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

Perivascular expression and potent vasoconstrictor effect of dynorphin A in cerebral arteries

Background

Numerous literary data indicate that dynorphin A (DYN-A) has a significant impact on cerebral circulation, especially under pathophysiological conditions, but its potential direct influence on the tone of cerebral vessels is obscure. The aim of the present study was threefold: 1) to clarify if DYN-A is present in cerebral vessels, 2) to determine if it exerts any direct effect on cerebrovascular tone, and if so, 3) to analyze the role of κ-opiate receptors in mediating the effect.

Methodology/Principal Findings

Immunohistochemical analysis revealed the expression of DYN-A in perivascular nerves of rat pial arteries as well as in both rat and human intraparenchymal vessels of the cerebral cortex. In isolated rat basilar and middle cerebral arteries (BAs and MCAs) DYN-A (1–13) and DYN-A (1–17) but not DYN-A (1–8) or dynorphin B (DYN-B) induced strong vasoconstriction in micromolar concentrations. The maximal effects, compared to a reference contraction induced by 124 mM K⁺, were 115±6% and 104±10% in BAs and 113±3% and 125±9% in MCAs for 10 µM of DYN-A (1–13) and DYN-A (1–17), respectively. The vasoconstrictor effects of DYN-A (1–13) could be inhibited but not abolished by both the κ-opiate receptor antagonist nor-Binaltorphimine dihydrochloride (NORBI) and blockade of G_i/o-protein mediated signaling by pertussis toxin. Finally, des-Tyr¹ DYN-A (2–13), which reportedly fails to activate κ-opiate receptors, induced vasoconstriction of 45±11% in BAs and 50±5% in MCAs at 10 µM, which effects were resistant to NORBI.

Conclusion/Significance

DYN-A is present in rat and human cerebral perivascular nerves and induces sustained contraction of rat cerebral arteries. This vasoconstrictor effect is only partly mediated by κ-opiate receptors and heterotrimeric G_i/o-proteins. To our knowledge our present findings are the first to indicate that DYN-A has a direct cerebral vasoconstrictor effect and that a dynorphin-induced vascular action may be, at least in part, independent of κ-opiate receptors.

The Effects of Opioid Peptides on Cardiovascular Function and Sympathetic Neurotransmission in Rats

The haemodynamic effects of three opioid receptor agonists, with some preferential activity on δ-, μ- and κ-receptors were investigated in anaesthetized and pithed rats, and effects on sympathetic neurotransmission were also investigated in pithed rats.

In anaesthetized rats, d-Ala2-d-Leu5-enkephalin (DADLE) (a predominantly δ-receptor agonist, 10 μg kg−1), glyol (μ, 0·5 mg kg−1) and R,S-N-C2-N-methyl-3,4,dichloro-phenylacetamido-2-C3-carboxy phenylethyl-pyrrolidine (ICI 204448) (·, 0·1 mg kg−1) by intravenous administration transiently decreased heart rate from 462 ± 12 to 432 ± 14, 460 ± 12 to 448 ± 13 and 460 ± 12 to 448 ± 11 beats min−1, respectively, and mean arterial blood pressure from 142 ± 6 to 111 ± 9, 141 ± 6 to 122 ± 5 and 148 ± 7 to 121 ± 6 mmHg, respectively. The effects of DADLE, but not those of glyol or ICI 204448, were blocked by M8008, a δ-receptor antagonist. In pithed rats, none of the opioid agonists had any significant effects on heart rate or mean arterial blood pressure; however, acetylcholine significantly reduced both heart rate and mean arterial blood pressure. All three opioid agonists reduced the positive chronotropic response to thoracic (C7-T2) spinal cord stimulation in pithed rats, by 17 ± 4,30 ± 2 and 20 ± 10% for DADLE, glyol and ICI 204448, respectively. This compared with a 48 ± 15% reduction with clonidine (5 μ kg−1). This effect of DADLE was almost abolished by M8008.

It is concluded that the haemodynamic effects of the opioid agonists studied are mediated via actions on the central nervous system and that a decrease in sympathetic neurotransmission may account for, at least in part, the bradycardia produced by opioid agonists in intact anaesthetized rats. It seems that the sympathetic nervous system is unlikely to be involved in the arrhythmogenic effects of opioid peptides.

Critical care sedation for neuroscience patients

In 2000, the Joint Commission on Accreditation of Healthcare Organizations (JCAHO) introduced the mandate for the implementation of standards for both pain assessment and need for therapy in hospitalized patients. The need for the appropriate titration of sedation and analgesia is particularly poignant in an intensive care unit (ICU) setting where iatrogenic discomfort often complicates patient management. Neurologically ill patients in ICUs present particularly complex sedation issues, owing to the need to monitor these patients with serial neurological exams. Hence, maximal comfort without diminishing neurological responsiveness is desirable. Here, we review the frequently applied methods of evaluating levels of pain and agitation in critically ill patients as well as discuss the appropriate classes of pharmaceutical agents common to this population, with particular emphasis on the potential neurophysiological impact of such therapy.

The diverse molecular mechanisms responsible for the actions of opioids on the cardiovascular system

The actions of opioid agonist and antagonist drugs have not been well characterized in the heart and cardiovascular system. This stems from the limited role opioid receptors have been perceived to have in the regulation of the cardiovascular system. Instead, the focus of opioid receptor research, for many years, relates to the characterization of the actions of opioid drugs in analgesia associated with receptor activation in the CNS. However, recent studies suggest that opioid receptors have a role in the heart and cardiovascular system. While some of these actions may be mediated by activation of peripheral opioid receptors, others are not, and may result from direct or receptor-independent actions on cardiac tissue and the peripheral vascular system. This review will outline some of the diverse molecular mechanisms that may be responsible for the cardiovascular actions of opioids, and will characterize the role opioid receptors have in several cardiovascular pathophysiological disease states, including hypertension, heart failure, and ischaemic arrhythmogenesis. In many instances, it would appear that the effects of opioid agonists (and antagonists) in cardiovascular disease models may be mediated by opioid receptor-independent actions of these drugs.

Peptides as neurotransmitters in vascular autonomic neurons

1. Neuropeptides are present in the majority of autonomic neurons projecting to blood vessels, where they are co-localized with non-peptide transmitters and sometimes with other peptides. 2. Neuropeptides are released from vasoconstrictor and vasodilator nerve terminals after high frequency stimulation ( > 2-5Hz) with trains of impulses. 3. Neuropeptides can have potent post-synaptic effects on vascular tone, but often these effects are restricted to selected regions of the vasculature. 4. Post-synaptic effects of neuropeptides tend to be more slowly-developing and more long-lasting than those of non-peptide transmitters. 5. Autonomic vasoconstrictor and vasodilator responses often have multiple phases, with the faster phases being mediated by non-peptide transmitters and the slower phases medicated predominantly by one or more neuropeptides. 6. Some neuropeptides do not seem to have post-synaptic effects in a particular vascular bed, but can have presynaptic actions on neurotransmitter release. 7. Neuropeptides form an important component of the repertoire of neurotransmitters used by vascular autonomic neurons to regulate regional blood flow in response to a range of physiological stimuli.

mu- and delta-opioid receptor-mediated contractile effects on rat aortic vascular smooth muscle

The actions of opioid receptor agonists and antagonists were studied in isolated rat aortic strips. Morphine (10(-7)-10(-6) M) had no contractile effect on resting strips but when added during the relaxation of the contractions induced by 10(-9) M noradrenaline, it induced a contractile response which was blocked by naloxone. The selective mu-opioid receptor agonist, [D-Ala2,N-Me-Phe4,Gly5-ol]enkephalin (DAMGO, 10(-7)-10(-6) M), induced an increase in basal tension which remained after removal of endothelium or in Ca(2+)-free solution, but was inhibited by beta-flunaltrexamine. beta-Flunaltrexamine also inhibited the contractile response induced by DAMGO added during the relaxation of the contractions induced by noradrenaline. The delta-opioid receptor agonist, [D-Pen2,D-Pen5]enkephalin, had no effect on resting tension but potentiated the contractions induced by noradrenaline; these effects were abolished by naltrindol. The selective kappa-opioid receptor agonist, bremazocine, had no effect on resting tension and did not modify the amplitude of the contractions induced by noradrenaline. These results suggest that, at low concentrations, agonists of mu- and delta-opioid receptors may act as modulators of noradrenaline-induced responses, whereas at higher concentrations, mu-opioid receptor stimulation may have a direct contractile effect in isolated rat aorta.

Central analgesic mechanisms: a review of opioid receptor physiopharmacology and related antinociceptive systems

Clinical applications of these principles, based on the increased understanding of central analgetic mechanisms, are already being undertaken. Not only does the use of intrathecal and epidural opioids have the potential to decrease pain and related morbidity after surgical procedures, but there is at least one study that demonstrates a significant reduction in both major morbidity and mortality in high-risk surgical patients in whom epidural anesthesia and analgesia were used. These principles are also useful for the management of patients undergoing cardiac surgery. Currently, high-dose narcotic anesthesia is the technique of choice for such patients because of the greater hemodynamic stability this anesthetic technique provides. However, breakthrough hypertension and tachycardia still occur, and prolonged postoperative ventilation is a necessary consequence due to the high doses of narcotics that are required. In one study of patients undergoing coronary artery surgery, preoperative administration of clonidine, 5 micrograms/kg, orally, was demonstrated to decrease fentanyl requirements by 45% (110 to 61 micrograms/kg) while producing a similar degree of hemodynamic stability as seen with high-dose fentanyl. Extubation times were not compared, but the significantly lower dosage of fentanyl in the clonidine-treated group would be expected to lead to an earlier extubation. Whether similar potentiation of narcotic effects would be seen with dexmedetomidine, which may also prevent narcotic-induced rigidity, has not been determined, but the clinical application of such synergistic and complementary agents is another consequence of the greater understanding of central analgesic mechanisms, and augurs well for the future.

Opioid inhibition of nicotine-induced 45Ca2(+)-uptake into cultured bovine adrenal medullary cells

The ability of a number of opioid agonists and antagonists to affect nicotine-induced 45Ca2(+)-uptake into cultured bovine adrenal medullary cells has been investigated. High (10 microM) concentrations of the opioid agonist bremazocine produced a significant inhibition of nicotine-induced 45Ca2(+)-uptake throughout the 15 min time course examined. The opioid subtype-selectivity of this inhibition was investigated; mu and delta selective agonists produced only minor effects whereas the kappa selective agonist U50-488H and the endogenous opioid peptides dynorphin(1-13) and metorphamide almost abolished nicotine-induced 45Ca2(+)-uptake. The U50-488H inhibition was significant at 10 nM concentrations with an IC50 of approximately 1 microM. U50-488H inhibition could not be reversed or reduced by the opioid antagonists naxolone, diprenophine or Mr2266. Furthermore, Mr2266 and its optical isomer Mr2267 also produced marked inhibition of 45Ca2(+)-uptake. The inhibition was specific to nicotine-induced 45Ca2(+)-uptake in that a similar level of uptake evoked by potassium depolarization was unaffected by high concentrations of U50-488H. These data indicate that opioid inhibition of nicotine-induced 45Ca2(+)-uptake does not involve classical, stereospecific opioid receptors and suggests the involvement of a pharmacologically distinct opioid recognition site. It is speculated that this may be associated with the nicotine receptor-ionophore complex.

Inhibition of sympathetic neurotransmission by the opioid delta-receptor agonist DAMA in the pithed rat

1. The effects of [D-Ala2,Met5]enkephalinamide (DAMA), an analogue of [Met5]-enkephalin that acts selectively on opioid receptors of the delta-subtype, were studied on pressor responses elicited by sympathetic stimulation in pithed rats. 2. Intravenous injections of bolus doses of 0.1 mg/kg and 0.3 mg/kg of DAMA did not affect either the basal blood pressure or pressor responses to noradrenaline. 3. Pressor responses elicited either by electrical stimulation of the spinal sympathetic outflow or by stimulation of sympathetic ganglion cells with the muscarinic agonist McN-A-343 were reduced by DAMA. 4. Naloxone (1 mg/kg + 0.5 mg/kg per h) had no significant effect on the basal blood pressure or on pressor responses to spinal sympathetic stimulation, but antagonised the inhibitory effect of DAMA. 5. These results indicate that activation of opioid delta-receptors on sympathetic vasomotor nerve terminals can inhibit noradrenergic neurotransmission.

Effect of kappa-opioid receptor agonists on morphine analgesia in morphine-naive and morphine-tolerant rats

The effect of i.p. administration of kappa-opioid receptor agonists, bremazocine, tifluadom and U-50,488H on morphine (8 mg/kg i.p.)-induced analgesia in morphine-naive and morphine tolerant male Sprague-Dawley rats was determined using the tail-flick test. The tolerance to morphine in the rats was induced by s.c., implantation of six morphine pellets during a 7-day period. Implantation of morphine pellets resulted in the development of tolerance as evidenced by the decrease in the analgesic response to morphine when compared to placebo pellets implanted rats. Bremazocine (0.3, 1.0 and 3.0 mg/kg) and U-50,488H (16 mg/kg) antagonized morphine-induced analgesia in morphine-naive rats while tifluadom (8 and 16 mg/kg) potentiated the effect. In morphine-tolerant rats, bremazocine (3 mg/kg) and U-50,488H (16 mg/kg) potentiated morphine-induced analgesia. Tifluadom at any of the doses had no effect on morphine-induced analgesia in morphine-tolerant rats. These results provide evidence that different kappa-opioid agonists modify morphine-induced analgesia differentially in morphine-naive and morphine-tolerant rats.

Is ascites caused by impaired hepatic inactivation of blood borne endogenous opioid peptides?

Methionine enkephalin and catecholamines were measured in carefully collected plasma samples from 25 patients with cirrhosis and ascites, and 25 with cirrhosis without ascites, 15 disease and 15 healthy controls. Methionine enkephalin was invariably raised in the ascites group, the median value being 4.6-6.9 times that of the other three groups. Similarly, in the ascites group, median noradrenaline was increased 2.5-4.2 and median adrenaline 1.8-2.5 times that of the other groups. Plasma methionine enkephalin is considerably raised in patients with cirrhotic ascites and has actions which could enable it to be an initiating factor of ascites formation.

Peripheral sympatho-inhibitory cardiovascular effects of opioid peptides in anaesthetized rabbits

1. Opioid agonists influence isolated cardiovascular tissues from rabbits, as well as the cardiovascular system of pithed rabbits, through presynaptic receptors on postganglionic sympathetic nerve fibres. The present experiments were carried out in order to study effects which result from activation of these receptors in anaesthetized rabbits. 2. In pithed rabbits with electrically stimulated sympathetic outflow, infusion of [D-Ala2-D-Leu5]-enkephalin (DADLE) 10 micrograms kg-1 min-1 and dynorphin-(1-13) (dynorphin) 1 microgram kg-1 min-1 decreased the plasma noradrenaline concentration, mean arterial pressure (MAP) and heart rate. The effects of dynorphin and, less completely, those of DADLE were antagonized by the peripherally selective opioid antagonists N-methyl naloxone bromide (NMN) 1.3 mg kg-1 and N-methyl levallorphan methanesulphonate (NML) 1-3 mg kg-1. 3. In pentobarbitone-anaesthetized rabbits, DADLE 3-30 micrograms kg-1 min-1 and dynorphin 0.3-3 micrograms kg-1 min-1 decreased the plasma noradrenaline concentration and MAP. The highest dose of dynorphin also decreased heart rate, whereas DADLE 10 micrograms kg-1 min-1 caused slight cardioacceleration. The effects of DADLE but not those of dynorphin decreased upon repeated administration. 4. The effects of dynorphin 10 micrograms kg-1 min-1 were abolished or greatly attenuated by NMN 1.3 mg kg-1 and NML 3 mg kg-1. In contrast, the antagonists reduced only slightly the blood pressure-lowering effect of DADLE 10 micrograms kg-1 min-1 and did not reduce significantly the effects of DADLE on the plasma noradrenaline level and heart rate. 5. It was concluded that systemically administered dynorphin produces sympatho-inhibition and an ensuing fall in blood pressure by an action at peripheral receptors, in all probability presynaptic Kappa-receptors on postganglionic sympathetic nerve fibres. The effects of DADLE are more complex and may involve both central and peripheral components.

Presynaptic opioid delta-receptors in the rabbit mesenteric artery

Excitatory junction potentials (e.j.p.s) evoked by nerve stimulation were recorded from muscle cells of the rabbit isolated mesenteric artery. At 0.03 Hz the e.j.p. amplitudes were stable. When a train of fifteen pulses was applied at 0.25 Hz or at higher frequencies (0.5, 1 and 2 Hz), e.j.p.s showed an initial facilitation followed by depression. [Met5]enkephalin 0.1 and 1 mumol/l, [D-Ala2,D-Leu5]enkephalin 0.1 and 1, but not 0.01 mumol/l, and [D-Pen2, L-Pen5]enkephalin 3 mumol/l all depressed the e.j.p.s evoked by trains of fifteen pulses at 1 Hz. When more than one concentration was used ([Met5]enkephalin, [D-Ala2,D-Leu5]enkephalin), the inhibition was concentration dependent. It was always greater for the first few e.j.p.s than for the later ones in a train. [Met5]enkephalin 1 mumol/l reduced the first e.j.p. at 1 Hz and the e.j.p.s evoked by 0.03 Hz to a similar extent. The inhibitory effect of [Met5]enkephalin 1 mumol/l on e.j.p.s persisted in the presence of yohimbine 0.3 mumol/l. Naloxone 1 mumol/l did not interfere with the effect of [Met5]enkephalin 1 mumol/l. Naloxone 10 mumol/l depressed some e.j.p.s and prevented the inhibition by [Met5]enkephalin 1 mumol/l. Neither ICI 154129 10 mumol/l nor ICI 174864 0.3 mumol/l had any effect of their own and both compounds antagonized the action of [Met5]enkephalin 1 mumol/l. Normorphine 10 mumol/l, fentanyl 1 mumol/l, ethylketocyclazocine 0.1 mumol/l, and dynorphin A(1-13) 1 mumol/l were all ineffective. Ethylketocyclazocine 1 mumol/l did not change the e.j.p.s either, but antagonized [Met5]enkephalin 1 mumol/l. [Met5]enkephalin 1 mumol/l failed to influence both the resting membrane potential of the muscle cells and the depolarizing effect of noradrenaline 3 and 30 mumol/l. We suggest that the axon terminals of post-ganglionic sympathetic neurones in the rabbit mesenteric artery possess opioid delta-, but not mu- or kappa-receptors. The activation of presynaptic delta-receptors inhibits the release of the neuroeffector transmitter. There is no evidence for any effect of co-released endogenous opioid peptides under our experimental conditions.

Effects of kappa opiate agonists on neurochemical and neuroendocrine indices: evidence for kappa receptor subtypes

Four kappa opiate agonists, U-50488H, MR-2034, EKC and tifluadom, elevated plasma corticosterone and decreased plasma TSH in a dose-dependent manner. These effects were naloxone-reversible. However, WIN 44441-3, a long acting narcotic antagonist, was unable to reverse the effects of U-50488H and MR-2034 upto doses of 5 mg/kg. U-50488H and MR-2034 but not tifluadom or EKC, also increased levels of DOPAC and HVA in the olfactory tubercle. This effect was also naloxone-reversible but not WIN 44441-3 reversible. Tifluadom and EKC did not increase DOPAC and HVA. The differential responses of the tested kappa agonists to WIN 44441-3 antagonism and dopamine metabolism in A10 neurons suggest that the kappa agonists can be separated into two groups. This is the first physiological evidence suggestive of kappa opioid receptor subtypes.

Effects of enkephalins, morphine, and naloxone on pial arteries during perivascular microapplication

The effects of the opiate receptor agonists, enkephalins and morphine, and the antagonist, naloxone, on cerebrovascular resistance vessels was investigated in situ by employing perivascular microapplication. Feline pial arteries with a resting diameter of 66-294 micron were tested. Vascular diameter was measured using television image splitting. Concentration-response curves revealed no change of diameter when Leu-enkephalin, D-Ala2-Leu-enkephalinamide, D-Ala2-Met-enkephalinamide, and morphine were applied in concentrations of 10(-11)-10(-5) M. Considering the concentrations of enkephalins that have been found in natural cerebrospinal fluid or that can be expected in the vicinity of enkephalinergic synapses, the data obtained with the lower concentrations indicate that enkephalins are probably not important for the regulation of pial arterial resistance. At 10(-4) M only the dilation (4.3%) elicited by D-Ala2-Leu-enkephalinamide was statistically significant (p less than 0.01). All four agonists at 10(-3) M induced significant dilatations varying between 5.4 and 13.6%. Naloxone exerted no vascular effect per se at 10(-5) and 10(-4) M but a dilatation of 15.3% at 10(-3) M. The latter can be explained by a partial agonist action. During simultaneous administration, naloxone (10(-4) M) reduced the dilatations induced by 10(-4) and 10(-3) M D-Ala2-Leu-enkephalinamide dose dependently. This indicates that mu- and delta-opioid receptors, probably located at the vascular smooth muscle cell, were involved in the mediation of the dilatation induced by the highest concentrations of the compounds.

Proenkephalin- and prodynorphin- derived opioid peptides in guinea-pig heart

Consecutive high performance liquid chromatography (HPLC) fractionation and the mouse vas deferens assay were used to characterize opioid peptides in the guinea-pig heart. Atria were found to contain at least nine different opioid peptides derived from proenkephalin and prodynorphin. In ventricles at least seven different molecular species which may be derived only from prodynorphin were present. The total opioid activity in atria averaged 22 pmol and in ventricles 11 pmol [Met]enkephalin equivalents per g wet wt. The high content of [Leu]enkephalin in relation to [Met]enkephalin indicates the possibility of a dynorphinergic pathway of cardiac [Leu]enkephalin. Multiple cardiac opioid ligands and receptors, including kappa, may be functionally important in the peripheral control of cardiac performance and coronary circulation.

Behavioural and spectrum power effects of opioid peptides in chicks

The effects of intracerebroventricular administration of beta-endorphin, dermorphin, D-ala2-methionine-enkephalinamide (DALA) and pentazocine, on behaviour, electrocortical activity and ECoG spectrum power in young chicks were studied. Beta-endorphin, dermorphin and DALA produced dose-dependent behavioural sedation and sleep accompanied by electrocortical high voltage slow wave activity and increase in total voltage power with a predominant increase in the lower bands of ECoG spectrum. Dermorphin was found significantly more potent than beta-endorphin and DALA since it was active at much lower doses. Behavioural and ECoG sleep evoked by opioid peptides were rapidly reversed by naloxone showing that these effects are mediated through an activation of specific opioid receptors. Doses of pentazocine equimolar with doses of dermorphin and beta-endorphin producing sleep did not affect behaviour and spectrum power whereas higher doses produced opposite effects, i.e., behavioural stimulation, pecking and increase in locomotor activity.

Ethylketocyclazocine decreases noradrenaline release and blood pressure in the rabbit at a peripheral opioid receptor

Rabbits were pithed and their sympathetic outflow was stimulated electrically via the pithing rod. Arterial blood pressure, heart rate, the endogenous plasma noradrenaline level, the plasma 3H-noradrenaline clearance and the noradrenaline release rate (the rate of entry of endogenous noradrenaline into the plasma) were determined. Ethylketocyclazocine 0.1 mg kg-1 + 0.02 mg kg-1 h-1 and 1 mg kg-1 + 0.2 mg kg-1 h-1 but not 0.01 mg kg-1 + 0.002 mg kg-1 h-1 decreased blood pressure, the endogenous plasma noradrenaline level and the noradrenaline release rate. The effects of ethylketocyclazocine 1 mg kg-1 + 0.2 mg kg-1 h-1 were antagonized by naloxone 1 mg kg-1 + 0.5 mg kg-1 h-1. Given alone, naloxone caused no change. It is concluded that ethylketocyclazocine inhibits action potential-evoked release of noradrenaline from postganglionic sympathetic neurones, and hence can lower blood pressure, by a peripheral effect, possibly mediated by opioid receptors at the terminal axons.

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.