Release of dopamine from human neocortex nerve terminals evoked by different stimuli involving extra- and intraterminal calcium.

The release of [(3)H]-dopamine ([(3)H]-DA) from human neocortex nerve terminals was studied in synaptosomes prepared from brain specimens removed in neurosurgery and exposed during superfusion to different releasing stimuli. Treatment with 15 mM KCl, 100 microM 4-aminopyridine, 1 microM ionomycin or 30 mM caffeine elicited almost identical overflows of tritium. Removal of external Ca(2+) ions abolished the overflow evoked by K(+) or ionomycin and largely prevented that caused by 4-aminopyridine; the overflow evoked by caffeine was completely independent of external Ca(2+). Exposure of synaptosomes to 25 microM of the broad spectrum calcium channel blocker CdCl(2) strongly inhibited the 4-aminopyridine-induced tritium overflow while that evoked by ionomycin remained unaffected. The Ca(2+) chelator, 1,2-bis-(2-aminophenoxy)ethane-N,N,N',N' tetraacetic acid (BAPTA), reduced significantly the K(+)- and the caffeine-induced tritium overflow. The effect of caffeine was attenuated by exposure to the ryanodine receptor blocker dantrolene or when the membrane-impermeant inositol trisphosphate receptor antagonist, heparin, was entrapped into synaptosomes; the combined treatment with dantrolene and heparin abolished the release elicited by caffeine. Tetanus toxin, entrapped into human neocortex synaptosomes to avoid prolonged incubation, inhibited in a concentration-dependent manner the K(+)- or the 4-aminopyridine-evoked tritium overflow; in contrast, the release stimulated by ionomycin and by caffeine were both totally insensitive to the same concentrations of tetanus toxin. Western blot analysis showed about 50% reduction of the content of the vesicular protein, synaptobrevin, in synaptosomes poisoned with tetanus toxin. In conclusion, the release of dopamine from human neocortex nerve terminals can be triggered by Ca(2+) ions originating from various sources. It seems that stimuli not leading to activation of voltage-sensitive Ca(2+) channels elicit Ca(2+)-dependent, probably exocytotic, release that is insensitive to tetanus toxin.

Selective block of rat and human neocortex GABA(B) receptors regulating somatostatin release by a GABA(B) antagonist endowed with cognition enhancing activity.

Previously, we have shown that presynaptic GABA(B) receptors regulating the release of various transmitters from CNS terminals can be differentially blocked by GABA(B) antagonists suggesting the existence of pharmacologically distinct GABA(B) receptor subtypes. We here examined the ability of CGP 36742 [(3-aminopropyl)n-butylphosphinic acid], a selective GABA(B) antagonist endowed with cognition enhancing activity, to block release-regulating GABA(B) receptors. In particular, CGP 36742 was tested against the inhibition of the depolarization-evoked release of GABA, glutamate, cholecystokinin and somatostatin produced by (-)baclofen in rat and human neocortex axon terminals. CGP 36742 potently antagonized (IC50 = 0.14 microM) the inhibition by (-)baclofen of somatostatin release from superfused rat neocortex synaptosomes. In contrast, the effects of (-)baclofen on GABA, glutamate and cholecystokinin release were insensitive to CGP 36742, at concentrations of up to 100 microM. In human neocortex synaptosomes CGP 36742 exhibited a pattern of selectivity identical to that in rat synaptosomes, although the antagonist was at least 10-fold less potent in human than in rat brain. CGP 36742 is the first compound displaying great selectivity for the GABA(B) presynaptic receptors regulating somatostatin release. Considering the proposed implication of the neuropeptide in cognitive processes, disinhibition of somatostatin release merits consideration as one of the mechanisms possibly involved in the behavioral activity of CGP 36742.

[Differential diagnosis of subarachnoid hemorrhage]. / Diagnosi differenziale dell'emorragia subaracnoidea.

The diagnosis of subarachnoid haemorrhage (SAH) presents in particular cases, some difficulties, even for neurosurgeons; the possibility that CT scan is negative during the first hours post SAH, represents a further problem; for these reasons the importance of lumbar puncture is stressed. In some cases an intracerebral clot may be misunderstood like an hypertensive haemorrhage. The recognition of the so called warning leaks, preceding the 40% of cases of "major" SAH, has a great importance for improving the final results, overall if is considered the high rate of mortality in the first 48 hours post a major SAH. For these reasons a peculiar attention has to be paid to these patients by the peripheral emergency rooms.

Human brain cholecystokinin: release of cholecystokinin-like immunoreactivity (CCK-LI) from isolated cortical nerve endings and its modulation through GABA(B) receptors.

The release of cholecystokinin-like immunoreactivity (CCK-LI) in human brain was investigated using synaptosomes prepared from neocortical specimens removed during neurosurgery. CCK-LI basal release from superfused synaptosomes was increased 3 to 4-fold during depolarization with 15 mM KCI. The K(+)-evoked overflow of CCK-LI was strictly Ca(++)-dependent. The gamma-aminobutyric acidB (GABA(B)) receptor agonist (-)baclofen (0.3-100 microM) inhibited CCK-LI overflow in a concentration-dependent manner (EC50 = 2.20 microM; maximal effect: 45%). The novel GABA(B) receptor ligand CGP 47656 mimicked (-)baclofen (EC50 = 2.45 microM; maximal effect: 50%), whereas the GABA(A) agonist muscimol was ineffective up to 100 microM. The inhibitory effect of 10 microM (-)baclofen on the CCK-LI overflow was concentration-dependently prevented by two selective GABA(B) receptor antagonists, CGP 35348 (IC50 = 13.91 microM) and CGP 52432 (IC50 = 0.08 microM). The effect of 10 microM CGP 47656 was abolished by 1 microM CGP 52432. In experiments on [3H]GABA release, CGP 47656 behaved as an antagonist at the GABA(B) autoreceptors: added at 10 microM, it prevented the inhibitory effect of 10 microM (-)baclofen on the K+ (15 mM)-evoked release of [3H]GABA from human synaptosomes. We conclude that 1) the release of CCK-LI evoked from human brain tissue appears of neuronal origin; 2) the CCK-releasing terminal possess inhibitory presynaptic GABA(B) receptors; 3) these receptors differ pharmacologically from human neocortex GABA(B) autoreceptors, which are CGP 35348-insensitive (Fassio et al., 1994) but can be blocked by CGP 47656; 4) because cholecystokinin has been implicated in anxiety, the GABA(B) receptors here characterized may represent targets for novel anxiolytic agents.

Human brain somatostatin release from isolated cortical nerve endings and its modulation through GABAB receptors.

UNLABELLED: 1. The release of somatostatin-like immunoreactivity (SRIF-LI) in the human brain was studied in synaptosomal preparations from fresh neocortical specimens obtained from patients undergoing neurosurgery to remove deeply sited tumours. 2. The basal outflow of SRIF-LI from superfused synaptosomes was increased about 3 fold during exposure to a depolarizing medium containing 15 mM KCl. The K(+)-evoked overflow of SRIF-LI was almost totally dependent on the presence of Ca2+ in the superfusion medium. 3. The GABAB receptor agonist, (-)-baclofen (0.3 - 100 microM), inhibited the overflow of SRIF-LI in a concentration-dependent manner (EC50 = 1.84 +/- 0.20 microM; maximal effect: about 50%). The novel GABAB receptor ligand, 3-aminopropyl(difluoromethyl)phosphinic acid (CGP 47656) mimicked (-)-baclofen in inhibiting the SRIF-LI overflow (EC50 = 3.06 +/- 0.52 microM; maximal effect: about 50%), whereas the GABAA receptor agonist, muscimol, was ineffective up to 100 microM. 4. The inhibition by 10 microM (-)-baclofen of the K(+)-evoked SRIF-LI overflow was concentration-dependently prevented by two selective GABAB receptor antagonists, 3-amino-propyl (diethoxymethyl)-phosphinic acid (CGP 35348) (IC50 = 24.40 +/- 2.52 microM) and [3-[[(3,4-dichlorophenyl) methyl]amino]propyl] (diethoxymethyl) phosphinic acid (CGP 52432) (IC50 = 0.06 +/- 0.005 microM). 5. The inhibition of SRIF-LI overflow caused by 10 microM CGP 47656 was abolished by 1 microM CGP 52432. 6. When human synaptosomes were labelled with [3H]-GABA and depolarized in superfusion with 15 mM KCl, the inhibition by 10 microM (-)-baclofen of the depolarization-evoked [3H]-GABA overflow was largely prevented by 10 microM CGP 47656 which therefore behaved as an autoreceptor antagonist. 7. IN CONCLUSION: (a) the characteristics of SRIF-LI release from synaptosomal preparations of human neocortex are compatible with a neuronal origin; (b) the nerve terminals releasing the neuropeptide possess inhibitory receptors of the GABAB type; (c) these receptors differ pharmacologically from the GABAB autoreceptors present on human neocortex nerve terminals since the latter have been shown to be CGP 35348-insensitive but can be blocked by CGP 47656.

Spinal dermoid cysts originating intracranial fat drops causing obstructive hydrocephalus: case reports.

The authors report two cases of spinal dermoid cysts whose rupture originated the migration of free fat drops into the ventricles and intracranial subarachnoid spaces. In both cases the fat drops caused obstructive hydrocephalus, which represents a quite exceptional complication. Moreover, one of the cases is unique, since the finding of intracranial fat causing hydrocephalus considerably preceded the discovery of the spinal neoplasm. The authors suggest that the finding of intracranial fat in the absence of a local source makes the search for a intraspinal dermoid or epidermoid tumor mandatory.

Characterization of the GABA autoreceptor in human neocortex as a pharmacological subtype of the GABAB receptor.

Release-regulating gamma-aminobutyric acidB (GABAB) autoreceptors were studied in synaptosomes from fresh specimens of human cerebral cortex. The K+ (12 mM)-evoked overflow of [3H]GABA was inhibited by the GABAB receptor agonists (-)-baclofen (EC50 = 1.48 microM) and 3-aminopropylphosphinic acid (3-APPA; EC50 = 0.034 microM). The effect of 10 microM (-)-baclofen was differentially reduced by the three GABAB receptor antagonists CGP 52432 ([3-[[(3,4-dichlorophenyl)methyl)amino]propyl]-(diethoxymethyl)- phosphinic acid), phaclofen and CGP 35348 (3-aminopropyl-(diethoxymethyl)- phosphinic acid). CGP 52432 was by far the most potent antagonist (IC50 = 0.09 microM). Phaclofen was about 700-fold less potent than CGP 52432 (IC50 = 70.0 microM) while CGP 35348 was ineffective up to 100 microM. The present results suggest that human and rat GABAB neocortical autoreceptors have similar pharmacological characteristics.

Enhancement of glycine release from human brain cortex synaptosomes by acetylcholine acting at M4 muscarinic receptors.

Synaptosomes prepared from fresh specimens of human cerebral cortex were labeled with [3H]glycine ([3H]Gly) and distributed in parallel superfusion chambers. Exposure to 15 mM KCl evoked a tritium overflow which was largely prevented by 10 mM Mg++, suggesting a consistent component of Ca(++)-dependent [3H]Gly release. Acetylcholine (ACh; 1-100 microM), added during K(+)-depolarization, increased the release of tritium in a concentration-dependent manner (maximal effect, 60%; EC50 = 7 microM). Oxotremorine (1-100 microM) mimicked ACh. The effect of 10 microM ACh was insensitive to the nicotinic antagonist mecamylamine (100 microM), but it was blocked by the muscarinic antagonist atropine (0.1 microM). Three muscarinic receptor antagonists, pirenzepine, AF-DX 116 (11-[12-[diethylamino-methyl]-1-piperidinyl]acetyl-5-11-dihydro -6H-pyrido-[2-3-b][1,4]benzodiazepine-6-one) and himbacine, endowed with relative selectivity for various muscarinic receptor subtypes, prevented with differential affinities the effect of 10 microM ACh. Himbacine was the most potent antagonist of ACh, its pA2 (8.34) being 20- or 50-fold higher than that of pirenzepine (7.27) or AF-DX 116 (6.65). It is concluded that: 1) ACh can increase the release of Gly in human cerebral cortex; 2) the interaction occurs through muscarinic receptors which resemble most the M4 subtype; and 3) considering that Gly is required to activate the N-methyl-D-aspartate glutamate receptor, the ACh-evoked Gly release may represent a linkage between cholinergic and glutamatergic transmission, two systems strongly implicated in cognitive processes.

5-Hydroxytryptamine3 receptors sited on cholinergic axon terminals of human cerebral cortex mediate inhibition of acetylcholine release.

Synaptosomes prepared from freshly obtained human cerebral cortex and labeled with [3H]choline have been used to investigate the modulation of [3H]acetylcholine ([3H]ACh) release by 5-hydroxytryptamine (5-HT). The Ca(2+)-dependent release of [3H]-ACh occurring when synaptosomes were exposed in superfusion to 15 mM KCl was inhibited by 5-HT (0.01-1 microM) in a concentration-dependent manner. The effect of 5-HT was mimicked by 1-phenylbiguanide, a 5-HT3 receptor agonist, but not by 8-hydroxy-2-(di-n-propylamino)tetralin, a 5-HT1A receptor agonist. The 5-HT3 receptor antagonists tropisetron and ondansetron blocked the effect of 5-HT, whereas spiperone and ketanserin were ineffective. It is suggested that cholinergic axon terminals in the human cerebral cortex possess 5-HT receptors that mediate inhibition of ACh release and appear to belong to the 5-HT3 type.

Modulation of 5-hydroxytryptamine release by presynaptic inhibitory alpha 2-adrenoceptors in the human cerebral cortex.

Slices and synaptosomes from human cerebral cortex (which had to be removed to reach deeply located tumours) and, for comparison, synaptosomes from guinea-pig and rat cerebral cortex were preincubated with [3H]5-hydroxytryptamine and superfused with physiological salt solution containing an inhibitor of 5-hydroxytryptamine uptake. The effects of alpha-adrenoceptor agonists and antagonists on the electrically (slices) or potassium-evoked (synaptosomes) tritium overflow were studied. In human cerebral cortical slices, the electrically-evoked [3H] overflow was inhibited by noradrenaline (pIC25 value: 6.35); the non-selective alpha-adrenoceptor antagonist phentolamine, at a concentration of 0.32 mumol/l, strongly antagonized the inhibitory effect of noradrenaline (apparent pA2 value: 8.19) but did not affect the evoked overflow by itself. In synaptosomes from humans, guinea-pigs and rats, noradrenaline also inhibited the K(+)-evoked [3H] overflow in a concentration dependent manner; the alpha 2-adrenoceptor clonidine (1 mumol/l), but not the alpha 1-adrenoceptor agonist methoxamine (1 mumol/l), mimicked the effects of noradrenaline; the effect of noradrenaline (0.3 mumol/l) was abolished by the alpha 2-adrenoceptor antagonist idazoxan (0.5 mumol/l), but not by the alpha 1-adrenoceptor antagonist prazosin (1 mumol/l). It is concluded that release-inhibiting adrenoceptors of the alpha 2-subtype exist on 5-hydroxytryptamine terminals innervating the cerebral cortex in human and guinea-pig brain.

Release-regulating autoreceptors of the GABAB-type in human cerebral cortex.

1. The depolarization-evoked release of gamma-aminobutyric acid (GABA) and its modulation mediated by autoreceptors were investigated in superfused synaptosomes prepared from fresh human cerebral cortex. 2. The release of [3H]-GABA provoked by 15 mM K+ from human cortex nerve endings was almost totally (85%) calcium-dependent. 3. In the presence of the GABA uptake inhibitor SK&F 89976A (N-(4,4-diphenyl-3-butenyl)-nipecotic acid), added to prevent carrier-mediated homoexchange, GABA (1-10 microM) decreased in a concentration-dependent manner the K+-evoked release of [3H]-GABA. The effect of GABA was mimicked by the GABAB receptor agonist (-)-baclofen (1-100 microM) but not by the GABAA receptor agonist muscimol (1-100 microM). Moreover, the GABA-induced inhibition of [3H]-GABA release was not affected by two GABAA receptor antagonists, bicuculline or SR 95531 (2-(3'-carbethoxy-2'-propenyl)-3-amino-6-paramethoxy-phenyl-pyr idazinium bromide). 4. (-)-Baclofen also inhibited the depolarization-evoked release of endogenous GABA from human cortical synaptosomes. 5. It is concluded that GABA autoreceptors regulating the release of both newly taken up and endogenous GABA are present in human brain and appear to belong to the GABAB subtype.

Subarachnoid haemorrhage of unknown origin: clinical and tomographical aspects.

65 patients with negative but technically satisfactory 4 vessel angiography - all admitted to our Department in the years 1976-1983 - were evaluated in the present study. CT scan was undertaken in all cases (in 47 cases within 4 days of haemorrhage). Arterial hypertension was present on admission in 9% of cases. The period of follow-up ranged from 4 to 11 years, with a mean of 5.3 years. The study group was compared to a control group, comprising 760 patients with subarachnoid haemorrhage from ruptured aneurysms, admitted during the same period. Clinical grade on admission (Hunt's classification) was better in patients belonging to the study group. The amount of cisternal deposition on CT scan was less significant than in patients with ruptured aneurysms, and the deposition was often atypical (circumpeduncular, ambiental, and/or tentorial). Clinical deterioration associated with vasospasm was observed in 5% of patients in this study and in 27% of patients in the control group. In patients with a consistent or thick cisternal layer (CT scan "at risk") the incidence of clinical vasospasm was 21%, against 47% in controls. One or more rebleedings occurred in 12% of patients in the study group, against 25% of patients in the control group. A significant ventricular dilatation was observed in 15% of patients in the first group (requiring a shunt in 8%), against 25% of patients in the second group (requiring a shunt in 11%). Final outcome was favourable in 95% of patients in this study group and in 63% of patients in the control group, with a mortality rate of 5% in the first group and 32% in the second group.

Extracranial posterior inferior cerebellar artery aneurysm causing isolated intraventricular hemorrhage: a case report.

The authors report the unusual case of an aneurysm arising on an extracranial loop of the left posterior inferior cerebellar artery (PICA). The computed tomographic scan showed an isolated hemorrhage in the lateral ventricles, and the lesion was recognized 1.5 cm below the foramen magnum at the level of the atlas. The literature concerning peripheral PICA aneurysms is reviewed and the clinical and radiological features of these lesions are discussed. A tendency for subarachnoid bleeding from distal PICA aneurysm ruptures to spread into the ventricular system is suggested. The diagnosis of distal PICA aneurysm should also be considered in cases of isolated intraventricular hemorrhage without obvious parenchymal or subarachnoid hemorrhage. The need for four-vessel angiography when studying patients suffering from a subarachnoid hemorrhage is stressed.

Intracranial hematomas following aneurysmal rupture: experience with 309 cases.

Three hundred and nine consecutive cases of intracranial hematomas due to aneurysmal rupture--representing 34% of the total number of patients with aneurysms observed in a 12-year period--were evaluated; of these, 211 were submitted to computed tomography scan. Hematomas were present on admission in 71% of patients and occurred at rebleeding in 29%. Ruptured middle cerebral artery aneurysms caused an intracranial hematoma more frequently than aneurysms in other locations. Ventricular hematomas were frequently observed--especially at rebleeding--in cases with anterior communicating artery aneurysms. Basal ganglia hematomas were detected in eight cases with internal carotid bifurcation aneurysms and in three with middle cerebral artery aneurysms. Subdural hematomas were observed in 32 cases, mainly due to ruptured middle-cerebral-artery and internal-carotid-artery aneurysms. As for clinical evolution, a rapid deterioration was observed in 39% of cases and a chronic course in 46%; a subacute deterioration was far less frequent. Delayed deterioration from vasospasm was observed in 8% of cases, and appeared to be related to the amount of subarachnoid bleeding associated with the hematoma. One hundred and forty-two patients were submitted to surgical treatment (evacuation of hematoma together with exclusion of aneurysm); deep coma, poor medical condition, stabilized neurological disability, or combinations of these factors accounted for the high number of patients not operated upon. Regardless of treatment, 24% of patients showed good results and 58% died. Presence of a large hematoma, ventricular hemorrhage, and shift of the ventricles represented significant risk factors, associated with a poor prognosis. A comparison between two groups of patients admitted within 3 days of hemorrhage--47 operated on early, and 149 with delayed treatment--showed that better results were achieved by early operations, especially for cases in Hunt's grades IV and V.

Intracranial aneurysms and subarachnoid hemorrhage in children and adolescents.

Thirty-eight cases of symptomatic cerebral aneurysms or spontaneous subarachnoid hemorrhage in children and adolescents were observed from 1965 to 1984; 33 cases were treated from 1970 to date. This group represents 2.6% of the total number of patients with subarachnoid hemorrhage treated at our institute in the same period. The cause of subarachnoid hemorrhage was unknown in 7 cases; an intracranial aneurysm had ruptured in 29 cases, and was unruptured but symptomatic in 2 remaining cases. Three aneurysms were mycotic. The most frequent aneurysmal locations were the internal carotid bifurcation and the anterior communicating artery; peripheral branches of the middle cerebral artery were also a relatively common location. Four patients were 3 years of age or younger: each presented peculiar clinical features, and 3 of the 4 had middle cerebral artery aneurysms. The remaining 34 patients were all above 9 years of age. Two groups were identified: (a) in 14 patients between 10 and 15 years of age, the aneurysm was most commonly at the internal carotid bifurcation (37%), and an intracerebral hematoma was observed in 50% of these cases; (b) in 20 patients between 16 and 20 years of age, the most common aneurysmal location was the anterior communicating artery (35%), and intracerebral hematomas were rare (10% of cases). Among patients with aneurysms, 19 underwent surgical exclusion by clip, with 10% morbidity and 5% mortality; 5 patients in moribund conditions were not operated on; 5 patients were conservatively treated; in 2 patients the aneurysm had disappeared at a second angiography.(ABSTRACT TRUNCATED AT 250 WORDS)

Childhood cerebrovascular diseases not associated with vascular malformations.

Of 76 patients in the pediatric age group suffering from cerebrovascular diseases treated in the years 1970-1983, 26 patients (34%) did not harbor intracranial vascular malformations (aneurysms or arteriovenous malformations). Two groups of patients were identified: (a) those suffering from a spontaneous intracranial hemorrhage (16 cases); (b) those suffering from an ischemic stroke (10 cases). Of those with spontaneous intracranial hemorrhage, 10 patients underwent surgery and evacuation of the hematoma. In 2 cases the hematoma was located in the posterior fossa, in 1 case in the upper brain stem, and in 3 cases in the basal ganglia; in the remainder the hematoma was supratentorial. Two patients died soon after the hemorrhage. Eight of the surviving patients completely recovered. In those with ischemic stroke, none suffered from congenital heart disease, a well-known predisposing factor. In this second group 1 patient died and 9 survived. Only one patient showed complete recovery. The data indicate that a hemorrhagic stroke is more common than an ischemic stroke in a child presenting with acute onset of hemiparesis and/or loss of consciousness: thus the value of CT scan as the first diagnostic procedure is clear, owing to the possibility of emergency surgical treatment. In children with ischemic strokes, a complete laboratory/clinical evaluation should be undertaken in order to exclude preexisting heart disease, coagulation disorders or lipoprotein abnormalities, and less common systemic diseases.

Cerebral vasospasm after head injury.

Cerebral vasospasm occurs frequently after head injury. Correlation between neurological deterioration and vasospasm has been reported previously, but delayed neurological deterioration secondary to vasospasm in head injury is a rare occurrence. We report the case of a 57-year-old man who, after a motorcycle accident, developed an acute subdural hematoma and a thick subarachnoid deposition of blood in the left sylvian-insular cistern. After surgical evacuation of the hematoma, the patient improved until the 10th postoperative day, when he developed aphasia and a right hemiparesis. Angiography demonstrated multitapering spasm, and a computed tomographic (CT) scan showed persistence of the cisternal deposition of blood. Despite therapy with hypervolemia, the patient improved only slightly. The association of head injury with substantial subarachnoid hemorrhage producing vasospasm has been considered rarely. Delayed posttraumatic vasospasm secondary to blood degradation products seems to play some role in the vasospasm after head injury. CT scanning may be useful in predicting vasospasm in such patients, and digital subtraction angiography might be useful in demonstrating it.

[Multiple intracranial aneurysms associated with arteriovenous malformation. Clinical case]. / Aneurismi multipli intracranici associati ad una malformazione arterovenosa. Caso clinico.

A case of intracranial multiple aneurysms associated with a giant arteriovenous malformation is reported. Three aneurysms were found arising from the arteries feeding the malformation. The patient could not be operated because of his age, neurological condition and the size of the arteriovenous malformation. Previously reported cases of cerebral aneurysms associated with arteriovenous malformation are reviewed. Our case well illustrates the possible role of hemodynamic stresses induced by the malformation on the development of the aneurysms.