“Occult” hydrocephalus in children

The authors describe 32 children between 2 and 15 years of age who had hydrocephalus that was only clinically manifest late in life. The clinical picture of these children did not suggest an obvious increase in intracranial pressure; instead, the presenting signs were rather nonspecific and included macrocrania, mild psychomotor retardation, unsteady gait, increased muscle tone and deep tendon reflexes in the lower limbs, impaired ocular movement, epilepsy, and endocrine dysfunction. Their histories suggest the possible causes of the ventricular dilation in about one third of the cases were: perinatal hemorrhage, leptomeningitis, neurofibromatosis, and untreated aneurysm of the great vein of Galen. In 20 patients, however, no positive anamnestic findings were reported. CT scan revealed triventricular dilation in more than half of the cases; tetraventricular dilation was present in 6 patients, and biventricular dilation in the remaining subjects. All children underwent CSF shunting, which resulted in complete recovery in all but 2 cases. The most frequently recorded surgical complication was postoperative subdural effusion (7 subjects), which required surgical treatment in only 2 cases.Presented at the 15th Annual Scientific Meeting of the International Society for Pediatric Neurosurgery, New York, 1987     

Localization and Quantitative Autoradiography of Glutamatergic Ligand Binding Sites in Chick Brain

The anatomical localization of glutamate receptor subtype-selective ligand binding sites was investigated in 1-day-old chick brain using quantitative autoradiography. Under the conditions used, the regional distributions of [3H]glutamate, [3H]AMPA (a selective quisqualate receptor ligand) and [3H]kainate binding sites are manifestly different. [3H]l-glutamate binding is densely localized in the telencephalon, particularly in the neostriatum (2.8 pmol/mg protein). In addition, [3H]l-glutamate labels the thalamus, the nucleus mesencephalicus lateralis pars dorsalis, the superficial layers of the optic tectum and the molecular layer of the cerebellum. [3H]AMPA binding sites are most densely localized in the hippocampus (0.90 pmol/mg protein), with an otherwise relatively uniform distribution of binding within the telencephalon. [3H]AMPA also labels the striatum griseum et fibrosum superficiale of the optic tectum and the molecular layer of the cerebellum. [3H]Kainate binding sites are extremely densely packed in the molecular layer of the cerebellum (10 pmol/mg protein). Other regions of [3H]kainate binding include the hyperstriatum and the thalamus. The binding of the NMDA receptor channel blocker [3H]MK-801 is increased in the presence of 1 mM l-glutamate. [3H]MK-801 binding is generally widespread in the telencephalon but is notably absent from the ectostriatum. No evidence of [3H]MK-801 binding sites was detected in the cerebellum, even in the presence of 1 mM l-glutamate. The relatively high densities and the well-defined localizations of the glutamate receptor subtype binding sites suggest that chick brain provides a useful system for the further study of excitatory amino acid receptors.     

Autonomic control of acid phosphatase exocrine secretion by the rat prostate

Summary In vivo prostatic secretion was collected from retired breeder Sprague Dawley rats using a method for isolated perfusion of the rat prostatic urethra. Enzymatic acid phosphatase determination was performed on the collected effluent. Control acid phosphatase secretion was 24.2±2.7 nm over 30 minutes. Intravenous phenylephrine 5 mg/kg stimulated a 10 fold increase in acid phosphatase secretion. The secretion seen with phenylephrine was dose dependent and could be blocked with prazosin, but not yohimbine, atropine, or propranolol. Intravenous -adrenergic agonist isoproterenol caused no increase in the secretion of rat prostatic acid phosphatese. Intravenous administration of the cholinergic agonist pilocarpine also resulted in a dose dependent rise in acid phosphatase secretion. The stimulation seen could be blocked by atropine but not phentolamine or propranolol. The stimulation of acid phosphatase secretion seen with ₁ adrenergic or cholinergic agonists was not additive. Intravenous vasoactive intestinal peptide did not stimulate acid phosphatase secretion nor did it augment the secretion induced by ₁ adrenergic or cholinergic agonists. Release of acid phosphatase into rat prostatic exocrine secretion is under both ₁ adrenergic and cholinergic control.Supported by the US Veterans Administration     

Down-regulation of 3H-lofentanil binding to opiate receptors in different cultured neuronal cells

Summary There was stereospecific binding of ³H-lofentanil (K _D value = 1.53 nM) to membranes of neuroblastoma-glioma NG 108-15 cells which are known to bear high affinity binding sites for enkephalin derivatives (-opiate receptor subtype). There was no high affinity specific binding of the -opiate specific ligand ³H-sufentanil. The specific binding of ³H-lofentanil to -opiate receptor subtype was down-regulated (decrease in B _max value without change in the K _D value) after prolonged incubation of the cells in the presence of leu- and met- enkephalin (0.1 M). There was no down-regulation of the opiate receptors (³H-lofentanil and ³H-d-ala-d-leu-enkephalin specific binding) after incubation of NG 108-15 cells with drugs from the fentanyl series (alfentanil or sufentanil).In cultured neurones from rat forebrain (15 day old embryos), the ³H-lofentanil binding was specific with high affinity (K _D: 0.048 nM) and a slow dissociation rate similar to that in adult rat cortex. Drugs of the fentanyl series (4-anilino-piperidines) were potent displacers whereas agonists of the - (enkephalin derivatives), (phencyclidine, haloperidol, 3-hydroxyphenyl-propylpiperidine) or K- (U 50488) opiate sites had a low affinity (K _i > 0.5 M) for ³H-lofentanil specific binding sites. Since there was also specific binding of ³H-sufentanil, the opiate receptors in cultured neurones seem to be mainly of the -subtype and this is consistent with the ontogeny of opiate receptors subtypes. These receptors were down-regulated after incubation in the presence of etorphine, sufentanil and alfentanil but not enkephalin derivatives.These results strongly suggest specific binding of ³H-sufentanil and ³H-lofentanil mainly to the so-called -opiate receptors in cultured neurones and a specific binding of ³H-lofentanil to lower affinity -opiate receptors in neuroblastoma-glioma cells. The down-regulation of the -opiate binding sites in cultured neurones and that of the -site in neuroblastoma × glioma hybrid cells were dose-and temperature-dependent, induced by the corresponding high affinity agonists and prevented by naloxone. Morphine did not induce down-regulation of or receptor sites, possibly because of a partial antagonist effect on both receptor subtypes. Send offprint requests to J. M. Maloteaux at the above address     

The gastrointestinal prokinetic benzamide derivatives are agonists at the non-classical 5-HT receptor (5-HT4) positively coupled to adenylate cyclase in neurons

Summary We have previously shown that a non-classical 5-hydroxytryptamine (5-HT₄) receptor mediates the stimulation of adenylate cyclase activity in mouse embryo colliculi neurons in primary culture. The pharmacological characteristics of this receptor exclude the possibility that it belongs to the known 5-HT₁, 5-HT₂ or 5-HT₃ receptor types. Here we report that this 5-HT receptor can be stimulated by 4-amino-5-chloro-2-methoxy substituted benzamide derivatives. All these compounds have been reported to be potent stimulants of gastrointestinal motility and some of them are 5-HT₃ receptor antagonists. The rank order of potency of these substituted benzamide derivatives in stimulating cAMP formation was: cisapride > BRL 24924 > 5-HT > zacopride > BRL 20627 > metoclopramide. The non-additivity of benzamide and 5-HT activities suggests that 5-HT and the substituted benzamide derivatives act on the same receptor. Only ICS 205930, a recognized 5-HT₃ receptor antagonist, competitively antagonized the stimulatory effect of cisapride, zacopride and BRL 24924. However, its pK _i (6–6.3) for this new receptor was very different from its pK _i for 5-HT₃ receptors (pK _i = 8 –10). Other selective 5-HT₃ receptor antagonists with an indole group (BRL 43694 and GR 38032F), with a benzoate group (cocaïne, MDL 72222) or with a piperazine group (quipazine) were ineffective in reversing the stimulatory effect of benzamide derivatives. Exposure of neuronal cells to potent agonists at this receptor such as BRL 24924 rapidly reduces its capacity to stimulate cAMP production. For example, a preincubation of 10 min with BRL 24924 (100 mol/l) reduced by 42% the ability of 5-HT to stimulate cAMP production. Cross-desensitization occurs between the effects of 5-HT and benzamides. The unique pharmacology of these nonclassical 5-HT receptors that we propose to call 5-HT₄ is very close and even identical to the pharmacology of the high affinity 5-HT receptors involved in the indirect stimulation of smooth muscle in the guinea pig ileum. These receptors are different from the 5-HT₃ receptors also present in guinea pig ileum.Send offprint requests to A. Dumuis at the above address     

Involvement of adenylate cyclase and protein kinase C in the α2-adrenoceptor-mediated inhibition of noradrenaline and 5-hydroxytryptamine release in rat hypothalamic slices

Summary In superfused rat hypothalamic slices prelabelled with [³H]-noradrenaline, the ₂-adrenoceptor agonist UK 14304 inhibited in a concentration-dependent manner the electrically-evoked release of tritium. This inhibition was antagonized by the ₂-adrenoceptor blocking agent idazoxan, which by itself increased the electrically-evoked tritium overflow. Exposure to forskolin, an adenylate cyclase activator, increased the electrically-evoked release of [³H]-noradrenaline. In the presence of forskolin (1 mol/l), both the inhibitory effect of UK 14304 and the increasing effect of idazoxan on the electrically-evoked release of [³H]-noradrenaline were less pronounced than in the absence of the adenylate cyclase activator. Exposure to forskolin and to the phosphodiesterase inhibitor 3-isobutyl-l-methylxanthine shifted to the right the concentration-effect curve for UK 14304 in a similar manner as that observed in the presence of forskolin alone. Exposure to phorbol-12,13-dibutyrate (0.01–10 mol/l), a drug which activates protein kinase C, increased the electrically-evoked release of [³H]-noradrenaline. In the presence of phorbol-12,13-dibutyrate (0.1 and 1 mol/l), the concentration effect curve for UK 14304 on tritium overflow was significantly shifted to the right. The increasing effect of idazoxan on tritium overflow was significantly less pronounced in the presence of 1 mol/l phorbol-12,13-dibutyrate.In superfused rat hypothalamic slices prelabelled with [³H]-5-hydroxytryptamine, the ₂-adrenoceptor agonist UK 14304 significantly inhibited the electrically-evoked release of tritium. Exposure to forskolin increased in a concentration-dependent manner [³H]-5-hydroxytryptamine overflow, but did not modify the UK 14304-mediated inhibition. Exposure to 3-isobutyl-1-methylxanthine enhanced the electrically-evoked release of [³H]-5-hydroxytryptamine. In the presence of both forskolin (1 mol/l) and 3-isobutyl-l-methylxanthine (1 mmol/l), the concentration-response curve for UK 14304 was significantly shifted to the right. Exposure to phorbol-12,13-dibutyrate (0.01–10 mol/l) enhanced in a concentration-dependent manner the electrically-evoked overflow of [³H]-5-hydroxytryptamine. In the presence of phorbol-12,13-dibutyrate (0.1 and 1 mol/l), UK 14304 was significantly less potent to inhibit tritium release than in the absence of the protein kinase C activator.It is concluded that both cyclic AMP and phosphoinositide turnover are involved in the modulation of noradrenaline and 5-hydroxytryptamine release by presynaptic ₂-adrenoceptors in rat hypothalamic slices. However, these interactions do not represent definitive proof for a cause-effect relationship for the second messengers mediating the ₂-adrenoceptor induced inhibition of transmitter release either as autoreceptor or as heteroreceptor.Send offprint requests to S. Z. Langer at the above address     

Inhibition of N-methyl-d-aspartate (NMDA) and l-glutamate-induced noradrenaline and acetylcholine release in the rat brain by ethanol

Summary The influence of ethanol on stimulation-evoked ³H-transmitter release was examined in slices of the rat brain cortex and corpus striatum preincubated with ³H-noradrenaline and ³H-choline, respectively. ³H-Transmitter release was stimulated by NMDA, l-glutamate, electrical impulses, reintroduction of Ca²⁺ ions (Ca²⁺-evoked release; after superfusion with Ca²⁺-free, K⁺-rich solution) or veratridine. In cortical slices preincubated with ³H-noradrenaline and superfused with Mg²⁺-free, otherwise physiologically composed salt solution, ethanol inhibited the NMDA- or l-glutamate-induced tritium overflow (IC₅₀ 45 and 37 mmol/l, respectively). In contrast, the tritium overflow in response to electrical stimulation, reintroduction of Ca²⁺ ions or veratridine was not affected by ethanol at concentrations up to 320 mmol/l; these experiments were carried out in cortical slices superfused with solution containing a physiological Mg²⁺ concentration. Ethanol also failed to inhibit Ca²⁺-evoked release in the absence of Mg2⁺ ions. In the presence of 1 mol/l veratridine, but not in its absence, NMDA induced tritium overflow even when cortical slices were superfused with salt solution containing a physiological Mg²⁺ concentration; again, ethanol inhibited this NMDA-evoked tritium overflow (IC₅₀ 73 mmol/l). In striatal slices preincubated with ³H-choline and superfused with Mg²⁺-free physiological salt solution, the NMDA-evoked tritium overflow was also, although at lower potency, inhibited by ethanol (IC₅₀ 192 mmol/l).In spite of the differences between the IC₅₀ values of ethanol determined for the inhibition of cortical noradrenaline and striatal acetylcholine release, it may be concluded that the NMDA receptor-ion channel complex is one of the sites of action underlying the ethanol-induced inhibition of neurotransmitter release. Since in the brain cortex the NMDA-induced ³H-noradrenaline release appears to be mediated by an excitatory interneurone activated by NMDA, this neuronal system may be involved in the cortical actions of ethanol.     

Role of histamine receptor in mesencephalic nucleus dorsalis raphe in cardiovascular regulation

Summary The effects of microinjection of histamine and its antagonists into mesencephalic nucleus dorsalis raphe, were investigated on mean arterial pressure and heart rate in cats to elucidate the nature and role of histaminergic receptors in cardiovascular regulation. Microinjection of histamine (5 and 10 g) into nucleus dorsalis raphe elicited both inhibitory and excitatory cardiovascular responses respectively. On the other hand, microinjection of H₂-receptor blocker, cimetidine (10 g) resulted in hypertension and tachycardia while H₁-receptor antagonist, mepyramine (10 g) microinjection evoked hypotension and bradycardia. Furthermore, local pretreatment with cimetidine and mepyramine blocked the inhibitory and excitatory cardiovascular responses of graded doses of histamine microinjection. These H₁ and H₂ receptors are localized in nucleus dorsalis raphe since microinjection of histamine into adjoining neural structures did not evoke any cardiovascular change. Furthermore, both the inhibitory and excitatory cardiovascular responses to histamine microinjection could not be observed in animals with spinal cord transection and in animals pretreated with p-chlorophenylalanine while they could be observed in bilateral cervical vagotomized animals. Thus, it appears that these cardiovascular responses to microinjection of histamine into nucleus dorsalis raphe, are due to modulation of serotonergic bulbospinal influence on sympathetic preganglionic neurones in the spinal cord. Moreover, the excitatory cardiovascular responses of high dose of histamine (10 g) seem to result from a local release of noradrenaline since they were blocked by prior microinjection of guanethidine and piperoxan into nucleus dorsalis raphe. A release of noradrenaline in turn, modulates the activity of the neurones of the nucleus by acting on adrenoceptors and thereby alters the activity of sympathetic preganglionic neurones. These adrenoceptors appear to be of ₁ type (Saxena et al. 1985, 1987) since phenylephrine microinjection evoked excitatory cardiovascular responses could be blocked by piperoxan. Send offprint requests to K. K. Tangri at the above address     

Effect of ω-conotoxin GVIA on release of 3H-γ-aminobutyric acid from slices of rat neostriatum

Summary -Conotoxin GVIA (-CT) diminished the potassium-induced in vitro release of ³H--aminobutyric acid (³H-GABA) from slices of rat neostriatum in a manner which depended on the concentration of potassium. -CT (0.1 nmol/l) decreased the release of ³H-GABA induced by 25 mmol/l K⁺ from 11.6% to 6.1% of tissue content, ie. by 48%, while it did not affect the release of ³H-GABA caused by 20 mmol/l K⁺, which was 4.8% of tissue content. However, in the presence of a polyclonal antiserum or cysteamine (600 mol/l), both of which diminish the effects of endogenous somatostatin, 0.1–10 nmol/l -CT decreased the release of ³H-GABA induced by 20 mmoles/l K⁺ by 40%. It is concluded that -CT did not only inhibit GABA-neurones, but had an additional inhibitory effect on somatostatin neurones which are known to depress the release of ³H-GABA. It is further concluded that neuronal interactions, which are possible in brain slice preparations, may impede the interpretation of effects of drugs, especially if agents are used which affect basic mechanisms of transmitter release and thus the release of various transmitters from neurones. Send offprint requests to D. K. Meyer at the above address     

Presynaptic action of adrenaline on adrenoceptors modulating stimulation-evoked 3H-noradrenaline release from rabbit isolated aorta

Summary The purpose of this investigation was to study the effect of adrenaline on presynaptic adrenoceptors by recording the release of ³H-noradrenaline evoked by electrical-field stimulation. Adrenaline (10^–10–³ × 10^–9 mol/l) had no effect on the ³H-overflow evoked by stimulation of aorta preloaded with ³H-noradrenaline. At 10^–8 and 3 × 10^–8 mol/l, the ³H-overflow was decreased by up to 47%. The maximum decrease was more marked in the presence of either cocaine (3 × 10^–5 mol/l) plus corticosterone (4 × 10^–5 mol/l), cocaine (3.3 × 10^–6 mol/l) plus normetanephrine (4 × 10^–5 mol/l), or desipramine (10^–6 mol/l) plus normetanephrine (10^–5 mol/l). The relationship between adrenaline-induced decrease and stimulation-frequency was dependent on the experimental design: either the decrease was the same at all frequencies (1–16 Hz) or it was more marked, the lower the frequency (1 > 3 > 8 Hz). Phentolamine and rauwolscine (both 10^–6 mol/l) antagonized the inhibitory effect of adrenaline (10 ^{– 8}–10^–6 mol/l). Phenoxybenzamine (10^–6 mol/l), prevented the inhibitory effect. No enhancing effect of adrenaline (10^–9–10^–6 mol/l) was observed in the presence of these three -adrenoceptor antagonists. Our results suggest that adrenaline activates inhibitory ₂-adrenoceptors, but not facilitatory -adrenoceptors on postganglionic sympathetic nerve terminals in rabbit aorta. Send offprint requests to J. Abrahamsen at the above address