Ic Injection Research Articles

121 INTRACISTERNALLY (ic) GIVEN E.COLI O 111 B 4 ENDOTOXIN (LPS) OPENS THE BLOOD-BRAIN BARRIER (BBB) FOR NA-FLUORESCEIN (NaF) IN NEW BORN PIGLETS

Despite decades of investigating the BBB, there remains a distinct paucity of data regarding its response to infections. We have studied the pial-arachnoid microvasculature in vivo in newborn piglets through an open cranial window using fluorescence photomacroscope giving 20 μg (n=6) -Group 1- and 200 μg (n=6) -Group 2- LPS ic. Control animals (n=6) -Group 3- were given mock cerebrospinal fluid (CSF). CSF LPS concentration was determined using chromogenic limulus amcbocyte lysate assay. NaF (MW=376) given intravenously was used as a BBB permeability marker and brain NaF uptake (BNU) was measured by a spectrofluorometer. In Group 3 (the BBB remained light through the experimental period (4 hours), there were neither fluorescein extravasation nor significant BNU. In Group 1 the BBB was opened (extensive fluorescein leakage) 70.5±10.5 min after the ic LPS injection, and CSF LPS levels was significantly elevated (0.70±0.10 EU/ml) at that time compared to the value measured at the start of the experiment (0.14±0.04 EU/ml; p<0.05). There was an elevation in BNU (3.0±0.7 μg NaFxmg−1 protein/μg NaFxμl−1 serum) at the time of sacrifice (4 hours). In Group 2 the BBB was opened significantly earlier (55.2±4.1 min), and CSF LPS content (1.18±0.10 EU/ml) and BNU (5.9±0.9 μg NaFxmg−1 protein/μg NaFxμl−1 serum) were also highly elevated compared to the Group 1 (p<0.05 in each parameter). It is concluded that ic given LPS, as a model of neonatal purulent meningitis, results in a dose dependent opening of the BBB for NaF, and in marked changes in the extracellular fluid space of the brain. (All values are mean±SD.)

Magnetic resonance imaging study of the rat cerebral ventricular system utilizing intracerebrally administered contrast agents

Magnetic resonance imaging (MRI) was employed to study the rat brain in conjunction with intracerebral (ic) injection of three contrast agents: GdHAM, GdDPTA, and MnCl2. The results demonstrate several advantages of ic administration of MRI contrast agents over the other routes of injection in examining CSF dynamics and brain ventricular structure. Apparent affinity of the luminal ventricular wall of the brain for positively charged GdHAM and Mn2+ ions is observed, presumably reflecting the presence of negatively charged wall components. Respiratory distress caused by (intravenous) injection of GdHAM was found to be minimized in the case of ic injections. Time-dependent changes in observed contrast indicate that diffusive processes rather than flow of CSF play a dominant role in distributing the contrast agents. Possible applications of this approach in brain research are discussed.

Gastric cytoprotection by intracisternal interleukin-1β in the rat

The effects of intracisternal (ic) injection of recombinant interleukin-1β(IL-1) on absolute ethanol-induced gastric necrotic lesions were studied in conscious rats. IL-1 given ic inhibited ethanol-induced gastric lesions. The cytoprotective effect was dose dependent (ED 175 ng/rat), long lasting with a maximal action when given 1–3 h prior to ethanol, blocked by ic injection of a IL-1 receptor antagonist protein (IRAP), and by intraperitoneal injection of indomethacin. IL-1, injected ic, was detected in the peripheral blood. However, IL-1 serum levels were lower after IL-1 injection ic than after ip at a dose giving equal gastric protection. These data show that ic IL-1 induces long lasting gastric protection mediated by interaction with IL-1 receptors and prostaglandin pathways at central and/or peripheral sites that remain to be localized.

Central action of recombinant interleukin-1 to inhibit acid secretion in rats

The influence of recombinant human interleukins-1β and -1α and rat interleukin-1β on gastric acid secretion was investigated in awake rats with pylorus ligation. IC injection of either human interleukin-1β, human interleukin-1α, or rat interleukin-1β induced a dose-dependent inhibition of gastric acid output. At IC doses < 100 ng, human interleukin-1β was more effective than the other forms or sources of interleukin-1, whereas at higher doses (100–500 ng), human interleukins-1β and -1α and rat interleukin-1β were equipotent. The inhibitory effect was observed 30 minutes after interleukin-1 injection and maintained throughout the 6-hour experimental period. IC injection of interleukin-1β inhibited vagally stimulated gastric acid secretion induced by IC injection of the stable thyrotropin-releasing hormone analogue RX 77368. Indomethacin (1, 5, and 10 mg/ kg, IP, − 30 minutes) induced a dose-related prevention of the inhibitory effect of IC interleukin-1β. IC injection of the corticotropin-releasing factor antagonist α-CRF9-41, bilateral adrenalectomy, and noradrenergic blockade with bretylium did not influence the antisecretory effect of interleukin-1. Polypeptide action was not related to changes in circulating gastrin levels. Human interleukin-1β injected IV also inhibited gastric acid secretion, but the peripheral dose required to induce a significant effect was 103-fold higher than when given centrally. These results show that IC interleukin-1β acts centrally to induce a long-lasting inhibition of gastric acid secretion, and this effect requires the integrity of prostaglandin pathways. These data suggest a possible interaction between the immune and gastrointestinal systems.

Effects of beta-endorphin on DNA synthesis in brain regions of preweanling rats

Recent studies of whole brain in rat pups have shown a marked decrease in DNA synthesis following intracisternal (i.c.) administration of beta-endorphin (BE). This investigation examines DNA synthesis in the cerebral cortex and cerebellum to determine whether the effect shows regional selectivity. Two- to twenty-day-old rats were given a single ic injection of BE, and DNA synthesis was assessed 1 h later. In the cerebral cortex, a region that undergoes major phases of cell multiplication in the immediate pre- and postnatal periods, BE significantly decreased DNA synthesis in 2-day-old rats, and a maximal inhibition was obtained by 4 days of age. In contrast, the cerebellum, a region that grows predominantly after birth, showed less sensitivity to BE during the early postnatal days, and a maximal effect was not attained until 10 days of age. While at 15 days of age the inhibition began to diminish in the cortex, a maximal effect was still seen in the cerebellum. Naloxone prevented the response in both brain regions, indicating the participation of opioid receptors. These results indicate that CNS BE is apparently able to alter DNA synthesis throughout the brain, with the greatest sensitivity occurring in those regions with highest mitotic rates at the time of exposure to BE.

Role of central histaminergic mechanism in behavioural depression (swimming despair) in mice

The role of the central histaminergic system in depression was studied by using swimming despair test in mice - a behavioural model of depression. In this test, immobility of mice reflects a state of depression. Intracerebral (ic) injection of histamine (50–200 μg) increased significantly the immobility. The H 1-receptor blocker mepyramine (2.5–20 mg/kg ip) had no effect while H 2-receptor blocker cimetidine (100–200 μg ic) caused a significant decrease in immobility. The histamine induced facilitation was blocked completely by cimetidine and antidepressant drugs-imipramine and desipramine, but remained unaffected in mice pretreated with mepyramine or atropine. The H 2agonist impromidine (20–40 μg ic) also enhanced significantly, the immobility which was blocked by cimetidine and antidepressant drugs. It has been concluded that central H 2-receptors facilitate depression and antidepressant drugs block central H 2-receptors.

Motor performance effects of propylene glycol dinitrate in the rat.

Propylene glycol dinitrate (PGDN), a major constituent of a liquid torpedo propellant, produces incoordination and impairment of balance in humans. This study was conducted to evaluate the rat as a model for PGDN-induced motor performance decrement, and to determine if direct application of PGDN onto neural tissue is a useful alternative to other routes of exposure. PGDN was injected onto the cisterna magna (ic) of adult Sprague-Dawley rats trained on the accelerod, a test of motor performance. Three groups of 13-14 male rats each received a single dose of either 5 or 10 microliters PGDN or 25 microliters sterile saline (control) while anesthetized with halothane. Accelerod performance was measured 12 min after ic injection, then hourly for 6 h, and at 24 h. Injections were evaluated using a five-stage screening criterion to eliminate grossly traumatized subjects, to verify the accuracy of the injection, and to determine the extent of mechanical damage. Eighteen out of 41 subjects passed the five-stage screen. A significant decrease in performance occurred during the first 2 h following injection of 10 microliters PGDN compared to the control and the 5-microliters groups. N significant differences were seen between the 5-microliter and control groups. These data confirm previous findings of PGDN-induced changes in human motor performance, suggesting that the rat may be a useful model for further PGDN neurobehavioral assessment. The data also indicate that ic injection may be an effective alternative to other routes of exposure for materials with appropriate chemical and biological properties if an evaluation screen is used.

Thyrotropin-releasing hormone (TRH) acts centrally to stimulate gastric contractility in rats

Changes in gastric contractility induced by intracisternal (ic) injection of thyrotropin-releasing hormone (TRH) or a stable TRH analog, RX77368 [p-Glu-His-(3,3′-dimethyl)-Pro NH2] were investigated in 24 h fasted-conscious rats. Gastric contractility was monitored using chronically implanted extraluminal force transducers sutured to the corpus. Response elicited by a standard meal was used as a physiologic standard. Intracisternal injection of TRH (1ug) or RX77368 (100 ng), unlike saline, stimulated high amplitude gastric contractions. The stimulation of gastric contractions induced by ic RX77368 was dose dependent (3–100 ng), rapid in onset, long lasting and not mimicked by the intravenous route of administration. Atropine (0.1 mg/kg) partially antagonized and vagotomy totally blocked the RX77368 (100 ng, ic)-induced stimulation of gastric contractility. These results demonstrated that TRH or RX77368 acts within the brain to elicit potent contractions of the stomach; TRH action appears vagally mediated probably through cholinergic mechanism.

Cytoprotective effect of centrally administered corticotropin-releasing factor on stress-induced gastric mucosal lesions

The effect of intracisternal (ic) injection of ovine corticotropin-releasing factor (CRF) on the development of gastric mucosal lesions induced by cold-plus-restraint stress was studied in rats. Adult male Wistar rats were fasted for 24h. Following is injection of CRF or saline, they were restrained in wire mesh and placed supine in a cold room at 4°C for 3h. After the 3-h stress, rats were killed by decapitation. Gastric mucosa was exposed and mucosal lesions were assessed. This regimen consistently produced mucosal lesions in control rats. Ic injection of 15 μg CRF significantly inhibited the development of gastric mucosal lesions, while the effect was not reproduced by intraperitoneal injection of 45μg CRF. Ic injection of 5μg somatostatin-28 (SS-28) alone did not influence the development of gastric mucosal lesions in this model. When SS-28 was coadministered with CRF centrally, the cytoprotective effect of CRF in this model was completely abolished. The development of gastric mucosal lesions following the stress was prevented by the prior administration of chlorisondamine, a ganglion blocker or atropine, an antagonist of muscarinic cholinergic receptor, but it was not affected by the injection of phenoxybenzamine, an α-adrenergic blocker. When cold-plus-restraint rats were pretreated with indomethacin, an inhibitor of prostaglandin synthesis, the cytoprotective effect of centrally administered CRF was abolished.The results show that centrally administered CRF exerted a cytoprotective effect on stress-induced gastric mucosal lesions and the effect was counteracted by somatostatin-28. The action of CRF appears to be mediated centrally by inhibiting the activity of muscarinic cholinergic fibers, while locally, it requires intact prostaglandin synthesis.

Stimulation of ornithine decarboxylase activity by insulin in developing rat brain.

Insulin administered ip or intracisternally (ic) increased the activity of ornithine decarboxylase (ODC) in whole brains and brain parts of neonatal rats. Maximal stimulation of activity occurred 4-5 h after ip administration. At the highest doses, insulin stimulated ODC activity by up to 5- and 8-fold after ip and ic injection, respectively. The same amount of insulin given ic caused greater increases in activity than when given ip. Insulin stimulated ODC activity in 2-day-old and in 17- to 60-day-old rats but not in 5- or 9-day old neonates or 80-day-old adults. When insulin-induced hypoglycemia was prevented by giving dextrose, the stimulation of ODC activity was approximately the same as that in animals receiving insulin without dextrose. This indicates that insulin-induced stimulation of brain ODC activity was not caused by insulin-induced hypoglycemia or physiological responses to hypoglycemia. Since ODC is considered an indicator of growth stimulation, these results suggest that insulin or insulin-like peptides have a role in the regulation of brain development.

Effects of γ-Aminobutyric Acid and Histamine on Prolactin Secretion in the Rat

Histamine releases prolactin (PRL) in estrogen-progesterone primed male rats after both iv and intracisternal (ic) injection, but does not affect in vitro PRL secretion. This stimulatory effect is reversed by the alpha-adrenergic antagonist phenoxybenzamine and the histamine antagonist diphenhydramine, gamma-Amino butyric acid (GABA), which has little in vivo effect of its own, interferes with the activity of histamine and a variety of other stimulators of PRL secretion. These results suggest the involvement of the naturally-occurring substances histamine and GABA in the central regulation of PRL secretion.

The site of the suppressive action of dexamethasone on pituitary-adrenal activity.

Administration of 3H-dexamethasone with carrier to rats either into the third brain ventricle (ic) in doses ranging from 0.01 to 10 Wg, or intravenously in a dose of 10 μg was used to explore the site of the suppressive action of this steroid on pituitary-adrenal activity. Almost all of the radioactivity in the brain was shown to be unmodified dexamethasone. Following iv injection the uptake and disappearance patterns of dexamethasone in the brain were clearly distinct from that of the other tissues. Regional differences in concentration and uptake o:f dexamethasone could however be observed within the brain. In limbic and mesencephalic structures a rise in concentration was found up to 4 hr, yielding a maximum of approximately 0.025% of the injected dose per gram tissue. Four hr following ic injection, the dexamethasone concentration in the hypothalamus appeared to be much higher than after iv injection. This higher concentration was not associated with a proportionally greater suppression of the pituita...

Intracerebral passage of sarcoma 180 in mice and hamsters.

SummaryMouse sarcoma 180 has been through a total of more than 25 IC passages in suckling and adult mice. Sarcomatous brain suspensions also produced sarcomas in adult mice by subcutaneous route. The IC route in suckling mice was about 1,000 times as effective as subcutaneous route in adult mice. After serial IC passages in suckling mice the sarcoma was adapted to suckling hamsters by IC injection and to date more than 12 serial passages have been carried out in this animal. A strain of sarcoma 180 cells which has undergone more than 25 TC passages produced sarcomas regularly in adult mice after subcutaneous injection and required about 500,000 cells to give 100% “takes.” However, when inoculated IC into suckling mice these cells seemed less neurotropic than mouse (IC) passage sarcoma cells.