recognition of abnormal cisternal fluid collections, which strongly suggest the presence of subarachnoid hemorrhage in the premature infant. These criteria were evaluated prospectively in a group of 63 preterm infants who underwent subsequent autopsy.

RESULTS

In the 63 infants with neuropathologic verification, increased echogenicity and/or increased echo-free content of the subarachnoid cisterns correctly predicted subarachnoid hemorrhage with an accuracy of 75%, sensitivity of 69%, and specificity of 93%. The positive and negative predictive values were 97% and 46%, respectively. In 47% of the cases, ultrasound correctly detected cisternal subarachnoid hemorrhage before intraventricular hemorrhage could be diagnosed.

CONCLUSION

A highly specific, although somewhat insensitive, sonographic diagnosis of subarachnoid hemorrhage can be made from the appearance of the subarachnoid cisterns. The diagnosis of subarachnoid hemorrhage may predate the ultrasound diagnosis of intraventricular hemorrhage and may alert the neonatologist to the need for follow-up sonograms in the absence of ultrasound evidence of intraventricular hemorrhage.

Intracisternally injected galanin-(1-15) modulates the cardiovascular responses of galanin-(1-29) and the 5-HT1A receptor agonist 8-OH-DPAT

In view of the demonstration of specific binding sites for [125I]galanin-(1-15) in several brain areas including the nucleus of the solitary tract, possibly indicating the existence of multiple galanin receptor subtypes, the effects of intracisternal injections of galanin-(1-15) on cardiovascular parameters were studied. The effects of co-injections of galanin-(1-15) and galanin-(1-29) and co-injections of galanin-(1-15) and the 5-HT1A receptor agonist 8-OH-2-(di-n-propylamino)tetralin (8-OH-DPAT) were also evaluated. Galanin-(1-15) produced a significant increase in mean arterial blood pressure (maximum effect 10% at 3 nmol of galanin-(1-15)) and in heart rate (maximum effect 12% at 1 nmol). When threshold doses of galanin-(1-15) (0.1 nmol) and galanin-(1-29) (3 nmol) were injected simultaneously they elicited an increase in mean arterial blood pressure. The vasodepressor response induced by an ED50 dose of 8-OH-DPAT (6 nmol) was not modulated by a threshold dose of galanin-(1-15), but the increase in heart rate area induced by galanin-(1-15) alone was no longer observed. When threshold doses of both galanin-(1-15) and 8-OH-DPAT (0.3 nmol) were co-injected a vasodepressor response developed and on heart rate a tachycardic response was seen in the peak effects and the overall tachycardic response induced by galanin-(1-15) was sustained. The results show a different role for galanin-(1-15) as compared with galanin-(1-29) in central cardiovascular control.(ABSTRACT TRUNCATED AT 250 WORDS)

Failure of intracisternal tissue plasminogen activator to prevent vasospasm in certain patients with aneurysmal subarachnoid hemorrhage

Recent experimental and clinical reports suggest that the intracisternal administration of recombinant tissue plasminogen activator (tPA) within 72 hours of subarachnoid hemorrhage decreases the incidence of severe angiographic and clinical vasospasm. In this report, we present four of eight patients with aneurysmal subarachnoid hemorrhage who developed angiographic and clinical vasospasm with delayed neurological deterioration, despite the use of intracisternal tPA after early aneurysm clipping. One patient did not clear her massive subarachnoid hemorrhage with tPA; one patient had extremely poor collateral flow with occlusion of one cervical internal carotid artery and 80% stenosis of the other cervical internal carotid artery; the other two patients had a subarachnoid hemorrhage 7 to 12 days after their sentinel hemorrhage. Three patients ultimately made excellent or good recoveries, and one was left with hemiparesis. The four other patients treated by this protocol did not develop vasospasm. We conclude that intracisternal tPA may not prevent vasospasm in certain patients. This may relate to inadequate clearing of the subarachnoid clot, pre-existing poor collateral supply, or the occurrence of prior subarachnoid hemorrhage.

Centrally induced vasopressor and sympathetic responses to a novel endogenous peptide, adrenomedullin, in anesthetized rats

Possible central actions of adrenomedullin were explored and compared with the peripheral effects by injecting it into the lateral ventricle, cisterna magna, and femoral vein in urethane-anesthetized rats. Adrenomedullin, 1.0 to 3.0 nmol/kg, injected intravenously (i.v.), caused a transient vasodepression of about 10 to 30 mm Hg, dose dependently, which lasted for < 15 min. On the other hand, intracerebroventricular (ICV) and intracisternal (IC) injections of adrenomedullin elicited sustained elevations of arterial pressure of gradual onset, dose dependently; the arterial pressure started to rise at about 3 min after the injection, and gained peak response after > 20 min. The pressor response lasted for > 2 h. Heart rate was not significantly influenced by these doses of adrenomedullin. The abdominal sympathetic outflow was markedly increased in relation to the blood pressure elevation. The time-course of the responses was quite similar with both ICV and IC injections. Hypotensive effects of i.v. injected adrenomedullin was partially attenuated, and the centrally induced vasopressor responses were abolished by the pretreatment with human calcitonin gene-related peptide (hCGRP)-receptor antagonist, hCGRP(8-37). These findings indicate that the receptors for adrenomedullin exist in the brain, and that the receptor site may be anatomically far from the surface of the brain and the ventricular system because the onset of the pressor response was delayed. Or, CGRP and adrenomedullin may share the same receptors, particularly in the brain.

Role of the spinal cord in intracisternal beta-endorphin-evoked suppression of liver DNA synthesis in 10-day-old rats

Previously, we have shown that intracisternal (i.c.) administration of beta-endorphin (an opioid peptide naturally occurring in the brain) to preweanling rats markedly decreases DNA synthesis (an index of cell proliferation) in both brain and liver. This observation is consistent with our hypothesis that endogenous CNS beta-endorphin plays an important role in controlling postnatal growth. The current research specifically undertook to investigate, in 10-day-old rats, whether or not i.c. beta-endorphin-evoked suppression of liver DNA synthesis is actually mediated by spinal opioid receptors and/or by descending endorphinergic pathways. In contrast to the i.c. route of administration, beta-endorphin given directly into the spinal subarachnoid space via intrathecal (i.t.) injection did not alter liver DNA synthesis, yet was able to evoke profound antinociceptive responses. This demonstrates that intracisternally applied beta-endorphin exerts its effect on liver DNA by acting at supraspinal sites, and not by directly stimulating spinal opioid receptors after diffusion from its intracerebral site of injection. As it is possible that beta-endorphin's supraspinal actions may activate a descending inhibitory endorphinergic pathway to reduce DNA synthesis, we conducted studies in rat pups administered naloxone intrathecally. Naloxone i.t. was completely ineffective in preventing beta-endorphin i.c. from inhibiting liver DNA synthesis. On the other hand, i.t. coinjection of naloxone plus beta-endorphin was able to block the analgesic response, while their i.c. coinjection reversed the DNA effect. The results from these studies indicate that opioid systems within the spinal cord do not play a major role in mediating CNS beta-endorphins regulation of DNA synthesis in peripheral tissues.(ABSTRACT TRUNCATED AT 250 WORDS)

Pupillary changes after intracisternal injection of papaverine

Pupillary changes attributed to intracisternal papaverine injection were observed in three patients who underwent pterional craniotomy and clipping of a supratentorial aneurysm in which the oculomotor nerve was not manipulated. A fixed and dilated pupil on the side of the craniotomy lasted 2 to 4 hours after intracisternal papaverine instillation. These observations suggest that a dilated, nonreactive pupil subsequent to an uncomplicated pterional craniotomy for aneurysm, in which oculomotor nerve trauma has not occurred, may not be an ominous finding but may represent a transient phenomenon related to intracisternal papaverine injection.

Microdialysis analysis of effects of loop diuretics and acetazolamide on chloride transport from blood to CSF

With the hypothesis that the NaCl cotransporter in mammalian choroid plexus (CP) has a role in CSF formation, we postulated that loop diuretic agents would curtail transport of Cl from blood to CSF. Microdialysis in the cisterna magna of Sprague-Dawley rats was used to assess the ability of furosemide and ethacrynic acid (i.e. loop agents that interfere directly with cotransport) to inhibit 36Cl transport from blood to CSF over a 3-h period. Cl uptake by CSF was quantified as % volume of distribution (Vd) of 36Cl, i.e. 100 x cpm/g CSF divided by cpm/ml plasma. Uptake curves of Vd vs. time were constructed for the various treatments; then, to compare drug effects, the curves were analyzed for: (i) the early slope of uptake (Kin), (ii) the steady-state value for Vd, and (iii) the area-under-curve (AUC). Assessment of the curve parameters collectively revealed that at 5 mg/kg, both furosemide (FUR) and ethacrynic acid (EA) reduced Cl penetration into CSF by one quarter; at 50 mg/kg, these loop agents decreased Cl uptake by about a third. On the other hand, 50 mg/kg of the carbonic anhydrase inhibitor, acetazolamide, reduced Cl uptake into CSF by 55-60%. Thus, NaCl cotransport inhibitors maximally reduced Cl transport in the rat by about 35%; this inhibition was less extensive than that brought about by acetazolamide, which interferes with CSF secretion by a different mechanism.

Anti-nociceptive effects of oxytocin in rats and mice

The existence of neural opioid-mediated networks that are specific for the modulation of nociception is well established. Parallel non-opioid pathways exist, but their underlying physiology is little known. We now report that oxytocin administered intraperitoneally to rats, and intraperitoneally or intracisternally to mice has an anti-nociceptive effect, which is related to the activation of descending anti-nociceptive pathways. This anti-nociceptive effect can be reversed by an oxytocin antagonist but not by the opioid antagonist naloxone. The anti-nociceptive effect of oxytocin is not directly dependent on the activation of serotonergic pathways or to changes in temperature. Our data indicate that the oxytocinergic system has a modulatory function on nociception.

Central administration of the endopeptidase 24.15 inhibitor cFP-AAF-pAB suggests dynorphin as the endogenous ligand underlying behavioral effects of milk in the fetal rat

Intraoral infusion of milk to the rat fetus promotes opioid activity that results in reduced responsiveness in a behavioral bioassay involving perioral cutaneous stimulation. Intracisternal administration of cFP-AAF-pAB, an inhibitor of endopeptidase 24.15, prolonged the opioid activity induced by milk infusion. Treatment with the selective kappa opioid antagonist nor-binaltorphimine blocked the effect of cFP-AAF-pAB on milk-induced opioid activity, but treatment with the mu antagonist CTOP or the delta antagonist naltrindole did not. These findings imply that milk may exert its effect on fetal behavior by increasing levels of dynorphin in the fetal central nervous system.

Levofloxacin, an optical isomer of ofloxacin, has attenuated epileptogenic activity in mice and inhibitory potency in GABA receptor binding

The combination of some new quinolone antibacterials with 4-biphenylacetic acid (BPAA) functionally inhibits the gamma-amino-butyric acid (GABA) receptors and thereby induces clonic convulsions. We examined the effects of ofloxacin and its optical isomers on this quinolone-induced neurotoxicity. Norfloxacin at 10(-5) M alone or at 10(-7) M in combination with BPAA (10(-4) M) inhibited [3H]muscimol binding to rat brain synaptic membranes. Ofloxacin and its optical isomers did not affect muscimol binding by themselves. While they slightly reduced muscimol binding at 10(-4) M in combination with BPAA, the inhibitory activity of the l-isomer levofloxacin (DR-3355) on muscimol binding was slightly, but significantly, weaker than that of the d-isomer DR-3354 and ofloxacin. Intracisternal injection of norfloxacin (5 micrograms), ofloxacin, levofloxacin or DR-3354 (50 micrograms each) induced clonic convulsions in mice. The incidence of these convulsions was enhanced by the combination with BPAA (50 micrograms). The epileptogenic activity of levofloxacin was also weaker than that of DR-3354 or ofloxacin when quinolones were given alone or in combination with BPAA. These results suggest that epileptogenic activity of quinolones is closely related to the inhibitory potency in GABA receptor binding and that levofloxacin may have lower neurotoxicity than ofloxacin and DR-3354.

The analgesic mechanism of processed Aconiti tuber: the involvement of descending inhibitory system

Tsumura-shuchi-bushi-matsu (TJ-3021) is a processed Aconiti tuber which has a potent antinociceptive action. The present study was undertaken to study the analgesic mechanism produced by TJ-3021. RCS (repeated cold stress) rats in hyperalgesia were markedly suppressed by oral administration of TJ-3021. Intrathecal and intraperitoneal administration of a selective alpha 2-adrenoreceptor antagonist, idazoxan (IDA), reduced significantly the analgesic effect of TJ-3021 in RCS rats. Methysergide (METH), a 5-HT receptor antagonist, demonstrated a similar effect, while intraperitoneal administration of opioid receptor antagonist, naloxone, did not produce the effect. Both oral and intracisternal administration of mesaconitine (MA) which is one of the main potent alkaloids contained in TJ-3021 produced analgesic effect in non-RCS rats.

Failure to transfer multiple sclerosis into severe combined immunodeficiency mice by mononuclear cells from CSF of patients

To confirm the reported transfer of multiple sclerosis (MS) by CSF cells, we injected CSF cells from six MS patients in the exacerbation stage into the cisterna magna of 18 severe combined immunodeficiency mice. No clinical neurologic abnormalities or light- or electron-microscopic pathologic changes were present in any transferred mice, and the reported results could not be reproduced.

Differing effects of vasopressin on regional cerebral blood flow of dogs following intracisternal vs. intra-arterial administration

We investigated the differential effect of the intracisternal and intraarterial administration of vasopressin on the regional cerebral blood flow (rCBF) in the parietal cortex of dogs. Regional CBF, velocity and blood volume were assayed by laser flowmetry. The intracisternal injection of 1 nmol vasopressin significantly increased the rCBF and velocity, without affecting blood volume. However, the intravertebral arterial injection of 1 nmol vasopressin significantly decreased the rCBF and velocity. This discrepancy can be explained by a difference in the affected vasculature; large blood vessels in the subarachnoid space vs. whole cerebral vascular system. The intracisternal and intraarterial injection of the nitric oxide inhibitor NG-monomethyl-L-arginine reduced the rCBF from the base line, and significantly suppressed the rCBF elevation induced by vasopressin. The effect of vasopressin may be considered as the summation of the increased flow from the dilated large vessels via the release of nitric oxide from the endothelium, and of the decreased flow from the contracted small vessels.

Naltrexone in vivo protects mu receptors from inactivation by beta-funaltrexamine, but not kappa receptors from inactivation by nor-binaltorphimine

The ability of the competitive opioid antagonist, naltrexone, to protect opioid receptors from inactivation by the nonequilibrium antagonists, beta-funaltrexamine (beta-FNA) and nor-binaltorphimine (nor-BNI), was examined in vivo. Male rats were injected SC with 10 mg/kg naltrexone or saline, 30 min before being injected intracisternally (IC) with water, 10 micrograms beta-FNA, or 1.0 or 10 micrograms nor-BNI. The rats were tested for analgesic responses to either U69,593 (nor-BNI groups) or morphine (beta-FNA groups), on a 50 degrees C hot plate, 24 h later. Morphine produced dose-related increases in the latency to paw lick in rats that received water (IC) (mean ED50 = 3.2 mg/kg). Little or no analgesia occurred after 1.0-30 mg/kg of morphine in animals that had received saline (SC) and 10 micrograms beta-FNA (IC) 24 h earlier. Pretreatment with 10 mg/kg naltrexone attenuated the antagonist effects of beta-FNA (morphine ED50 = 10.8 mg/kg). U69,593 also produced analgesia in animals that received water (IC) (ED50 = 0.97 mg/kg). This analgesia was dose-dependently blocked by nor-BNI for up to 7 days. Naltrexone did not inhibit the actions of nor-BNI. Thus, naltrexone prevented inactivation of mu receptors by beta-FNA but not inactivation of kappa receptors by nor-BNI, suggesting that antagonist interactions with mu receptors are different from those with kappa receptors.

[Traumatic primary brain stem injury and ambient cistern hematoma evaluated with magnetic resonance imaging]

Traumatic hemorrhage in the ambient cistern is thought to be an indirect indication of brain stem injury. In many cases such brain stem lesions cannot be clearly demonstrated by conventional CT scans. Magnetic resonance imaging (MRI) provides a more sophisticated display of the brain stem with improved contrast resolution of structures not appreciated on CT. We present four patients with traumatic ambient cistern hematoma on CT. They showed consciousness disturbance at the initial neurological examination and a Glasgow Coma Scale (GCS) of 7-10. All patients had hemothorax or clavicular fracture ipsilateral to the ambient cistern hematoma that suggested a severe mechanical force from the same direction. Axial, coronal and sagittal MRI scans were obtained with a super-conductive 1.5 T unit (Picker) within 6 days after trauma. Two standard pulse sequences were used; (1) Spin-echo (TR/TE = 500/20) or Inversion Recovery (TR/TI/TE = 3300/600/30) to obtain T1-weighted information and (2) Spin-echo (TR/TE = 2000/100) to obtain T2-weighted information. In case 1 (3-year-old girl) the hematoma which was thought to be located in the ambient cistern on CT was found to be present in the subpial region in the tegmentum on MRI. On T2 weighted image, a high signal intensity area was seen in the perifocal area. This area was demonstrated as a low density area on CT. This patient has remained in a persistent vegetative state 6 months after trauma. In case 3 (31-year-old man) CT demonstrated no abnormal findings in the brain stem. MRI demonstrated a high intensity area in the right cerebral peduncle and left tegmentum.(ABSTRACT TRUNCATED AT 250 WORDS)

Sympathoinhibitory action of rilmenidine in conscious sinoaortically denervated rats

The responses of mean arterial pressure (MAP), heart rate (HR), and renal sympathetic nerve activity (RSNA) to rilmenidine administration and changes in these responses after idazoxan or yohimbine pretreatment were investigated in conscious sinoaortically denervated rats. Intravenous (i.v.) injection of rilmenidine (300 and 600 micrograms/kg) dose-dependently reduced MAP (16 and 24%, respectively) and RSNA (31 and 56%, respectively), whereas bradycardia was similar at both doses of the drug. Intracisternal (i.c.) pretreatment with idazoxan (5 micrograms/kg), alpha 2-adrenoceptor antagonist with a high affinity to imidazoline receptors (IR) prevented rilmenidine-induced decreases in MAP but not in RSNA and HR. Rilmenidine (300 micrograms/kg i.c.) significantly decreased MAP by 24%, RSNA by 32%, and HR by 13%. Pretreatment with idazoxan (1 microgram/kg i.c.) significantly attenuated the hypotensive and sympathoinhibitory effects of rilmenidine, whereas i.c. pretreatment with equimolar to 10-fold higher doses of yohimbine, an alpha 2-antagonist that binds poorly with IR, did not. Both idazoxan and yohimbine failed to affect the rilmenidine-induced bradycardia, however. We concluded that (a) rilmenidine exhibits more marked hypotensive effect when injected i.c. than when injected i.v., (b) a part of the inhibitory effect of i.v.-injected rilmenidine on RSNA may be exerted through idazoxan-insensitive mechanisms which might be activated by peripheral action of the drug, and (c) the hypotensive action of rilmenidine relates more to the interaction with IR than with alpha 2-adrenoceptors.

Neural mechanism underlying basilar arterial constriction by intracisternal L-NNA in anesthetized dogs

Basilar arterial diameters were angiographically measured in anesthetized dogs in which systemic blood pressure and heart rate were also monitored. Injections of NG-nitro-L-arginine (L-NNA), a NO synthase inhibitor, into the cisterna magna produced a significant, persistent decrease in arterial diameter, the effect being reversed by intracisternal injections of L-arginine. The vasoconstrictor effect of L-NNA was diminished in dogs treated with hexamethonium. On the other hand, treatment with phentolamine in a dose sufficient to lower blood pressure to a level similar to that attained with hexamethonium did not inhibit, but rather potentiated, the effect of intracisternal L-NNA. Nicotine injected into the vertebral artery significantly dilated the basilar artery. The effect was abolished by treatment with L-NNA applied intracisternally, the inhibition being reversed by the addition of L-arginine. Systemic blood pressure and heart rate were not altered by intracisternally applied L-NNA and L-arginine. These findings support the hypothesis that basilar arterial constriction caused by intracisternal L-NNA is associated with a suppression of NO synthesis in nitroxidergic nerves innervating the cerebroarterial wall rather than an elimination of basal release of NO from the endothelium. Functional importance of nitroxidergic vasodilator innervation in cerebral arteries in vivo is thus clarified.

Effects of intracisternal monoamines on breathing movements in fetal sheep

The effects of intracisternal administration of tyramine on fetal breathing movements (FBM), electrocortical (ECoG) and nuchal muscle activities, and cerebrospinal fluid (CSF) monoamine concentrations have been studied in unanesthetized fetal sheep (124-140 days gestation) in utero. In 18 trials (8 fetuses) infusion of 50 or 100 micrograms/kg tyramine increased the incidence of FBM from 32.2 +/- 2.0 to 79.4 +/- 4.7%/h (P < 0.05) and increased mean breath amplitude from 6.4 +/- 0.4 to 11.8 +/- 1.6 mmHg (P < 0.05). FBM incidence during high-voltage ECoG activity increased from 3.3 +/- 0.6 to 22.5 +/- 3.6%/h (P < 0.05). Tyramine infusion (100 micrograms/kg) significantly increased (P < 0.05) the CSF concentrations of dopamine from 129.5 +/- 26.2 to 10,222.4 +/- 1,103.6 pg/ml, of norepinephrine from 74.7 +/- 11.0 to 2,238.6 +/- 143.5 pg/ml, and of serotonin from 1,824.5 +/- 340.7 to 3,888.7 +/- 1,335.2 pg/ml. Intracisternal injection of dopamine or norepinephrine (10-20 micrograms) caused the rapid onset of large-amplitude FBM, which often continued throughout high-voltage ECoG activity. In contrast, serotonin (20-40 micrograms) caused cessation of FBM and change of the ECoG from low- to high-voltage activity. These results indicate that neuronal release of catecholamines in the CNS has excitatory effects on FBM.

Effect of ACTH-(4-10) and gamma 2-MSH on blood pressure after intracerebroventricular and intracisternal administration

After intracerebroventricular (i.c.v.) administration of ACTH-(4-10) or gamma 2-MSH in doses of < or = 1,500 pmol, no changes were observed in mean arterial pressure (MAP) of conscious and urethane-anesthetized rats. When gamma 2-MSH was administered intracisternally (i.c.), a significant increase in MAP of approximately 15 mm Hg was observed after the two highest doses used (500 and 1,500 pmol) in conscious rats and also, though less pronounced, in urethane-anesthetized rats. Although the pressor effect of gamma 2-MSH after intravenous (i.v.) administration to conscious rats was maximal within 25 s and MAP had returned to preinjection values < or = 60 s, the pressor response after i.c. administration was slower in onset (maximal effect after 1-2 min) and of longer duration (return to preadministration values after 5 min). ACTH-(4-10) had a slight pressor effect after i.c. administration in doses of 1,500 and 2,500 pmol in conscious rats, but had no effect in urethane-anesthetized rats. These results indicate that sustained leakage of the peptides after i.c. administration, but not after i.c.v. administration, to the periphery is the causal factor of a modest pressor response. These results do not support the suggestion that the central nervous system (CNS) is the principal target of gamma-MSH-like peptides with respect to their pressor effect.

Role of imidazoline-preferring receptors in the genesis of epinephrine-induced arrhythmias in halothane-anesthetized dogs

BACKGROUND

Drugs with a central alpha 2-adrenergic action can increase the threshold for halothane-epinephrine-induced arrhythmias. Recently, imidazoline-preferring receptors were shown to play a significant role in the hypotensive effect of alpha 2-adrenergic agonists containing an imidazole ring in their structure. To address the question of whether the antiarrhythmic property of the alpha 2-adrenergic agonists was caused by activation of alpha 2-adrenoceptors or imidazoline-preferring receptors in the central nervous system, the effect of an imidazoline (atipamezole) and a nonimidazoline (L-659,066 and yohimbine) alpha 2-adrenergic antagonist were examined as etiologic factors in the genesis of halothane-epinephrine-induced arrhythmias in dogs.

METHODS

Adult mongrel dogs were anesthetized with halothane (1.3%) and monitored continuously for systemic arterial pressure and for premature ventricular contractions. The arrhythmogenic dose (AD) of epinephrine, defined as the smallest dose producing four or more premature ventricular contractions within a 15-s period, was determined in the presence of atipamezole (an imidazoline compound that acrosses the blood-brain barrier), L-659,066 (a nonimidazoline compound that does not penetrate the blood-brain barrier), and yohimbine (a nonimidazoline compound that passes the blood-brain barrier). These drugs were administered either intravenously or into the cisterna magna to assess the site of action for changes in responsiveness.

RESULTS

Intravenous atipamezole decreased the AD of epinephrine in the dose-dependent fashion. However, neither L-659,066 nor yohimbine, administered peripherally, decreased the AD of epinephrine. Central administration of atipamezole also decreased the AD of epinephrine, while L-659,066, even if administered centrally, did not affect the AD of epinephrine in the presence of halothane.

CONCLUSIONS

Because the imidazoline ring-containing alpha 2-adrenergic antagonist (atipamezole) potentiated the halothane-epinephrine-induced arrhythmias and the nonimidazole alpha 2-adrenergic antagonist (L-659,066 and yohimbine) did not, it is possible that the imidazoline-preferring, rather than the alpha 2-adrenergic, receptor is responsible for the antiarrhythmic property of alpha 2-adrenergic agonists.

Preventive therapy against delayed cerebral ischaemia after aneurysmal subarachnoid haemorrhage: trials of thromboxane A2 synthetase inhibitor and hyperdynamic therapy

The effects of thromboxane A2 synthetase inhibitor and hyperdynamic therapy on delayed cerebral ischaemia following aneurysmal subarachnoid haemorrhage were evaluated in a series of twenty eight patients, who underwent aneurysmal clipping with 72 hours after subarachnoid haemorrhage. Postoperatively, 13 patients were treated with thromboxane A2 synthetase inhibitor, Xanbon [sodium (E)-3-[p-(1H-imidazol-1-ylmethyl)phenyl]-2-propenoate]. Hyperdynamic therapy with dobutamine was given to the remaining 15 patients. Of the 13 patients treated with Xanbon, nine patients (69%) developed delayed cerebral ischaemia and cerebral infarcts occurred in eight patients (62%). On the other hand, of the 15 patients treated with hyperdynamic therapy, only three patients (20%) manifested delayed cerebral ischaemia and two patients (13%) developed cerebral infarcts. In the present study, the patients treated with hyperdynamic therapy met an expected incidence of ischaemic events after subarachnoid haemorrhage by today's standards, while those treated with thromboxane A2 synthetase inhibitor did not.

Action of endothelin-1 on vasomotor neurons in rat rostral ventrolateral medulla

Intracisternal administration of endothelin-1 (ET-1) elicits sympathetically mediated cardiovascular responses by acting on the ventral surface of the medulla oblongata (VSM) subjacent to the rostral ventrolateral medulla (RVLM). We examined, in urethane-anesthetized rats, whether intracisternal ET-1 affected activity of vasomotor neurons (VMNs) in the RVLM, by acting either directly on the VMNs or indirectly via the VSM. VMNs were identified electrophysiologically. Intracisternal administration of ET-1 altered activity of all the 13 VMNs tested. At a dose of 0.1 pmol, ET-1 invariably caused transient excitation in six VMNs examined, whereas at a dose of 1 pmol in separate experiments all the seven VMNs tested were inhibited with (n = 6) or without (n = 1) preceding excitation. Similarly, topical application of ET-1 (0.1-1 pmol) to the VSM caused inhibition with (n = 3) or without (n = 2) preceding excitation in all the five VMNs tested. Direct iontophoretic application of ET-1 to the VMNs caused excitation in four of seven VMNs examined but did not affect the other three neurons. These results support the view that intracisternally administered ET-1 alters activity of VMNs in the RVLM, by acting directly on neurons themselves and indirectly via the VSM.

BQ-123, a peptidic endothelin ETA receptor antagonist, prevents the early cerebral vasospasm following subarachnoid hemorrhage after intracisternal but not intravenous injection

The aim of this study was to evaluate the role of endothelin and endothelin ETA receptor in the early cerebral vasoconstriction following subarachnoid hemorrhage (SAH) in the rat. SAH induced by injection of autologous blood in the cisterna magna reduced by 22 to 38% cerebral blood flow (CBF) measured with radioactive microspheres at 30, 60 and 120 min after SAH. The cyclic pentapeptide BQ-123, a selective antagonist of the ETA receptor, injected intravenously (3 mg/kg) had no effect on this decrease in CBF. However, intracisternal BQ-123 (10 nmol) completely prevented the decrease in CBF at 60 and 120 min after SAH. These results suggest that BQ-123 does not cross the blood-brain barrier, but demonstrate that endothelin acting on ETA receptor plays a role in the pathogenesis of cerebral vasoconstriction in this rat model of SAH.

Effects of intracisternal vs. intrahypothalamic 5,7-DHT on feeding elicited by hypothalamic infusion of NE

A variety of evidence has led to suggestions that brain serotonin (5-HT) and norepinephrine (NE) interact within the medial hypothalamus to control food intake. To test the possibility that chronic decrements in 5-HT might enhance NE-induced feeding, adult male rats were prepared with permanently indwelling cannulae aimed at the paraventricular nucleus (PVN), then received either intracisternal (IC) or PVN injections of the 5-HT neurotoxin, 5,7-dihydroxytryptamine (5,7-DHT) vs. its vehicle, 1% ascorbic acid. Over a 4-week period, IC-5,7-DHT rats showed no signs of enhanced daily feeding or drinking. However, in 40-min intake tests, feeding but not drinking was enhanced by injecting 20 nmol NE into the PVN commencing 2 weeks after neurotoxin treatment. Terminal monoamine assays confirmed that IC-5,7-DHT produced large (80-90%) depletions of brain regional 5-HT. A functional index of 5-HT terminal damage was also implied by the impaired short-term feeding responses IC-5,7-DHT rats showed to the systemic administration of the 5-HT1A agonist, 8-hydroxy-2-(di-n-propylamino) tetralin (8-OH-DPAT) when tested between 3 and 4 weeks after IC treatment. Over a comparable 4-week period, PVN-5,7-DHT rats also showed no tendencies to overeat or overdrink on a daily basis. However, in contrast to IC-5,7-DHT rats, they also showed no differences in their feeding or drinking responses to NE injections into the PVN. This was so despite reliable depletions of 5-HT in the hypothalamus (-28%) and hippocampus (-71%). These results support earlier work showing that neither widespread nor localized hypothalamic damage to brain 5-HT neurons produce chronic overeating. However, the data suggest that phasic enhancements of PVN NE activity may trigger enhanced feeding when there is widespread damage to brain 5-HT neurons, although the PVN does not appear to be the brain site mediating this effect.