The Effects Of Delta-9-tetrahydrocannabinol Research Articles

Delta 9-Tetrahydrocannabinol affects mesolimbic dopaminergic activity in the female rat brain: interactions with estrogens.

In this work, we studied the possible estrogenic modulation of the effects of delta 9-tetrahydrocannabinol (THC) on mesolimbic dopaminergic activity, by examining the effects of an acute dose of this cannabinoid: (i) during the estrous cycle; (ii) after ovariectomy, chronic estrogen-replacement and tamoxifen (TMX)-induced blockade of estrogenic receptors; and (iii) combined with a single and physiological injection of estradiol to ovariectomized rats. THC significantly decreased the density of D 1 dopaminergic receptors and non-significantly increased the L-3,4-dihydroxyphenylacetic acid (DOPAC) content in the limbic forebrain of ovariectomized rats chronically replaced with estrogens. The decrease in D 1 receptors was also produced by TMX, whereas the coadministration of both THC and TMX did not lead to a major decrease. In addition to the trend of THC increasing DOPAC content, this cannabinoid was also able to increase the ratio between DOPAC and dopamine, although this last effect only occurred after coadministration of THC and TMX, which had been ineffective administered individually. All these effects were not seen when THC was administered to normal cycling rats during each phase of estrous cycle and to ovariectomized rats without chronic estrogen replacement or only submitted to a single and acute dose of estradiol. This observation might be related to the fact that the density of limbic cannabinoid receptors increased in chronic estrogen-replaced ovariectomized rats versus normal cycling, ovariectomized or acutely estrogen-treated ovariectomized rats. Interestingly, THC administration in ovariectomized rats was followed by a slight, although significant, increase in tyrosine hydroxylase activity, which was also observed after coadministration of THC with a short-time and acute dose of estradiol. In summary, THC stimulated the presynaptic activity of mesolimbic dopaminergic neurons, but accompanied by a decrease in their postsynaptic sensitivity. These effects did not appear in normal cycling rats being only evident after ovariectomy and chronic estrogen replacement, which might be related to changes in binding characteristics of cannabinoid receptors in this area. Moreover, some of them appeared after TMX-induced blockade of estrogenic cytosolic receptors, which likely suggests the existence of a certain estrogenic modulation of the actions of THC on mesolimbic neurons. On the contrary, coadministration of THC with a single and shortly tested dose of estradiol was always ineffective in modifying THC effects.

Modulation of interleukin 2 activity by delta 9-tetrahydrocannabinol after stimulation with concanavalin A, phytohemagglutinin, or anti-CD3 antibody.

The effects of delta 9-tetrahydrocannabinol (THC) on lymphocyte proliferation and interleukin (IL) 2 activity was investigated using adult murine spleen cells stimulated with either the mitogens concanavalin A, phytohemagglutinin, or anti-CD3 antibody. THC was found to suppress mitogen-induced proliferation, but to enhance anti-CD3-antibody-induced proliferation. These results reflected THC-induced suppression of Ly2 cells following concanavalin A or phytohemagglutinin stimulation and THC-induced enhancement of Ly2 cells following CD3 stimulation. The combination of THC and concanavalin A or phytohemagglutinin resulted in suppressed IL-2 activity, whereas the combination of THC and anti-CD3 antibody resulted in enhanced IL-2 activity. This drug-related modulation of IL-2 activity corresponded to the changes in blastogenic activity as well as to variations in numbers of Tac positive cells. These results suggest that the dysregulation in immune responses following THC treatment, either suppression or enhancement, may relate to the effects of THC on IL-2 production.

Marijuana and immunity: Tetrahydrocannabinol-mediated inhibition of growth and phagocytic activity of the murine macrophage cell line, P388D1

The effects of delta-9-tetrahydrocannabinol (THC) on the growth, DNA synthesis and phagocytic activity of P388D1, a murine macrophage cell line, were investigated. Incubating cell cultures with THC resulted in a dose-dependent inhibition of cell propagation and DNA synthesis. The magnitude of these effects was dependent upon the number of cells in the culture as well as the protein content in the culture medium. As the cell number increased, the THC effect decreased. Using cell cultures in which the cell concentration was standardized, THC (⩾ 5 μg/ml) produced pronounced inhibitions of cell growth and DNA synthesis, while lower THC concentrations (⩽ 3 μg/ml) were less effective. Studies examining the phagocytic activity of the P388D1 cells indicated exposure to THC (5 μg/ml for 2 h) only marginally affected the association of latex beads with the external surface of the plasma membrane. However, the ability of these THC-treated cells to internalize the latex particles was severely depressed. Thus, the data indicate that THC inhibited the growth and functional activity of murine macrophages in vitro and suggests that the P388D1 cell line is a useful model to study the effects of cannabinoids on the phagocytic process.

Delta 9-Tetrahydrocannabinol suppresses macrophage extrinsic antiherpesvirus activity.

The effect of delta 9-tetrahydrocannabinol (THC), the major psychoactive component of marijuana, on macrophage intrinsic and extrinsic antiherpesvirus activities was examined. THC had no effect on the capacity of the macrophage-like cells RAW264.7, J774A.1, and P388D1 to take up virus. In addition, replication of virus within macrophages did not occur regardless of drug treatment, indicating that THC had no effect on macrophage intrinsic antiviral activity. In contrast, the cannabinoid exerted a dose-dependent inhibition of macrophage extrinsic antiviral activity. This activity describes that macrophage function by which these cells suppress virus replication within xenogeneic cells in an interferon-independent manner. The inhibitory effect of THC on extrinsic antiviral activity was greatest on RAW264.7 and J774A.1 cells, followed by P388D1 cells. These macrophage-like cells regained their extrinsic antiviral activity in a time-related fashion following removal of the drug. These results indicate that THC inhibits macrophage extrinsic antiherpesvirus activity, but has no effect on intrinsic antiviral activity. However, the suppressive effect of THC on extrinsic antiviral activity is reversible upon removal of the drug.

Evidence for a direct anterior pituitary site of delta-9-tetrahydrocannabinol action

The effects of delta-9-tetrahydrocannabinol (THC), alone and in the presence of estradiol (E), on several estrogen-sensitive parameters in the immature female rat were examined, and it was demonstrated that THC administration antagonized the stimulatory effects of E on anterior pituitary weight and on both the secretion and pituitary content of prolactin. In the current study, the anterior pituitary gland was examined as a potential site of THC action in the ability of this cannabinoid to antagonize E-induced stimulation of pituitary function. A stimulatory dose of E (1 nM) significantly elevated prolactin levels in pituitary cells derived from either immature or retired breeder animals. Whereas THC (1 μM) alone had no effect on prolactin levels when compared to controls, THC completely prevented the E-induced increase in media prolactin levels. Moreover, THC blocked the ability of E to desensitize pituitary cells to the inhibitory influence of dopamine. Together with the findings that THC inhibited E-induced stimulation of total RNA synthesis in pituitary cell cultures, these data strongly suggest that THC antagonizes the stimulatory effect of E on the pituitary by a direct action at the adenohypophyseal level.

Tissue glutathione levels in mice treated with delta-9-tetrahydrocannabinol

Glutathione (GSH) is widely distributed among living cells and is involved in many biological functions. It provides the sulfhydryl groups for conjugation of toxic metabolites of several xenobiotica. Acetaminophen (Tylenol) toxicity is a classical example of this property. For this purpose, we studied the effects of delta-9-tetrahydrocannabinol (THC) on tissue levels of GSH in the mice. Groups of male Swiss Webster mice weighing 25±5 g were treated with 50 mg/kg, PO THC at 1300 h. Control mice were given equal volume of sesame oil (5 ml/kg, PO) which was the vehicle for THC. Ninety minutes following THC administration, mice were sacrificed, their plasma, brain, heart, liver, kidney and testis were collected. All tissues were homogenized in 5% TCA/EDTA solution and supernatant solutions of these homogenates were diluted. In these diluted samples, levels of GSH were determined by a modified spectrophotometric procedure and the GSH levels were expressed as micromoles of GSH/g tissue. In this study, THC caused no effects on GSH levels in brain, heart, testis and plasma. However, GSH levels in liver and kidney were decreased by 14% and 7% respectively. Although the decrease in kidney GSH levels were insignificant, these changes in liver and kidney could be indicative of a possible metabolic and/or dispositional interaction between THC and different commonly available drugs such as acetaminophen.

Delta-9-tetrahydrocannabinol depresses inward sodium current in mouse neuroblastoma cells

Whole-cell voltage-clamp techniques were used in order to define the effects of delta-9-tetrahydrocannabinol (THC) on the voltage-gated sodium current in neuroblastoma cells. With regard to the inward sodium current, THC decreased the peak amplitude and increased both the time to peak and tau for recovery. The reversal potential was unchanged, suggesting that channel selectivity for sodium was not altered by the drug. With regard to the outward sodium current, THC had no effect on the peak amplitude, time to peak or tau for recovery. This functional alteration of the voltage-gated sodium channel may contribute to the depressant effects of the cannabinoid.

The effect of delta-9-tetrahydrocannabinol (THC) on the production of eicosanoids and interleukin-1 by mouse peritoneal macrophages

The effect of delta-9-tetrahydrocannabinol (THC) on the production of eicosanoids and interleukin-1 by mouse peritoneal macrophages

Marijuana and immunity: Tetrahydrocannabinol mediated inhibition of lymphocyte blastogenesis

The effects of delta-9-tetrahydrocannabinol (THC) and its major metabolite, 11-OH delta-9-tetrahydrocannabinol (11-OH THC) on mitogen driven lymphocyte blastogenic transformation (LBT) were studied. THC inhibited LBT responses to the T lymphocyte mitogens phytohemagglutinin and concanavalin A but not the B lymphocyte stimulant pokeweed mitogen. The metabolite 11-OH THC caused a comparable, but less sifnificant, inhibition of LBT responses to the T cell mitogens. These inhibitions were dependent upon the drug doses and the time of incubation with the lymphocytes. There was no significant inhibitory actvity of THC to the LBT when it was added 24 or 48 h after mitogen. In addition, exposure of lymphocytes to THC for 3 h, followed by removal of the drug prior to addition of mitogen had no effect on the cells' ability to respond to the mitogen. Thus, there appears to be specified temporal period during which exposure of lymphocytes to THC results in an inhibition of blastogenesis. Interleukin 2 (30 units/ml) could not preclude the THC induced inhibition of lymphocyte blastogenesis. We conclude that THC and 11-OH THC inhibit T lymphocyte blastogenesis. However, unlike the THC mediated inhibition of natural killer cell activity (as shown previously), the process is not responsive to the cytokine intetleukin 2.

Effects of delta-9-tetrahydrocannabinol on in vitro energy substrate metabolism in mouse and rat testis

In this in vitro radiorespirometric study, the effects of delta-9-tetrahydrocannabinol (THC) on glucose and fructose metabolism in the rat and mouse testes were compared. In the rat testis, THC caused a dose-dependent decrease of 15, 18, 20 and 25% in glucose metabolism with 0.1, 0.2 and 0.3 mM concentrations. Similarly, a 39% inhibition in fructose metabolism was observed when rat testes were exposed to 0.3 mM THC. The comparative studies with mouse testis indicated that 0.1, 0.2 and 0.3 mM THC produced a 4, 12 and 30% decrease in glucose utilization where as a much greater decrease of 13, 30 and 41% in fructose utilization was observed with the same doses of THC. On the basis of these observations in these two animal models, it is concluded that THC has the ability to inhibit energy substrates utilization in the rat and mouse testis. This inhibition of cellular energetics may, in part, be responsible for most of the gonadal effects of THC.

Δ9-Tetrahydrocannabinol facilitates striatal dopaminergic transmission

We examined the effects of delta 9-tetrahydrocannabinol (THC) on striatal dopaminergic neurons in rats. THC inhibited the uptake of 3H-dopamine (DA) into striatal synaptosomes. THC facilitated the release of endogenous DA but not dihydroxyphenylacetic acid (DOPAC) from striatal slices. The concentration of DA in the dorsolateral striatum was reduced by THC. We propose that THC may stimulate nigrostriatal dopaminergic neurotransmission mainly by inhibiting uptake of DA and by facilitating release of DA.

Prevention and reversal of delta-9-tetrahydrocannabinol induced depression of natural killer cell activity by interleukin-2

The effects of delta-9-tetrahydrocannabinol (THC) on NK cell activity were studied. Previously, we reported that incubation of human peripheral blood mononuclear cells in THC resulted in an inhibition of natural killer (NK) cell activity. The present study examined the mechanism(s) of the decrease in NK cell activity. The inhibition of killing by NK cells was not due to a failure of NK cells to bind to K562 target cells. Furthermore, indomethacin did not abrogate the THC-mediated effect, suggesting that prostaglandins are not involved in the process leading to suppression of NK cell activity. However, NK activity was partially restored if cells, pretreated with THC, were washed to remove excess drug and then incubated overnight in fresh medium before assay. Addition of 1 – 100 U IL-2, either during pretreatment with THC or during overnight incubation, precluded or promoted the reversal of the inhibition of NK cell cytotoxicity. We conclude that the regulatory mechanism(s) involved in depression of NK cell cytotoxicity by THC is significantly influenced by IL-2.

Inhibition of suckling-induced milk ejections in the lactating rat by delta 9-tetrahydrocannabinol.

The effect of delta 9-tetrahydrocannabinol (THC) on suckling-induced oxytocin release was investigated by recording intramammary pressure changes in suckled rats treated iv with THC (0.5 mg/kg BW) or vehicle. Latency to the first posttreatment milk ejection and posttreatment milk ejection intervals and pressure wave amplitudes were compared between THC- and vehicle-treated rats. Before treatment, intervals between milk ejections averaged 6.5 +/- 1.3 (+/- SE) and 7.0 +/- 0.7 min for vehicle- and THC-treated groups, respectively. Vehicle injections did not alter the frequency of milk ejections, which continued at an overall mean interval of 7.6 +/- 0.7 min after treatment. In contrast, THC treatment was followed by a transient suspension of milk ejections, with a latency of 59.3 +/- 7.4 min before the first posttreatment milk ejection was recorded (P less than 0.001). Intervals between subsequent ejections averaged 15.3 +/- 2.0 to 16.1 +/- 1.3 min and were lengthened relative to corresponding intervals in vehicle-treated animals (P less than 0.05). The amplitudes of pressure waves were not significantly affected by treatment. Oxytocin (0.5 mU) injections 10 or 30 min after THC treatment evoked abrupt increases in intramammary pressure, indicating continued responsiveness of the mammary gland to oxytocin stimulation. These data suggest that THC interferes with the release of oxytocin in response to suckling. To our knowledge, this provides the first evidence that THC inhibits posterior pituitary function.

Effects of daily administration of tetrahydrocannabinol on rat preovulatory follicles. A quantitative electron-microscopic analysis.

Using morphometric techniques, we analyzed the effects of delta 9-tetrahydrocannabinol (THC) on the ultrastructure of rat preovulatory follicles. Rats were injected intraperitonally once daily with vehicle alone, or with vehicle plus THC on diestrus (D), metestrus (M) and diestrus (D), or on estrus (E), M and D. All animals were killed on proestrus. Nuclear, mitochondrial, lipid droplet and lysosomal volume density in the membrana granulosa were analyzed. There was no change in nuclear volume, but there were significant THC-induced decreases in mitochondrial and lipid droplet volumes in the peripheral region of the granulosa. There were increases in dense-body volume in all regions of the granulosa from rats given THC either on D alone, or M and D. Dense-body volume returned to control levels in rats injected on E, M and D. It appears that THC can affect follicular ultrastructure and the effects change with the number of injections.

Age-associated differences in cannabinoid-induced suppression of murine spleen, lymph node and thymus cell blastogenic responses

The effects of delta 9-tetrahydrocannabinol (THC) and 11-OH THC on the proliferative responses of murine thymus, spleen and lymph node cells were examined. Specifically, weanling and adult mouse lymphocytes were stimulated in vitro with the T-cell mitogens concanavalin A and phytohemagglutinin. Thymus cells were suppressed at lower cannabinoid concentrations than cells from either spleen or lymph nodes. However, splenic cells from weanling mice were much more readily suppressed than were those from adult animals. Lymphoid cell numbers were varied from 1 × 106 to 8 × 106 cells/ml/culture and treated with a constant dose of THC or 11-OH THC. The smallest number of cells from the spleen or lymph nodes resulted in the greatest suppression. Thymus cells, however, were more readily suppressed than spleen or lymph node cells, regardless of the number of cells in culture. Furthermore, 11-OH THC suppressed the responses of the thymus cells to phytohemagglutinin more than to concanavalin A. The proliferative responses of spleen and lymph node cells from weanling mice to concanavalin A and phytohemagglutinin were much more readily suppressed than were cells from adult mice. This age-related difference was seen in the dose-response studies as well as in the studies with varying cell numbers in culture. In all cases, spleen and lymph node cells from younger mice were more readily suppressed to concanavalin A and phytohemagglutinin than those from older mice when treated with the cannabinoid preparations.

Cannabinoids reduce fertility of sea urchin sperm.

Cannabinoids are potent pharmacological substances derived from marihuana. The effects of delta 9-tetrahydrocannabinol (THC), cannabinol (CBN), and cannabidiol (CBD) on fertilization in the sea urchin Strongylocentrotus purpuratus were investigated. Insemination of THC-treated eggs (5-400 microM) with excess sperm did not result in polyspermic fertilization. At minimal sperm densities, THC (0.1-10 microM) inhibited fertilization in a dose-dependent manner. Pretreatment of eggs with THC did not reduce their receptivity to sperm. Pretreatment of sperm with THC reduced their fertilizing capacity. The concentration of THC required to reduce sperm fertility by 50% was 1.1 +/- 1.1 microM. The fertilizing capacity of THC-treated sperm depended on concentration of sperm and duration of pretreatment. The fertility of sperm at minimal densities was reduced by 50% at 129.3 +/- 43 s treatment with 10 microM THC. The adverse effect of THC on sperm fertility was reversible. CBN and CBD at comparable concentrations (0.1-10 microM) inhibited fertilization in a manner similar to THC. First division was not delayed in zygotes that were fertilized with sperm pretreated with 10 microM THC. These studies show that cannabinoids directly affect the process of fertilization in sea urchins by reducing the fertilizing capacity of sperm.

Delta-9-tetrahydrocannabinol stimulates ABP secretion from rat sertoli cells in vitro

The effect of delta-9-tetrahydrocannabinol (THC) on rat Sertoli cell function was investigated. THC significantly increased ABP secretion by 1.5- to 2.1-fold but did not consistently enhance the stimulation of ABP induced by FSH, testosterone or dibutyryl cyclic AMP. ABP was measured by steady-state polyacrylamide gel electrophoresis, DEAE Bio-Gel and immunoassay; all three methods gave similar results. The minimal concentration of THC that stimulated ABP was 10 ng/ml; maximal stimulation was observed with 100–200 ng/ml. This effect was specific since THC did not affect gamma glutamyl transpeptidase activity or the secretion of plasminogen activator, lactate and transferrin. This observation that THC affects ABP secretion specifically is the first report of any differential effect of a drug on Sertoli cell secretion.

The effect of delta-9-tetrahydrocannabinol on rat cerebrospinal fluid.

The effect of delta-9-tetrahydrocannabinol (THC) on cerebrospinal fluid (CSF) flow in rats was studied. The ventricular system of rats anesthetized with ketamine sulfate was cannulated via cisternal puncture, and CSF production was recorded. When administered in doses of 25 mg/kg to 45 mg/kg intraperitoneally, THC caused inhibition of CSF flow; in larger doses a smaller response was noted. In response to THC, CSF flow showed an initial drop, a return toward baseline, and a secondary decrease. It is postulated that this biphasic effect is due to a combination of THC's sympathomimetic effects on the CNS plus the local action that this drug has on choroidal synaptosomal neurotransmitters.

Interactions of delta 9-tetrahydrocannabinol (THC) with hypothalamic neurotransmitters controlling luteinizing hormone and prolactin release.

The effects of delta 9-tetrahydrocannabinol (THC) on hypothalamic norepinephrine (NE) and dopamine (DA) turnover and hypothalamic serotonin (5-HT), 5-hydroxyindole acetic acid (5-HIAA) and LHRH content preceding and during a progesterone- (P) induced LH and prolactin (PRL) surge were investigated in ovariectomized estrogen-primed rats. THC had no effect on basal LH levels, but it inhibited basal PRL levels and blocked the surges of both LH and PRL. The turnover of NE, as estimated by measuring NE depletion after inhibition of tyrosine hydroxylase with alpha-methyl tyrosine (250 mg/kg), in both the anterior (AH) and medial basal hypothalamus (MBH) was significantly inhibited by THC. THC did not significantly affect AH or MBH DA or 5-HT content nor MBH-DA-turnover. Hypothalamic LHRH levels were significantly elevated 4 h after THC administration as compared to the vehicle-injected controls, but pituitary response to exogenous LHRH was not affected. These data suggest that THC inhibits the steroid-induced positive feedback release of LH by reducing NE metabolism and the release of hypothalamic LHRH. Although the mechanism for the inhibition of PRL release by THC is not clear from these experiments, it does not appear that alterations in DA turnover are a contributing factor.

Effect of delta 9-tetrahydrocannabinol on cyclic nucleotides in synchronously dividing Tetrahymena.

Cyclic nucleotide levels were determined in division-synchronized Tetrahymena and the effect of delta 9-tetrahydrocannabinol (THC) on the cyclic nucleotide levels was studied. In non-drug-treated division-synchronized cells, there was no statistically significant variation in the level of cAMP and cGMP during the G2 period, preceding the first division. During the free running cell cycle (the interval of time between the first and second synchronous division) the twofold increase in the level of cAMP was statistically significant; however the variation in the level of cGMP was not statistically significant. THC caused a lowering of cAMP and cGMP levels throughout the 4-experimental treatment. The suppression of cAMP and cGMP levels altered the cyclic nucleotide pattern of the cell cycle. The cAMP pattern was changed particularly in the G2 period preceding the first synchronous division, and immediately after division during the free running cell cycle. THC treatment caused division delays of approximately 8-15 min in the onset of the first and second synchronous division. However, the duration of the free running cell cycle (110-120 min) was unchanged. The suppression of cyclic nucleotide levels resulting from THC treatment is discussed in relation to delays in the division schedule.