Cannabis is one of the most widely used illicit substances and there is growing interest in the association between cannabis use and psychosis. Delta-9-Tetrahydrocannabinol (D-9-THC) the principal active ingredient of cannabis has been shown to induce psychotomimetic and amnestic effects in healthy individuals. Whether people who frequently use cannabis are either protected from or are tolerant to these effects of D-9-THC has not been established. In a 3-day, double-blind, randomized, placebo-controlled study, the dose-related effects of 0, 2.5, and 5 mg intravenous D-9-THC were studied in 30 frequent users of cannabis and compared to 22 healthy controls. D-9-THC (1) produced transient psychotomimetic effects and perceptual alterations; (2) impaired memory and attention; (3) increased subjective effects of 'high'; (4) produced tachycardia; and (5) increased serum cortisol in both groups. However, relative to controls, frequent users showed blunted responses to the psychotomimetic, perceptual altering, cognitive impairing, anxiogenic, and cortisol increasing effects of D-9-THC but not to its euphoric effects. Frequent users also had lower prolactin levels. These data suggest that frequent users of cannabis are either inherently blunted in their response to, and/or develop tolerance to the psychotomimetic, perceptual altering, amnestic, endocrine, and other effects of cannabinoids.

Introduction-Cannabinoids produce a spectrum of effects in humans including euphoria, cognitive impairments, psychotomimetic effects, and perceptual alterations. The extent to which dopaminergic systems contribute to the effects of Δ-9-tetrahydrocannabinol (Δ-9-THC) remains unclear. This study evaluated whether pretreatment with a dopamine receptor antagonist altered the effects of Δ-9-THC in humans.

These data provide prospective, empirical evidence that the DHEA-S level is increased by acute stress in healthy humans and that the DHEA-S-cortisol ratio may index the degree to which an individual is buffered against the negative effects of stress.

Acid extrusion is essential for osteoclast (OC) activity. We examined Na + and HCO3 --independent H + extrusion in ratand mouse OCs by measuring intracellular pH (pH1) changes, with the pH1 indicator BCECF (biscarboxyethyl-5-(6) carboxyfluorescein) after H+ loading with an ammonium pulse. 90% of OCs attached to glass do not possess HCO3-and Na+-independent H +-extrusion (rate of pH1 recovery = 0.043±0.007 (SEM) pH U/min, n = 26). In contrast, in OCs attached to bone, the pH1 recovery rate is 0.228±0.011 pH. U/min, n = 25. OCs on bone also possess a NH4+-permeable pathway not seen on glass. The boneinduced H+ extrusion was inhibited by salmon calcitonin (10-8 M, for 2 h), and was not present after pretreating the bone slices with the aminobisphosphonate alendronate (ALN). At ALN levels of 0.22 nmol/mm2 bone, H+ extrusion was virtually absent 12 h after cell seeding (0.004±0.002 pH U/min) and 50% inhibition was observed at 0.022 pmol ALN/mm2 bone. The Na+-independent H+ extrusion was not inhibited by bafilomycin Al (up to i-O M), although a bafilomycin Al (10-8 M) -sensitive H+ pump was present in membrane vesicles isolated from these osteoclasts. These findings indicate that Na+-independent acid extrusion is stimulated by osteoclast attachment to bone and is virtually absent when bone is preincubated with ALN, or when osteoclasts are treated with salmon calcitonin. (J. Clin. Invest.

No abstract

No abstract

We evaluated the possible involvement of intracellular Ca2+ concentration ([Ca2+]i) changes in the action of alpha v beta 3-ligands, known to regulate osteoclast function. Rat osteoclasts or mouse osteoclast-like cells, as examined by microfluorimetry and fura 2, showed a transient [Ca2+]i increase when perfused with (all 0.1 microM) vitronectin, osteopontin, polypeptide echistatin, fibronectin, and Arg-Gly-Asp-Asp and Arg-Gly-Asp-Ser peptides (10(-4) M) but not with laminin, collagen I, collagen IV, or [Ala24]echistatin, in which Ala was substituted for Arg in the Arg-Gly-Asp complex. The threshold for echistatin was 10 pM, the 50% effective concentration was 1 nM, and the median [Ca2+]i increase was 420 nM above the resting level (217 +/- 22 nM) at saturating concentration of 0.1 microM. Echistatin did not cause Mn2+ influx, and 10 microM nifedipine, 10 nM omega-conotoxin, 5 mM Ni2+, or Cd2+ did not prevent [Ca2+]i change. However, extracellular Ca2+ was needed for the [Ca2+]i increase, probably enabling ligand-integrin interaction. Polyclonal and monoclonal (LM609) antibody as well as depletion of [Ca2+]i stores with 5 microM thapsigargin and Ca(2+)-free medium abolished the [Ca2+]i increase, after restoring extracellular Ca2+. Furthermore, the LM609 antibody induced a Ca2+ signal in the presence or absence of extracellular Ca2+, suggesting that the alpha v beta 3-ligand interaction is mediated at least partially by Ca2+ mobilized from intracellular stores.

In the presence of inhibitors for mitochondrial H+-ATPase, (Na+ + K+)- and Ca2+-ATPases, and alkaline phosphatase, sealed brush-border membrane vesicles hydrolyse externally added ATP demonstrating the existence of ATPases at the outside of the membrane ("ecto-ATPases"). These ATPases accept several nucleotides, are stimulated by Ca2+ and Mg2+, and are inhibited by N.N'-dicyclohexylcarbodiimide (DCCD), but not by N-ethylmaleimide (NEM). They occur in both brush-border and basolateral membranes. Opening of brush-border membrane vesicles with Triton X-100 exposes ATPases located at the inside (cytosolic side) of the membrane. These detergent-exposed ATPases prefer ATP, are activated by Mg2+ and Mn2+, but not by Ca2+, and are inhibited by DCCD as well as by NEM. They are present in brush-border, but not in basolateral membranes. As measured by an intravesicularly trapped pH indicator. ATP-loaded brush-border membrane vesicles extrude protons by a DCCD- and NEM-sensitive pump. ATP-driven H+ secretion is electrogenic and requires either exit of a permeant anion (Cl-) or entry of a cation, e.g., Na+ via electrogenic Na+/D-glucose and Na+/L-phenylalanine uptake. In the presence of Na+, ATP-driven H+ efflux is stimulated by blocking the Na+/H+ exchanger with amiloride. These data prove the coexistence of Na+-coupled substrate transporters, Na+/H+ exchanger, and an ATP-driven H+ pump in brush-border membrane vesicles. Similar location and inhibitor sensitivity reveal the identity of ATP-driven H+ pumps with (a part of) the DCCD- and NEM- sensitive ATPases at the cytosolic side of the brush-border membrane.