Phencyclidine, lysergic acid diethylamide, and mescaline: cerebral artery spasms and hallucinogenic activity

Multiple Actions of Phencyclidine and (+)MK-801 on Isolated Bovine Cerebral Arteries

This study examines the direct effects of 3 noncompetitive N-methyl-D-aspartate receptor antagonists, phencyclidine (PCP), (+)MK-801, and (-)MK-801, on bovine middle cerebral arteries (BMCA). Rings of BMCA were mounted in isolated tissue chambers equipped with isometric tension transducers to obtain pharmacologic dose-response curves. In the absence of endogenous vasoconstrictors, the 3 N-methyl-D-aspartate antagonists each produced direct constriction of BMCA. The thromboxane A2 receptor antagonist SQ-29,548, the TxA2 synthase inhibitor furegrelate, the calcium antagonist nimodipine, and calcium-deficient media all inhibited maximal phencyclidine or (+)MK-801-induced constriction. Direct constriction by PCP or (+)MK-801 was independent of the presence of endothelium. When BMCA were preconstricted with potassium-depolarizing solution, PCP, (+)MK-801, and (-)MK-801 each produced only concentration-dependent relaxation. When BMCA were preconstricted with the stable TxA2 analog U-46,619 and exposed to increasing concentrations of PCP, (+)MK-801, or (-)MK-801, tension increased. Thromboxane A2 may contract BMCA by acting as a potassium channel blocker; iberiotoxin and tetraethylammonium both constrict BMCA. In Ca-deficient media containing either potassium or U-46,619, phencyclidine and (+)MK-801 each produced competitive inhibition of subsequent Ca-induced constriction. In additional experiments, arterial strips were mounted in isolated tissue chambers to directly measure calcium uptake, using Calcium as a radioactive tracer. Both phencyclidine and (+)MK-801 blocked potassium-stimulated or U-46,619-stimulated Ca uptake into arterial strips. These results suggest that phencyclidine and (+)MK-801 have 2 separate actions on BMCA. They may constrict arterial rings by releasing TxA2 from cerebrovascular smooth muscle, and relax arterial rings by acting as calcium antagonists.

Cardiovascular toxicity of novel psychoactive drugs: lessons from the past

The long use of ephedrine, amphetamines, cocaine, LSD and more recently 3,4-methylenedioxy-N-methylamphetamine (MDMA; "Ecstasy") allows us to predict with some confidence what cardiovascular risks are likely to be associated with novel psychoactive substances (NPS). Once the probably multiple biological activities of a compound are known it is possible to define the likely risks of cardiovascular toxicity. Agonists of 5-HT(2A) receptors or alpha-adrenoceptors may cause vasoconstriction and tissue ischemia. Drugs which have agonist affinity for 5-HT(2B) receptors will probably promote heart valve fibrosis leading to heart failure. Compounds that interfere with uptake of dopamine or 5-hydroxytryptamine (5-HT) are likely to also have effects on noradrenergic neurotransmission and lead to sympathomimetic effects on the heart and vasculature. Drugs that cause dopamine release, or inhibit uptake are likely to be addictive and lead to chronic use. Other drugs (particularly the so-called empathogens) are associated with weekly usage in social settings; over time such use can lead to cardiovascular harm. Defining which of these effects NPS have is an important element of predicting the harm they may cause and informing those appointed to introduce regulations to control them.

Epidemic of illicit drug use, mechanisms of action/addiction and stroke as a health hazard

Drug abuse robs individuals of their jobs, their families, and their free will as they succumb to addiction; but may cost even more: a life of disability or even life lost due to stroke. Many illicit drugs have been linked to major cardiovascular events and other comorbidities, including cocaine, amphetamines, ecstasy, heroin, phencyclidine, lysergic acid diethylamide, and marijuana. This review focuses on available epidemiological data, mechanisms of action, particularly those leading to cerebrovascular events, and it is based on papers published in English in PubMed during 1950 through February 2011. Each drug's unique interactions with the brain and vasculature predispose even young, healthy people to ischemic or hemorrhagic stroke. Cocaine and amphetamines have the strongest association with stroke. However, the level of evidence firmly linking other drugs to stroke pathogenesis is weak. Large epidemiological studies and systematic evaluation of each drug's action on the brain and cardiovascular system are needed to reveal the full impact of drug use on the population.

Association of alcohol in brain injury, headaches, and stroke with brain-tissue and serum levels of ionized magnesium: a review of recent findings and mechanisms of action

Although there is general agreement that chronic ingestion of alcohol poses great risks for normal cardiovascular functions and peripheral-vascular homeostasis, a direct cause and effect between the real phenomena of alcohol-induced headache and risk of brain injury and stroke is not appreciated. "Binge drinking" of alcohol is associated with an ever-growing number of strokes and sudden death. It is becoming clear that alcohol ingestion can result in profoundly different actions on the cerebral circulation (e.g., vasodilation, vasoconstriction-spasm, vessel rupture), depending upon dose and physiologic state of host. Using rats, it has been demonstrated that acute, high doses of ethanol can result in stroke-like events concomitant with alterations in brain bioenergetics. We review recent in vivo findings obtained with 31P-NMR spectroscopy, optical reflectance spectroscopy, and direct in vivo microcirculatory studies on the intact brain. Alcohol-induced hemorrhagic stroke is preceded by a rapid fall in brain intracellular free magnesium ions ([Mg2+]i) followed by cerebrovasospasm and reductions in phosphocreatine (PCr)/ATP ratio, intracellular pH, and the cytosolic phosphorylation potential (CPP) with concomitant rises in deoxyhemoglobin (DH), mitochondrial reduced cytochrome oxidase aa3 (rCOaa3), blood volume, and intracellular inorganic phosphate (Pi). Using osmotic mini-pumps implanted in the third cerebral ventricle, containing 30% ethanol, it was found that brain [Mg2+]i is reduced 30% after 14 days; brain PCr fell 15%, whereas the CPP fell 40%. Such animals became susceptible to stroke from nonlethal doses of ethanol. Human subjects with mild head injury have been found to exhibit early deficits in serum ionized Mg (IMg2+); the greater the degree of early head injury (30 min-8 h), the greater and more profound the deficit in serum IMg2+ and the greater the ionized Ca (ICa2+) to IMg2+ ratio. Patients with histories of alcohol abuse or ingestion of alcohol prior to head injury exhibited greater deficits in IMg2+ (and higher ICa2+/IMg2+ ratios) and, unlike the subjects without alcohol, did not leave the hospital for at least several days. Women, for some unknown reason, exhibit a much higher incidence of morbidity and mortality from subarachnoid hemorrhage (SAH) than men. Data on 105 men and women with different types of stroke indicate that, on the average, a 20% deficit in serum IMg2+ is seen; total Mg (TMg) or blood pH is usually near normal. Women with SAH, however, exhibit much lower IMg2+ and higher ICa2+/IMg2+ ratios; the presence of ethanol in the blood is associated with even more depression in IMg2+ in SAH in women. It is possible that prior alcohol ingestion is, in large measure, responsible for a great deal of this unexplained higher incidence of SAH in women. It has recently been reported that the cyclical changes in estrogenic hormones appear to control the serum IMg2+ level in young women. A surge in estrogenic levels prior to SAH could thus precipitate, in part, the SAH. In other human studies, it has been shown that migraines and headache, dizziness, and hangover, which accompany ethanol ingestion, are associated with rapid deficits in serum IMg2+ but not in TMg. The former, and the alcohol-associated headache, can be ameliorated with IV administration of MgSO4. Premenstrual tension-headache (PTH) and its exacerbation by alcohol in women is also accompanied by deficits in IMg2+, and elevation in serum ICa2+/IMg2+; IV MgSO4 corrects the PTH and the serum deficit in IMg2+. Animal experiments show that IV Mg2+ can prevent alcohol-induced hemorrhagic stroke and the subsequent fall in brain [Mg2+]i, [PCr], pHi, and CPP. Other recent data indicate that alcohol-induced cellular loss of [Mg2+]i is associated with cellular Ca2+ overload and generation of oxygen-derived free radicals; chronic pretreatment with vitamin E prevents alcohol-induced vascular injury and pathology in the brain. (ABSTRACT TRUNCATED)

Do hallucinogens cause residual neuropsychological toxicity?

We collected and reviewed studies in which neuropsychological tests were administered to users of LSD or other hallucinogens. Interpretation of the studies is limited by various confounding variables, such as subjects' premorbid cognitive and personality function and prior use of other substances. At present, the literature tentatively suggests that there are few, if any, long-term neuropsychological deficits attributable to hallucinogen use. To better resolve this issue, however, it will be important to study larger samples of chronic, frequent hallucinogen users who have not often used other types of drugs.

Endothelium-dependent relaxation to hydrogen peroxide in canine basilar artery: a potential new cerebral dilator mechanism

In prostglandin F2alpha(PGF2alpha)-precontracted isolated canine basilar arterial rings, hydrogen peroxide (H2O2) produced endothelium-dependent relaxations at concentrations of from 4.4 x 10(-7) - approximately 4.4 x 10(-5) M. Removal of extracellular Ca2+ ([Ca2+]0) attenuated the relaxant effects of H2O2. Complete inhibition of H2O2 relaxant action was obtained after buffering intracellular Ca2+ ([Ca2+]i), in the endothelial cells, with 10 microM 1,2-bis (2-aminophenoxy) ethane-N,N,N',N'-tetraacetic acid (BAPTA-AM). The H2O2-induced relaxations could be abolished completely by 1200 u/ml catalase and was suppressed significantly by 0.5 microM atropine, 150 microM NG-monomethyl-arginine (L-NMMA), 50 microM NG-nitro-L-arginine methyl ester (L-NAME), 1 microM Fe2+, or 5 microM methylene blue. These inhibitory effects of L-NMMA, L-NAME, or atropine could be reversed partly by 50 microM L-arginine. The Fe2+ inhibition of H2O2-stimulated relaxation was reduced significantly by either 1 mM deferoxamine (a Fe2+ chelator) or 100 microM dimethyl sulfoxide (DMSO, a *OH scavenger). Such relaxant effects of H2O2 were enhanced, significantly, by an acetylcholinesterase antagonist, neostigmine. A variety of pharmacological antagonists (of diverse vasodilator agents) could not inhibit the relaxant action of H2O2. Our observations suggest that at suitable pathophysiological concentrations, H2O2 could induce release of an endothelium-derived relaxing factor (EDRF), probably nitric oxide (NO), from endothelial cells of the canine cerebral artery. The H2O2 relaxant effects are clearly Ca2+-dependent, require formation of cyclic guanosine monophosphate (cGMP), and may be associated with release of endogenous acetylcholine (ACh).

Ca2+ channel blockade prevents lysergic acid diethylamide-induced changes in dopamine and serotonin metabolism

To investigate the effect of a single and multiple administration of lysergic acid diethylamide (LSD) on cerebral metabolism of dopamine and serotonin, male Wistar rats were treated with low and high doses (0.1 and 2.0 mg/kg i.p.) of LSD and the levels of dopamine, 3,4-dihydroxyphenylacetic acid, homovanillic acid, 3-methoxytyramine, serotonin and 5-hydroxyindoleacetic acid were assayed by HPLC in the nucleus accumbens, striatum and frontal cortex. Some rats received nifedipine, 5 mg/kg i.p., before each injection of LSD to assess the effect of a Ca2+ channel blockade. High-dose LSD treatment (8 x 2 mg/kg per day) caused a strong stimulation of dopamine metabolism in the nucleus accumbens and striatum, and serotonin metabolism in the nucleus accumbens: the changes were observed 24 (but not 1 h) after the last dose. The changes induced by the low-dose treatment (8 x 0.1 mg/kg per day) had a different pattern, suggesting the release of dopamine from vesicles to cytoplasm. Co-administration of nifedipine completely prevented the LSD-induced biochemical changes. The results suggest that Ca2+ channel blocking agents may prevent development of some behavioral consequences of chronically used LSD.

Lateral asymmetries in auditory acuity distinguish hallucinating from nonhallucinating schizophrenic patients

Bilateral absolute auditory thresholds for frequencies ranging from 250 to 8000 Hz were examined on two occasions in schizophrenic patients and normal control subjects. Patients were classified as hallucinators and nonhallucinators on the basis of symptom ratings on both occasions. Previous evidence of better right than left ear acuity in schizophrenia was replicated but was found to characterize nonhallucinating patients only. Hallucinators showed no lateral asymmetry and inferior right ear acuity as compared with that in nonhallucinators. The results were reliable on retest. Brief Psychiatric Rating Scale scores of positive and negative symptoms in some cases differentiated hallucinators from nonhallucinators. The relationship of verbal hallucinations and right ear-left temporal lobe functions is discussed, together with complexities in cerebral laterality-syndrome relationships.

Stroke from alcohol and drug abuse. A current social peril

Alcohol and drug abuse should be among the possible causes considered in cases of stroke, especially in young adults. As both are potentially remediable factors, primary care physicians may play an important role in the reduction of stroke by implementing educational and preventive measures among their young patients.

Magnesium ions prevent phencyclidine-induced cerebrovasospasms and rupture of cerebral microvessels: direct in-vivo microcirculatory studies on the rat brain

Phencyclidine (PCP) abuse is reaching alarming proportions. PCP has recently been shown to induce hypertensive encephalopathies, microvascular cerebrovasospasm and acute intracerebral hemorrhage. Since we have shown in vitro that cerebral vasospasms induced by PCP could be completely reversed, or prevented, by use of organic calcium antagonists, we utilized a television microscope recording system to determine whether magnesium ions (Mg2+) could inhibit the ability of PCP to induce contraction of pial arterioles and its sequelae of microvascular damage. Administration of either MgCl2 or Mg aspartate HCl, i.a. or i.v. (1, 10, and 20 mumol/min), before or after administration of PCP produced dose-dependent inhibition (30-80%) of PCP-induced arteriolar spasms and the subsequent vascular damage. A variety of pharmacologic receptor antagonists and cyclooxygenase inhibitors failed to influence PCP-induced cerebrovasospasms. These data suggest that a naturally-occurring Ca2+ antagonist, viz. Mg2+, may be useful in the treatment of PCP intoxication and its cerebral vascular consequences.

Effect of the NMDA antagonist MK-801 on local cerebral blood flow in focal cerebral ischaemia in the rat

The effects of MK-801 upon local CBF after permanent middle cerebral artery (MCA) occlusion have been examined using [14C]iodoantipyrine autoradiography in halothane-anaesthetised rats. MK-801 (0.5 mg kg-1 i.v.) or saline was administered 30 min before MCA occlusion and CBF measured approximately 40 min after occlusion. In the hemisphere contralateral to the occluded MCA, MK-801 significantly reduced local CBF in 19 of the 22 regions examined from the levels in saline-treated rats. In the contralateral hemisphere, after treatment with MK-801, blood flow was reduced by an average of 37% with little variation in the magnitude of the reductions in different regions. In the hemisphere ipsilateral to MCA occlusion, MK-801 reduced CBF in almost every region located outside the territory of the occluded MCA. Within the territory of the occluded MCA, blood flow in the MK-801-treated rat did not significantly differ from values in vehicle-treated rats in any of the five cortical areas examined, although in the caudate nucleus there was a tendency for CBF to be lower in rats pretreated with MK-801. MK-801 had no effect on the amount of hypoperfused cerebral tissue (CBF less than 30 ml 100 g-1 min-1) in the ipsilateral hemisphere at any coronal plane examined; e.g., at coronal plane anterior 7.2 mm, 51 +/- 5% of the hemisphere displayed CBF of less than 30 ml 100 g-1 min-1 in saline-treated rats with MCA occlusion compared with 52 +/- 8% of the hemisphere in rats treated with MK-801 prior to MCA occlusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical features and management of intoxication due to hallucinogenic drugs

Hallucinogenic drugs are unique in that they produce the desired hallucinogenic effects at what are considered non-toxic doses. The hallucinogenic drugs can be categorised into 4 basic groups: indole alkaloid derivatives, piperidine derivatives, phenylethylamines and the cannabinols. The drugs reviewed include lysergic acid diethylamide (LSD), phencyclidine (PCP), cocaine, amphetamines, opiates, marijuana, psilocybin, mescaline, and 'designer drugs.' Particularly noteworthy is that each hallucinogen produces characteristic behavioural effects which are related to its serotonergic, dopaminergic or adrenergic activity. Cocaine produces simple hallucinations, PCP can produce complex hallucinations analogous to a paranoid psychosis, while LSD produces a combination of hallucinations, pseudohallucinations and illusions. Dose relationships with changes in the quality of the hallucinatory experience have been described with amphetamines and, to some extent, LSD. Flashbacks have been described with LSD and alcohol. Management of the intoxicated patient is dependent on the specific behavioural manifestation elicited by the drug. The principles involve differentiating the patient's symptoms from organic (medical or toxicological) and psychiatric aetiologies and identifying the symptom complex associated with the particular drug. Panic reactions may require treatment with a benzodiazepine or haloperidol. Patients with LSD psychosis may require an antipsychotic. Patients exhibiting prolonged drug-induced psychosis may require a variety of treatments including ECT, lithium and l-5-hydroxytryptophan.

Absence of N-methyl-D-aspartate receptors on ovine cerebral microvessels

Radioreceptor methods were used to quantitate the N-methyl-D-aspartate (NMDA) receptor-complex of ovine cerebral microvessels and cerebral gray matter. Specific binding of D[3H]2-amino-5-phosphono-pentanoate and [3H]1-[1-(2-thienyl)cyclohexyl]piperidine, ligands for the NMDA primary acceptor site and ionophore, respectively, was found in cerebral gray matter but was not detectable in membranes prepared from brain microvessels enriched in capillaries. Sigma receptors, another locus of action for phencyclidine congeners, were also not present on microvessels but were found in cortical homogenates. On the other hand, cerebral microvessels and gray matter contained significant numbers of beta-adrenoceptors. Our results indicate the NMDA receptors and NMDA antagonists are unlikely to regulate the function of the cerebral microvasculature.

Phencyclidine reduces postischemic neuronal necrosis in rat hippocampus without changing blood flow

In this report the effects of phencyclidine (PCP) on physiologic variables, local cerebral blood flow (LCBF), and on hippocampal cell damage were measured in a rat model of forebrain ischemia (2-vessel occlusion and hypotension). Ischemia was induced for 10 min. LCBF was determined after 2 min of recirculation, using the [14C]iodoantipyrine technique. Hippocampal cell loss was quantified histologically 7 days postischemia as the percentage of acidic stainable neurons. Intravenous application of PCP (2 mg/kg) at 15 min prior to ischemia left postischemic LCBF unchanged, but neuronal damage was significantly reduced in hippocampal CA1 sector from 46 to 15.7%. PCP is concluded to reduce ischemic damage of neurons mainly via a direct effect on brain tissue.

Pathological and radiological correlation of subarachnoid hemorrhage in phencyclidine abuse. Case report

Although hypertension can be associated with phencyclidine (PCP) use, subarachnoid hemorrhage (SAH) is a rare result. The radiological and pathological findings are reported of a patient with acute SAH who had chromatographic evidence of PCP in his blood. The occurrence of SAH in a patient who uses PCP may be caused by a disrupted arterial vessel wall and/or vasospasm due to the pharmacological action of the drug on the cerebral vasculature.

Dextrorphan: an antagonist for phencyclidine receptors

Radio-binding assay, bioassay and HPLC detection were used to observe the antagonistic effects of dextrorphan on PCP's actions. Dextrorphan displayed high affinity to PCP receptor in the rabbit mesenteric blood vessels. It had weak PCP-like bioactivity, but could antagonize PCP's action dose-dependently in vitro study with the rabbit ear artery preparation and shifted the dose-response curve of PCP to the right. After PCP administration, the content of norepinephrine in the vascular bath medium was increased, which was reversed by dextrorphan. Thus suggests that dextrorphan is an antagonist with very mild agonistic action for PCP receptors.

Use of the radial maze in studies of phencyclidine and other drugs of abuse

Effects of drugs known to disrupt performance in an 8-arm radial maze are reported in terms of changes caused in the pattern of arm entry. Phencyclidine (PCP) and N-allyl-N-normetazocine (SKF-10,047) alter the pattern of arm entry in a way which distinguishes their actions from those of scopolamine and certain serotonergic agonists. The apparent rank order of potencies for causing this effect is (+)SKF-10,047 greater than PCP greater than (-)SKF-10,047. Results of previous radial maze studies evaluating the interactions of clonidine and verapamil with PCP are summarized. Data are reported which indicate that the ability of verapamil to potentiate PCP's behavioral effects stems from an alteration of the pharmacokinetics of PCP; when verapamil (20 mg/kg, IP) was administered 15 minutes before [3H]PCP (40 microCi/kg, IP), brain levels of tritium were increased by 154 to 225 percent. Finally, possible advantages of using a 4-arm radial maze in studies of PCP and related drugs are discussed.

Verapamil does not antagonize LSD-induced stimulus control

Discriminative stimulus control was established in rats (N = 6) with LSD (100 microg/kg) and saline using a 2-lever response choice task and an FR10 schedule of food reinforcement. Subjects were then tested once per week with either pizotyline (BC-105) or verapamil alone or in combinations with LSD. In In agreement with previous reports, pizotyline antagonized LSD and, when tested alone, exhibited modest agonistic effects (18% LSD-appropriate). In contrast, verapamil failed to block LSD at any dose tested. Verapamil alone appeared to have somewhat greater agonistic activity (35% LSD-appropriate) than did pizotyline but neither drug substituted completely for LSD. These data suggest that calcium channel antagonism by pizotyline is not essential to its anti-LSD effects.

Effects of phencyclidine, N-allyl-N-normetazocine (SKF-10,047), and verapamil on performance in a radial maze

Two groups of eight rats were trained to obtain food pellets in an 8-arm radial maze. Stable performance was assumed to be present when a criterion of 89% efficiency, i.e., all arms entered within 9 arm entries, was reached in 5 consecutive sessions. The effects of phencyclidine (PCP) and N-allyl-N-normetazocine (SKF-10,047) were then evaluated in Group 1. The interaction between verapamil and PCP was examined in Group II. Both PCP (6 mg/kg, IP, 15 min before testing) and SKF-10,047 (30 mg/kg, IP, 30 min) decreased efficiency but only PCP caused a concurrent increase in rate of arm entry. Significant effects of PCP on rate and efficiency lasted for greater than 6 hours and less than 40 minutes, respectively. Verapamil (20 mg/kg, IP, 30 minutes) was found to selectively potentiate the effect of PCP on efficiency. This finding does not support the suggestion that verapamil may be useful in the treatment of PCP intoxication. It is concluded that the radial maze may provide an interesting method for the study of PCP and other psychoactive drugs.

Benign isolated arteritis of the central nervous system

We present a case of benign isolated arteritis of the CNS. The clinical and angiographic features of this rare disease are discussed and compared with similar cases published in the recent literature. The importance of the angiographic pattern in the diagnosis of this treatable disease is stressed.

Differences between calcium channel inhibitors in their effects on phencyclidine-induced behavioral stimulation in mice

Sixteen calcium channel inhibitors (CCI's) were tested in a model utilizing phencyclidine (PCP)-induced behavioral stimulation in mice. There were marked differences in the effects of CCI's both within subclasses and between subclasses of CCI's. All of the dihydropyridines and possibly flunarizine were effective in blocking PCP-induced behavioral stimulation. Papaverine derivatives, including verapamil, and several other CCI's, were ineffective.

Methysergide (Sansert) treatment in acute stroke. Community pilot study

Since its first discovery in 1948, serotonin (5-HT) has been the subject of considerable interest. Its potent vasoactivity led to the hypothesis that altered serotonin metabolism was responsible for the pathophysiology of cerebrovascular disease (infarction & hemorrhage) with documentation of elevated levels of serotonin in CSF. If (5-HT) serotonin-mediated release is ultimately responsible for cerebral edema, vasospasm and infarction in experimental and human stroke, then an opportunity exists to pharmacologically block these effects with serotonin-antagonizing agents. This hypothesis has been tested in the laboratory with several agents that inhibit biogenic amines resulting in promising data suggesting a reduction in damage and disability. Since the "natural history of human stroke" results in a 30-40% mortality within the first three weeks, an aggressive new attempt should be directed to increasing the number of survivors in this initial period of high risk. In this regard Sansert (methysergide) was considered worthy of clinical trials.

Alcohol, the cerebral circulation and strokes

Inasmuch as ethanol is thought to exert its major effects on the CNS, it is important to determine whether this abused substance can exert any direct action on cerebral blood vessels. Since chronic ingestion of alcohol: (1) can produce a loss (and degeneration) of neurons and glial cells in the brain, and (2) is associated, often, with hallucinations in human subjects particularly those undergoing withdrawal, it is possible that ethanol could produce hypoxia in select regions of the brain. The available indirect evidence in man and animals, albeit equivocal, does indicate that ethanol in certain concentrations might produce deficits in cerebral blood flow in select regions of the brain. Direct in-situ observations on the rat brain, using high-resolution, quantitative TV image-intensification microscopy, indicates that administration of ethanol, irrespective of the route of administration (e.g., perivascularly, intraarterially or systemically), produces graded concentration-dependent spasms of arterioles and venules. Concentrations of ethanol approximately greater than 250 mg/dl produce intense spasms resulting in rupture of these vessels. Recent in-situ studies in conscious dogs, using radiolabelled microspheres, also indicate that ethanol can produce deficits in regional brain blood flow. Studies with isolated canine middle cerebral and basilar arteries clearly demonstrate that low concentrations of ethanol (e.g., (less than 10 mM) can produce concentration-dependent spasms by a direct vascular action. Collectively, these new findings could be used to support the concept that heavy use of alcohol or binge-drinking can produce stroke-like effects. Specific calcium antagonists prevented or reversed the alcohol-induced cerebrovasospasms in rats and may prove valuable in treating the hypertension and strokes observed in heavy users of alcohol.

Identification of benzomorphan-kappa opiate receptors in cerebral arteries which subserve relaxation

Several 'so-called' kappa-opiate receptor agonists e.g., ketocyclazocine (Kc), ethylketocyclazocine (Ekc), bremazocine, MR-2034 and U-50488H, were tested on basilar and middle cerebral arteries of the dog in vitro for relaxant or contractile activities. Ekc, Kc and bremazocine were found to produce concentration-dependent reductions in basal tone and to relax cerebral arteries contracted with prostaglandin F2 alpha (PGF2 alpha). All three agonists appear to act on benzomorphan-kappa opiate receptors which subserve relaxation in cerebral blood vessels. MR-2034 and U-50488H were found to induce contraction in the cerebral arteries. These opiate agonists appear to act on phencyclidine (PCP) or sigma-opiate receptors which subserve contraction. A variety of pharmacological antagonists (phentolamine, propranolol, methysergide, atropine, diphenhydramine, cimetidine, naloxone) did not modify any of the cerebral vascular effects produced by the opiates. These results suggest: (1) specific benzomorphan-kappa opiate receptors which subserve relaxation exist in cerebral blood vessels; (2) some kappa agonists appear to produce, primarily, contraction in cerebral vessels via PCP or sigma-opiate receptors: and cerebral vascular muscle may provide a useful tool to analyse the molecular constitution of these two distinct and opposite-acting opiate receptors.

Religious and mystical experiences as artifacts of temporal lobe function: a general hypothesis

Mystical and religious experiences are hypothesized to be evoked by transient, electrical microseizures within deep structures of the temporal lobe. Although experiential details are affected by context and reinforcement history, basic themes reflect the inclusion of different amygdaloid-hippocampal structures and adjacent cortices. Whereas the unusual electrical coherence allows access to infantile memories of parents, a source of good expectations, specific stimulation evokes out-of-body experiences, space-time distortions, intense meaningfulness, and dreamy scenes. The species-specific similarities in temporal lobe properties enhance the homogeneity of cross-cultural experiences. They exist along a continuum that ranges from "early morning highs" to recurrent bouts of conversion and dominating religiosity. Predisposing factors include any biochemical or genetic factors that produce temporal lobe lability. A variety of precipitating stimuli provoke these experiences, but personal (life) crises and death bed conditions are optimal. These temporal lobe microseizures can be learned as responses to existential trauma because stimulation is of powerful intrinsic reward regions and reduction of death anxiety occurs. The implications of these transients as potent modifiers of human behavior are considered.

Pharmacologic inhibition of cerebral vasospasm in ischemia, hallucinogen ingestion, and hypomagnesemia: barbiturates, calcium antagonists, and magnesium

Experiments indicate that several different calcium antagonists have vasodilatory properties which may be expressed selectively on different organ vascular beds. Verapamil was most active as a vasodilator in muscular microvasculature. Cerebral venules are most sensitive to nimodipine. Nisoldipine is inactive in cerebral vascular dilation. We have also studied the vasodilatory effects of several barbiturates. Pentobarbital is the most active cerebrovasodilator in this class of anesthetics. This agent inhibits the vasospastic activity of potassium, serotonin, and prostaglandins, and appears to be a calcium entry antagonist in vasculature. The hallucinogens phencyclidine, mescaline, and LSD all induce cerebral vasospasm. This can be either blocked or reversed with calcium antagonists. Magnesium is a competitive calcium antagonist, and alterations in the extracellular content of this ion have profound effects on cerebral vascular resistance.

Alcohol-induced spasms of cerebral blood vessels: relation to cerebrovascular accidents and sudden death

Ethyl alcohol produced graded contractile responses in rat cerebral arterioles and venules in vivo and in isolated canine basilar and middle cerebral arteries at a concentration range (10 to 500 milligrams per deciliter) which parallels that needed for its graded effects of euphoria, mental haziness, muscular incoordination, stupor, and coma in humans. Two specific calcium antagonists, nimodipine and verapamil, prevented or reversed the alcohol-induced cerebrovasospasm and thus may prove valuable in treating the hypertension and stroke observed in heavy users of alcohol.

Phencyclidine ("angel dust") analogs and sigma opiate benzomorphans cause cerebral arterial spasm

Several psychotomimetic phencyclidine (PCP) analogs--N-ethyl-l-phenylcyclohexylamine (PCE), N-[1-(2-thienyl)cyclohexyl]piperidine (TCP), N-[1-(thienyl)cyclohexyl ))pyrrolidine (THP), ketamine, and N,N-dimethyl-l-phenyl-cyclohexylamine (PCDEA)--were tested on basilar and middle cerebral arteries of the dog in vitro and found to induce contraction in these blood vessels with a maximal contractile activity (i.e., intrinsic activity) similar to that of PCP. The concentration-effect curves of these compounds were found to be parallel to the curve of PCP (P less than 0.01). The relative potency was PCE greater than TCP greater than PCP greater than THP greater than PCDEA greater than ketamine. A PCP analog with no psychotomimetic activity, 1-piperidinocyclohexanecarbonitrile (PCC), did not induce the blood vessels to contract, nor did the opiate morphine. Three psychotomimetic benzomorphans--pentazocine, cyclazocine, and N-allylnorcyclazocine--were found to: (i) also produce contraction; and (ii) have concentration--effect curves parallel to the curve of PCP, but with reduced intrinsic activities (i.e., maximal tensions were lowered) compared to PCP. A kappa opiate, ethylketocyclazocine, relaxed the blood vessels in a dose-dependent manner. This study provides direct evidence for a distinct PCP receptor on cerebral blood vessels and suggests that certain benzomorphans may produce cerebral vasospasm via PCP-receptor interactions.

The influence of nisoldipine--a "calcium entry blocker" on drug induced stereotyped behavior in rats

In view of potential ability of calcium entry blockers to affect Ca2+ fluxes in neurons, the effects of nisoldipine on phencyclidine (PCP) and apomorphine (APO) induced stereotyped behavior have been examined in 3 and 4 week old rats. The rats (3 and 4 weeks old) were pretreated with either 0.2 ml of saline + ethanol mixture (10:1 v/v) or nisoldipine (25 mg/kg) i.p., 5 min before the i.p. administration of PCP (5 mg/kg) or APO (10 mg/kg). While nisoldipine pretreatment significantly blocked the PCP induced stereotypy in 3 and 4 week old rats, the APO induced stereotypy was not altered. These preliminary data suggest that nisoldipine specifically blocks PCP induced stereotypy probably by antagonizing it effects at the presynaptic level. The significance of this finding in relation to mechanism of action of PCP and calcium entry blockers is discussed.

Effect of phencyclidines on hippocampal pyramidal cells

Phencyclidine (PCP) and several behaviorally active or inactive structural analogs were administered i.v. to urethane-anesthetized rats in order to determine their effects on CA1 pyramidal cell discharges elicited by contralateral CA3 (cCA3) stimulation. PCP and the behaviorally active m-amino derivative (m-NH2 PCP) depressed, in a dose-dependent manner, the amplitude of the population spike evoked in CA1 by a cCA3 stimulation (ED 50s: 0.9 mg/kg for PCP, 0.5 mg/kg for m-NH2 PCP). However, the behaviorally inactive derivatives m-nitro (m-NO2 PCP) and PCP methyliodide (PCP CH3I) were ineffective up to 10 mg/kg. PCP (0.1-0.3 mg/kg i.v.) also decreased the duration of inhibition of CA1 discharges in a paired-stimulus paradigm; this was in contrast to the effects of thiopental and diazepam. In midcollicular-transected, urethane-anesthetized rats, the inhibitory effect of PCP on cCA3-CA1 transmission was not observed but the drug was still as effective as in intact rats in the paired-stimulus paradigm. In animals subjected to 6-hydroxydopamine lesions of the hippocampal noradrenergic innervation (average 85%) decrease in NE content), the potency of PCP in inhibiting cCA3-CA1 transmission was the same as in a group of sham-operated controls. These results suggest the following conclusions: (i) PCP exerts at least 2 separate types of effects in CA1, both of which result from a central action of the drug; (ii) PCP decreases the monosynaptic excitation of CA1 pyramidal cells and this action requires the integrity of brainstem afferents; (iii) PCP may decrease recurrent inhibition or afterhyperpolarization in CA1 via a mechanism which is independent of these connections and, therefore, could result from a direct action of the drug at the level of the hippocampus; (iv) finally, no evidence was found to suggest that the noradrenergic innervation of the hippocampus is critically involved in the action of PCP on CA1 discharges.