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PubMedDate not supplied

Inhibition of nitric oxide synthase in the hypothalamus blocks the increase in plasma prolactin induced by intraventricular injection of interleukin-1 alpha in the rat.

Injection of interleukin-1 (IL-1) into the third cerebral ventricle (3V) of conscious rats increases plasma prolactin (PRL) concentration. Nitric oxide (NO) is involved in control of corticotropin-releasing factor (CRF) and luteinizing hormone-releasing hormone (LHRH) release. Consequently, we evaluated its role in the PRL-releasing action of IL-1. In the present experiment, NG-mono-methyl-L-arginine (NMMA) (1 mg in 5 microliters of 0.9% NaCl (saline)], an inhibitor of NO synthase, or 5 microliter of saline was microinjected into the 3V of conscious, castrate male rats and blood samples were removed from jugular catheters just prior to and at 10-min intervals after injection. A second injection of NMMA or saline was given 60 min after the first. Five minutes after the injection of NMMA or saline, IL-1 alpha (0.6 pmol in 2 microliter saline), or an equal volume of saline, was injected into the 3V. Plasma PRL concentrations were increased within 10-20 min after injection of IL-1 alpha and a second pulse of PRL usually occurred at 60-70 min following its injection. The maximal increase in plasma PRL from the initial value in the animals injected with IL-1 alpha was highly significant, whereas there was no significant increase in the animals injected with NMMA plus IL-1 alpha or in the animals injected with saline or NMMA. The area under the plasma PRL curve was significantly elevated in the animals injected with IL-1 alpha above that of rats injected with NMMA plus IL-1 alpha during the first hour after injection.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Effect of intraventricular injection of 1-methyl-4-phenylpyridinium: protection by acetyl-L-carnitine.

1-methyl-4-phenylpyridinium (MPP+) is the bioactivated product of 1-methyl-4-phenyl- 1, 2, 3, 6-tetrahydropyridine (MPTP). The neurotoxic action of MPP+ injected intracerebroventricularly (ICV) in the rat has been studied, using dopaminergic systems in the substantia nigra, striatum, olfactory bulb, median eminence and hypophysis. The following results were obtained: (1) Rats with ICV administration of 1 microliter MPP+ solution (62.5 micrograms of MPP+ rat) showed 50% mortality; (2) The ICV administration of MPP+ produced a decrease in dopamine (DA) concentration in different areas of rat CNS studied: striatum (83%), hypophysis (95%) and median eminence (70%). However, olfactory bulb and substantia nigra were not affected; (3) MPP+ by ICV administration produced neurotoxic effect on the dopaminergic system. We also studied the possible protective action of acetyl-L-carnitine (ALC) against the neurotoxic action of MPP+. Rats were intraperitoneally injected daily for 8 days with 100 mg kg-1 of ALC and 3 days from the beginning of the MPP+ treatment; (4) We found that the ALC treatment significantly protected against mortality produced by the ICV injection of MPP+. Rats treated with ALC showed no mortality; (5) We did not find a protective effect on the dopaminergic system studying either catecholamine concentration or measuring tyrosine hydroxylase, neurofilament or glial fibrillary acid protein; (6) The results suggest that the ALC protective action could be related to energy metabolism.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1977

Suppression of feeding and drinking activity in rats following intraventricular injection of thyrotropin releasing hormone (TRH).

Since both TRH and somatostatin (SRIF) are localized to the ventromedial hypothalamic nucleus, a region known to be involved in control of food intake, the possibility that these peptides might alter food intake was evaluated. The peptides were dissolved in 0.9% NaCl and injected into the 3d ventricle in a volume of 2 micron1 in animals bearing 3d ventricular cannulae. Food and water had been removed from the cages the night before and the intake was measured at 1 and 6 h after injection. Control injections of 0.15M NaCl or glutathione (3 nmoles) had no effect on food or water intake. At a dose of 3 nmoles, LHRH, SRIF, and TRH suppressed water intake alh. Lowering the dose of LHRH and SRIF to 0.6 nmoles led to loss of this inhibition but the suppressive effect of TRH, which was more pronounced at the higher dose than that of the other two peptides, persisted. Lowering the dose of TRH to 0.3 nmoles led to loss of the inhibitory effect. The dose of 3 nmoles of LHRH did not suppress food intake but this dose of both SRIF and TRH had a significant suppressive effect on food intake at 1 h. There was no suppressive action of a lower dose of 0.6 nmoles of SRIF, but TRH was still effective to suppress food intake at this dose. A dose of 0.3 nmoles of TRH had no effect on food intake. It is suggested that TRH, and possibly SRIF may play a physiological role in control of food intake, perhaps by altering the neural activity within the ventromedial nucleus.

Animals↗
PubMed1978

Angiotensin II concentration in cerebrospinal fluid after intraventricular injection of angiotensinogen or renin.

To determine if the brain enzyme which has renin-like activity in vitro can form angiotensin in vivo, angiotensin II concentration in cerebrospinal fluid (CSF) was measured before and at various intervals after injection of partially purified renin substrate (angiotensinogen) into the third cerebral ventricle of anesthetized dogs. The injection increased CSF angiotensinogen concentration 3-fold, but despite this, CSF angiotensin II concentration, which was undetectable (less than 6.25 fmol/ml) before injection, did not change. Arterial blood pressure was also unchanged after the injection. In contrast, both CSF angiotensin II concentration and arterial pressure increased after an inventricular injection of renin. These results demonstrate that angiotensin II is formed centrally after administration of exogenous renin but not after injection of angiotensinogen. The results thus fail to demonstrate renin activity in the brain in vivo.

Angiotensin II↗
PubMed1976

[Changes in the substantia nigal self-stimulation behavior caused by intraventricular injection of norepinephrine, dopamine and GABA].

A bipolar electrode was stereotaxically implanted in the substantia nigra of male albino Wistar-Imamichi rats. Effects of l-norepinephrine (NE), dopamine (DA) and gamma-aminobutyric acid (GABA), injected into the lateral ventricle, on the substantia nigral self-stimulation (SS) behavior, and the effect of alpha- and beta-adrenergic receptor antagonists on the facilitation induced by NE were investigated. NE but not DA facilitated the SS behavior and GABA showed no constant effects on the behavior. Facilitation by NE of SS behavior was inhibited by phentolamine, but not by propranolol. These results suggest that the noradrenergic system in the brain may play a more significant role in the positive reinforcement of the substantia nigral SS behavior than does the dopaminergic or GABA-ergic system, and that the action of NE may be facilitated through alpha-receptors rather than through beta-receptors.

Aminobutyrates↗
PubMed1989

Effect of intraventricular injection of muscimol on appetite in rats kept at high and temperate ambient temperatures.

The central mechanism controlling food intake in response to the change in environmental temperature has been little examined. The GABA agonist, muscimol, was injected into the lateral ventricle of rats which were acclimated to temperate (26 degrees C) and hot (33 degrees C) environments. Muscimol obviously stimulated the feeding behavior of rats in both environments. However, when muscimol was administered at doses of 100 and 250 ng, the food intake at 26 degrees C was greater than that at 33 degrees C. In addition, the stimulating effect of muscimol (250 ng) on food intake at 26 degrees C lasted longer than that at 33 degrees C. These findings suggested that there might be a difference in muscimol metabolism at the two temperatures.

Acclimatization↗
PubMed1991

Effects of intraventricular injection of delta receptor antagonist ICI 154, 129 on the secretion of luteinizing hormone and prolactin in the proestrous rat.

In order to ascertain the role of delta receptors in the control of gonadotropin secretion, a preferential delta receptor antagonist ICI 143,129 was microinjected into the third ventricle through chronically implanted cannulae and the effects on the serum concentration of luteinizing hormone (LH) and prolactin (PRL) were determined in female rats in proestrus. When the injection was given at 1030 h, ICI 154,129 (50 micrograms) exerted no significant effects on either LH or PRL. However, in the rat given a microinjection of ICI 154,129 at 1300 h, an afternoon rise in LH occurred in advance and was of greater magnitude, with the peak time more than 1 h earlier and the peak amplitude approximately 100% greater than that in the control rat, respectively. The injection also suppressed the PRL rise during the plateau phase. The results indicate that delta receptors are involved in the mediation of the inhibitory influence of endogenous opioids on the surge of LH in proestrus, and that delta receptors mediate the facilitatory influence of opioids on the PRL surge during the plateau phase.

Analysis of Variance↗
PubMed1978

Changes in serum TSH level after intraventricular injection of various neuromediators in rats.

The influence of various neuromediators on pituitary TSH secretion in rats has been investigated. Noradrenaline 50 microgram/rat, dopamine 50 microgram/rat, serotonine-creatinine-sulphate 100 micogram/rat, gamma-aminobutyric acid 100 microgram/rat, pilocarpine 1 mg/rat, histamine 100 microgram/rat were administered into the lateral ventricle of the brain. All agents were dissolved in Parker's fluid. Two control groups of animals were given Parker's fluid and subjected to surgical manipulations, respectively. Plasma TSH level was estimated after 30 min by means of radioimmunoassay. The increase in the TSH level was observed after the injection of serotonine and noradrenaline (4.0 and 3.1 ng/ml, respectively) as compared with control group (0.7 ng/ml).

Aminohippuric Acids↗
PubMed1981

Effects of intraventricular injections of Ca2+ and(or) Mg2+ on eating behavior, water intake and cardiac rhythm in sheep.

Feeding behavior, water intake and cardiac rhythm were measured following injections of Ca2+ and(or) Mg2+ into the lateral ventricles of sheep. Injections of 20 mumoles of either Ca2+ or Mg2+ elicited an eating response approximately three to four times greater than normal. The effect of Ca2+, however, appeared to be more powerful than that of equimolar doses of Mg2+. When both ions were injected in an equimolar mixture (10 mumoles of each), they did not antagonize each other, but instead elicited an eating response that was additive and equal to that elicited by 20 mumoles of Ca2+. Water intake varied markedly and was not related to the experimental treatments. Cardiac rate was decreased by the injections of 20 mumoles of Ca2+, with the T-P interval of the electrocardiogram affected most. The other experimental treatments did not affect cardiac rate, although the intervals between the waves QRS, T and P of the electrocardiogram were slightly modified. It is concluded that lateral ventricular injections of Ca2+ and Mg2+ can affect the excitability of neurons controlling feeding behavior without necessarily affecting other autonomic centers in sheep, unless the ions reach the vicinity of the fourth ventricle at relatively high concentrations.

Animals↗