Ocular and systemic responses to water soluble material derived from Cannabis sativa (marihuana)

Marijuana-derived material-induced changes in monkey ciliary processes differ from those in rabbit ciliary processes

The morphologic changes in ciliary processes and the associated intraocular pressure (IOP) were observed in owl and squirrel monkeys after intravitreal (IVT) and intravenous (IV) injections of water soluble marijuana-derived material (MDM). The response in monkeys differed from that reported in rabbits wherein IV injection induced severe ciliary swelling and a significant decrease in IOP. Only moderate swelling occurs in monkey processes after IV injection of relatively high dose of MDM, and this change, which includes disruption of the basal lamina of the pigment epithelium, is not associated with a change in IOP. Severe swelling occurs in the crests of monkey ciliary processes after IVT injection, which is accompanied by a fall in IOP. The difference in the response in monkey versus rabbit ciliary processes after IV injection of MDM may be due to a more compact stroma in the monkey processes.

Centripetal movement of fluorescein dextrans in the cornea: relevance to arcus

The centripetal movement of fluorescein and fluorescein-labelled dextrans (4 to 150 kD) from sclera or cut edge of the cornea was determined in isolated rabbit corneas at 4 and 24 h. Corneas were divided into 5.5 mm diameter central core, inner 5.5 to 8 mm donut, 8 to 12 mm peripheral donut and, where applicable, scleral rim. For all molecules greater than sodium fluorescein (376 D) tracer concentrations in the 5.5 mm core and the 5.5 to 8 mm donut were equal. Without sclera rim, the more central portions of the cornea (5.5 mm core and 5.5 to 8 mm donut) had tracer concentrations equal to those of corneas-with-sclera for all tracers greater than 10 kD. The tracer concentrations in the central cornea were the same in the presence or absence of sclera. The data indicate a physiological barrier to the lateral diffusion of molecules greater than 10 kD between the peripheral and more central cornea.

Water soluble high molecular weight components from plants with potent intraocular pressure lowering activity [corrected and republished ariticle originally printed in Curr Eye Res 1987 May;6(5):733-4]

Previous work in our laboratory has shown that Cannabis sativa (marijuana) contains water-soluble, high molecular weight components that have extremely potent intraocular pressure (IOP) lowering activity. Aqueous extraction of other plants has now shown that a number of them also contain components with potent IOP lowering activity in rabbits. These include tobacco, cabbage, lettuce, several greens, Senecio anonymus, Erigeron philadelphicus, and several others. Not all plants tested were active, however, indicating that while more ubiquitous than originally thought, these materials are not apparently extractable from all plants. The chemical composition of the active fraction from tobacco was found to be different from that derived from Cannabis sativa.

Prostaglandin involvement in the responses of the rabbit eye to water-soluble marihuana-derived material

Both anticoagulants (heparin and streptokinase) and non-steroidal anti-inflammatory compounds (aspirin and indomethacin) were used against a water-soluble derivative of marihuana, MDM. While the anticoagulants had no effect on the ocular effects of MDM, both aspirin and indomethacin altered the time course and effected the MDM-induced reduction of intraocular pressure. The usual initial hypertensive effect of intravenous MDM was eliminated and the later intraocular pressure fall occurred earlier as well as being inhibited by about 35 to 50%. Assay for prostaglandins revealed that intravenous MDM (3.86 micrograms) caused a marked rise in PGE2 concentration of the aqueous humor and iris-ciliary body during the first hour or two after administration of MDM, but normal values occurred at 4, 6, and 8 hours when the intraocular pressure is reduced by up to 60%. Following intravitreal MDM (0.002 microgram), however, the PGE2 levels remained unchanged over 24 hours, despite the induction of a fall in intraocular pressure between 14 and 18 hours which lasts for many hours. Prostaglandin appears to be involved in the hypertensive phase of intraocular pressure change after intravenous MDM injection; and, while the fall in intraocular pressure may contain a component partially mediated by prostaglandins, there is no evidence that intravitreal MDM induces any effect on prostaglandin levels. The involvement of prostaglandins, therefore, in the mediation of MDM-induced ocular hypotensive effects is apparently small.

Effects of water-soluble marihuana-derived material (MDM) on the rabbit ciliary body: light and electron microscopy

The response of the ciliary processes of the rabbit eye to water-soluble marihuana-derived material (MDM) has been examined with light and electron microscopy. Following intravenous injection of MDM, the processes undergo considerable swelling within 1 hour followed by thrombus formation in the capillaries and extravasation of red cells. Later phases include the formation of cysts between the non-pigmented and pigmented cell layers of the ciliary epithelium. The ciliary process edema coincides with the initial hypertensive phase seen after intravenous MDM, while the hematogenous response coincides with the fall in intraocular pressure. Following intravitreal injection of MDM, a similar pattern of structural changes occurs that accompanies a fall in intraocular pressure that lasts for several days; because the physiological response occurs over a longer time course (14-20 hours) relative to intravenous administration where the intraocular pressure changes occur rapidly, the ciliary process swelling phase does not result in an increase in intraocular pressure. The physiologic changes in the eye caused by MDM appear to be related to the induction of a general inflammatory response in the ciliary processes, with a primary effect on the vascular system.

Intraocular pressure and aqueous humor dynamics in rabbit and primate with d- and 1-adrenergic compounds

The effects of the d- and 1-isomers of epinephrine and norepinephrine have been determined on intraocular pressure (IOP) in conscious rabbits and rhesus monkeys, and on aqueous humor turnover rate (AHTR) in rabbits. Relatively specific beta-adrenergic antagonists (butoxamine and metoprolol) were used to attempt to modify the responses. The effects on IOP in both species are similar to those of racemic mixtures. The d- and 1-isomers of norepinephrine and epinephrine reduced IOP, and reduced AHTR in rabbits. The d- and 1-isomers of norepinephrine had little effect on IOP in monkeys while d- and 1-epinephrine increased IOP. Metoprolol, a beta 1-antagonist was more effective than butoxamine (beta 2-antagonist) at modifying the effect of the norepinephrine isomers in rabbits.

Marihuana-derived material: biochemical studies of the ocular responses

Some biochemical factors of the iris-ciliary body of the rabbit have been examined for effects induced by water-soluble marihuana-derived material (MDM). Adenylate cyclase activity and sensitivity to beta-adrenergic agonists were unchanged, as measured 4 hours after MDM administration in vivo. Magnesium-dependent and anion-sensitive, but not sodium-potassium, ATPase activities were inhibited 6 hours after MDM administration in vivo, although they were unaffected by in vitro incubation. Topical administration of a potent substance P antagonist had no effect on the time course or magnitude of intravenous MDM-induced ocular effects in rabbit. Intravenously administered sugars antagonized the effects of MDM on intraocular pressure. A variety of drugs which display a range of biochemical effects varying from beta-adrenergic receptor agonism, to alteration of glycoprotein residues were employed. None of the agents employed, ranging from cAMP modifiers to protein synthesis blockers, had any effect on the MDM-induced response. It is apparent that the mechanism underlying the ocular hypotensive effect of MDM does not reside in mediation through adenylate cyclase, ATPase or substance P, but rather through a mechanism mediated by terminal sugar moieties on the molecule. The data suggest that modification of the surface membrane glycoprotein residues on the ciliary epithelium can induce marked alterations in aqueous humor flow rate.

Ocular fluid dynamics response to topical RU486, a steroid blocker

A steroid antagonist applied to one eye of 18 young pigmented rabbits during a 10-week period caused a statistically significant fall in IOP, but no statistically significant nor clinically relevant change in the rate of aqueous humor turnover. The pressure change is therefore ascribed to an alteration in outflow channels. No changes occurred in a parallel group of 5 animals in which one eye was treated with vehicle and the contralateral eye was untreated. The drug effects became evident after two weeks of application, suggesting that a slow turnover pathway is involved.

A synopsis of recent developments in antiglaucoma drugs

Open-angle glaucoma is treated primarily with drugs, some of which have been used clinically for years. These drugs include: 1) cholinergic agonists that increase aqueous humor outflow, 2) adrenergic agonists and antagonist that affect both aqueous humor formation and outflow, and 3) carbonic anhydrase inhibitors that decrease aqueous humor formation. Several new classes of drugs are being tested for efficacy and mechanism of action. They include: 1) the D-isomer of timolol that reduces aqueous humor formation without producing adrenergic blockade, 2) dopaminergic agonists and antagonists, including bromocriptine and butyrophenones that reduce intraocular pressure, and 3) cannabinoids that reduce aqueous humor formation and increase outflow. In addition, several other types of drugs, such as prostaglandins, diuretics, Na+,K+-ATPase inhibitors, and adenyl cyclase stimulators are just now beginning to be studied.

Cellular mechanisms in the actions of antiglaucoma drugs

There are several classes of drugs currently in use for the therapeutic management of the glaucomas. Although the ocular hypotensive effects of these agents have been well characterized and described, little is known of their site of action and cellular mechanism. This review attempts to describe those cellular mechanisms that may be linked to the actions of several classes of antiglaucoma drugs. Special emphasis was placed on drug actions and 1) the adenylate cyclase system; 2) receptor-coupled phosphoinositide turnover; 3) prostaglandins and 4) ion transport processes. Models are presented depicting proposed cellular sites of the interaction of the antiglaucoma drugs with these cellular processes.

Physiology and pharmacology of aqueous humor inflow

Recent physiological and pharmacological data pertinent to aqueous humor inflow regulation have been reviewed. New anatomical and electrophysiological data are presented, particularly related to aqueous humor secretion. The action of adrenergic agonists and antagonists is discussed in relation to changes in intraocular pressure, and the effects of a variety of experimental perturbations is presented. The multiple factors which affect aqueous humor inflow are discussed in the context of an evaluation of recent pertinent literature.

Marihuana-derived material: distribution and effects after systemic administration

Studies have been made in an attempt to elucidate the mode of action of water-soluble marihuana-derived material (MDM). MDM lowers intraocular pressure (IOP) at systemic dose levels greater than 5 micrograms/rabbit by reducing aqueous humor inflow. Blood pressure, body temperature, and PO2 remain constant despite the wide variation in IOP caused by high dose levels of MDM, viz. an initial hypertensive phase followed by a hypotensive phase. Blood PCO2 and pH, however, both decrease with 1 mg MDM/rabbit indicating an acidosis which may partially explain some of the fall in IOP caused by MDM at this high dose level. Low doses of MDM (50 micrograms/animal), however, induce no such changes in systemic chemistry, illustrating the absence of an MDM effect which can explain the greater than 50% fall in IOP. Repeated injections of MDM on a weekly basis indicate a sequentially reduced effect on IOP. MDM, when incubated in vitro for 6 hours with saline, aqueous or vitreous, always induced a fall in IOP; incubation in these media for 24 hours, however, reduced the capacity to induce an IOP decrease. When aqueous or vitreous was removed from animals which had received intravitreal injections of MDM 24 hours previously (thus, at a time when the IOP in these animals was low) and was reinjected intravitreally into fresh recipient rabbits, the IOP fell in the recipients with aqueous, but not vitreous. Only when high doses of MDM (greater than or equal to 2 mg) were given systemically to a donor rabbit was any evidence obtained of a fall in IOP in recipient rabbits at short times after the donor injection (less than 10 min); at greater times after the donor injections whole blood or serum from donor rabbits failed to elicit a fall in IOP in recipient animals. These data indicate that, in vivo, MDM is bound or metabolized rapidly in rabbits when MDM is given systemically.

Water soluble marihuana-derived material: pharmacological actions in rabbit and primate

Further studies have been made with water soluble marihuana-derived material (MDM). Neither adrenergic, cholinergic, aldosterone, dopamine or serotonin antagonism affected the fall in intraocular pressure induced by MDM. Partial blockade was obtained with galactose, glucose, or mannose, but not arabinose, when the latter were given at intravenous concentrations of 1 gm/animal and MDM was given at 25 micrograms animal, suggesting that these sugars may be involved at the active site of the MDM glycoproteins. Dexamethasone was without effect on either intravenous or intravitreal MDM indicating that the MDM effect is not a non-specific response to a protein. A similar plant glycoprotein, larch arabinogalactan, at 200 micrograms/animal was without effect on intraocular pressure. Aqueous humor flow rate was increased 3 hours after MDM administration, a period corresponding to the intraocular pressure increase caused by MDM, and fell to 20% of control values when the fall in intraocular pressure occurred. Blood flow through the iris was increased at both one and six hours after intravenous MDM injection indicating a vasodilation which could contribute to the initial increase in intraocular pressure. Intravitreal injection of MDM in rabbit and rhesus monkey caused a fall in intraocular pressure only after a 24 hour delay: the unilateral response indicated that systemic metabolism was not required for activity and the delay was likely caused by the diffusion time to the ciliary processes from the mid-vitreal injection site. The changes in beta-receptors, adenylate cyclase and carbonic anhydrase in the ciliary processes are minimal indicating a possible vascular mechanism of action of MDM.