Cannabinoid Release Research Articles

Efficient controlled release of cannabinoids loaded in γ-CD-MOFs and DPPC liposomes as novel delivery systems in oral health

Olivetol (OLV), as a cannabidiol (CBD) analog, was incorporated in γ-cyclodextrin metal-organic frameworks (γ-CD-MOFs) and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) liposomes as potential analgesic drug delivery systems (DDS) for dental hypersensitivity (DH) treatment. These DDS have been scarcely employed in oral health, being the first time in case of MOFs loaded with cannabinoids. In vitro experiments using bovine teeth were performed to verify if the drug is able to reach the dentin, where it can flow to the pulp tissues and exert its analgesic effect; enamel and dentin regions were analyzed by synchrotron radiation-based FTIR microspectroscopy. Principal component analysis (PCA) was used to process the spectroscopic data as a powerful chemometric tool, and it revealed a similar behavior in both regions. The studied DDS have been characterized by different techniques, and is was demonstrated that DDS is an efficient way to carry the drug through dental tissues without compromising their structure.Graphical

Chitosan-Coated Alginate Microcapsules of a Full-Spectrum Cannabis Extract: Characterization, Long-Term Stability and In Vitro Bioaccessibility.

Cannabinoids present in Cannabis sativa are increasingly used in medicine due to their therapeutic potential. Moreover, the synergistic interaction between different cannabinoids and other plant constituents has led to the development of full-spectrum formulations for therapeutic treatments. In this work, the microencapsulation of a full-spectrum extract via vibration microencapsulation nozzle technique using chitosan-coated alginate is proposed to obtain an edible pharmaceutical-grade product. The suitability of microcapsules was assessed by their physicochemical characterization, long-term stability in three different storage conditions and in vitro gastrointestinal release. The synthetized microcapsules contained mainly ∆9-tetrahydrocannabinol (THC)-type and cannabinol (CBN)-type cannabinoids and had a mean size of 460 ± 260 µm and a mean sphericity of 0.5 ± 0.3. The stability assays revealed that capsules should be stored only at 4 °C in darkness to maintain their cannabinoid profile. In addition, based on the in vitro experiments, a fast intestinal release of cannabinoids ensures a medium-high bioaccessibility (57-77%) of therapeutically relevant compounds. The full characterization of microcapsules indicates that they could be used for the design of further full-spectrum cannabis oral formulations.

Depolarization-initiated endogenous cannabinoid release and underlying retrograde neurotransmission in interneurons of amygdala.

The depolarization is also important for the short-term synaptic plasticity, known as depolarization-induced suppression of excitation (DSE). The two major types of neurons and their synapses in the lateral nucleus of amygdala (LA) are prone to plasticity. However, DSE in interneurons has not been reported in amygdala in general and in LA in particular. Therefore, we conducted the patch-clamp experiments with LA interneurons. These neurons were identified by lack of adaptation in firing rate of action potentials. In this study, we show for the first time a transient suppression of neurotransmission at synapses both within the local network and between cortical inputs and interneurons of the LA. The retrograde neurotransmission from GABAergic interneurons were comparable with that of glutamatergic pyramidal cells. That is the axonal terminals of cortical inputs do not posses selectivity toward two neuronal subtypes. However, the DSE of both types of neurons involve an increase in intracellular Ca2+ and the release of endogenous cannabinoids (eCB) and activation of presynaptic CB1 receptors. The magnitude of DSE was significantly higher in interneurons compared with pyramidal cells, though developed with some latency.

Cellular and behavioral basis of cannabinioid and opioid interactions: Implications for opioid dependence and withdrawal.

The brain's endogenous opioid and endocannabinoid systems are neuromodulatory of synaptic transmission, and play key roles in pain, memory, reward, and addiction. Recent clinical and pre-clinical evidence suggests that opioid use may be reduced with cannabinoid intake. This suggests the presence of a functional interaction between these two systems. Emerging research indicates that cannabinoids and opioids can functionally interact at different levels. At the cellular level, opioid and cannabinoids can have direct receptor associations, alterations in endogenous opioid peptide or cannabinoid release, or post-receptor activation interactions via shared signal transduction pathways. At the systems level, the nature of cannabinoid and opioid interaction might differ in brain circuits underlying different behavioral phenomenon, including reward-seeking or antinociception. Given the rising use of opioid and cannabinoid drugs, a better understanding of how these endogenous signaling systems interact in the brain is of significant interest. This review focuses on the potential relationship of these neural systems in addiction-related processes.

Development of a Vaping Machine for the Sampling of THC and CBD Aerosols Generated by Two Portable Dry Herb Cannabis Vaporisers

Cannabis sativa is known for its recreational use, but also for its therapeutic potential. There has been wide discussion over the use of cannabis for medical purposes in recent years, especially because a consensus has not been reached regarding its risk/benefit balance. Among the more common modes of administration, vaping with a vaporiser is most frequently used for self-medication. Vaping seems to be a better alternative to preventing adverse health effects due to toxic compounds produced during combustion when cannabis is smoked. However, the delivery kinetics and efficiency of most portable vaporisers are not fully characterised with an appropriate vaping regime. This determination requires a specific vaping machine operating under realistic puffing conditions. In this study, a vaping machine was conceived to fit with the common uses of portable vaporisers that requires conditions different from those used for electronic cigarettes. The experimental setup in this study was optimised to sample aerosolised cannabinoids. The delivery kinetics, efficiency, and decarboxylation yields of two commercially available vaporisers (DaVinci® and Mighty Medic®) were evaluated for delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD). Among all tested sampling supports, the glass fibre filter is the most efficient medium to collect mixed THC and CBD aerosols. From the delivery kinetics of cannabinoids, a single-parameter model was used to calculate the extraction coefficient of each vaporiser. The results show that the Mighty Medic® vaporiser had a higher extraction coefficient (0.39) and a more immediate release of cannabinoids than the DaVinci® vaporiser (0.16), which had a gradual and slower rate of vaporisation. This parameter could be a quantitative input in pharmacokinetic models of administration of volatile compounds using vaporisers and a useful tool for the comparison of vaporisers.

Endogenous cannabinoid release within prefrontal-limbic pathways affects memory consolidation of emotional training.

Previous studies have provided extensive evidence that administration of cannabinoid drugs after training modulates the consolidation of memory for an aversive experience. The present experiments investigated whether the memory consolidation is regulated by endogenously released cannabinoids. The experiments first examined whether the endocannabinoids anandamide (AEA) and 2-arachidonoyl glycerol (2-AG) are released by aversive training. Inhibitory avoidance training with higher footshock intensity produced increased levels of AEA in the amygdala, hippocampus, and medial prefrontal cortex (mPFC) shortly after training in comparison with levels assessed in rats trained with lower footshock intensity or unshocked controls exposed only to the training apparatus. In contrast, 2-AG levels were not significantly elevated. The additional finding that posttraining infusions of the fatty acid amide hydrolase (FAAH) inhibitor URB597, which selectively increases AEA levels at active synapses, administered into the basolateral complex of the amygdala (BLA), hippocampus, or mPFC enhanced memory strongly suggests that the endogenously released AEA modulates memory consolidation. Moreover, in support of the view that this emotional training-associated increase in endocannabinoid neurotransmission, and its effects on memory enhancement, depends on the integrity of functional interactions between these different brain regions, we found that disruption of BLA activity blocked the training-induced increases in AEA levels as well as the memory enhancement produced by URB597 administered into the hippocampus or mPFC. Thus, the findings provide evidence that emotionally arousing training increases AEA levels within prefrontal-limbic circuits and strongly suggest that this cannabinoid activation regulates emotional arousal effects on memory consolidation.

Cannabinoid-dependent potentiation of inhibition at eye opening in mouse V1

Cannabinoid (CB) signaling is a well established regulator of synaptic transmission. Recent work demonstrated that CB release is necessary for the induction of inhibitory synaptic plasticity. In primary visual cortex (V1) CB receptors are present throughout life, though their level of expression is developmentally regulated. In the input layer of V1 (layer 4, L4) these receptors show low levels of expression and colocalize with GABAergic terminals suggesting that they may play an important role in regulating GABAergic transmission. Here we show that in the developmental window extending from eye opening to the onset of the critical period for visual cortical plasticity L4 inhibitory inputs onto pyramidal neurons are highly sensitive to activation of CB release. More specifically, application of synthetic and endogenous CB receptors agonists led to a significant increase in the amplitude and frequency of both spontaneous inhibitory post-synaptic currents and miniature inhibitory post-synaptic currents. This form of inhibitory potentiation is activity-dependent, induced by repetitive bursting of pyramidal neurons and regulated by the time of eye opening. CB-dependent regulation of inhibitory drive may be a mechanism for the regulating L4 pyramidal neurons excitability and function at a time in which V1 transitions from being activated by spontaneous activity to being driven by visual inputs.

Blood Pressure Destabilization on Nonsteroidal Antiinflammatory Agents

It has been conventional wisdom for some time now that nonsteroidal antiinflammatory drugs (NSAIDs), whether selective for inhibition of cyclooxygenase 2 (COX-2) or nonselective, increase blood pressure (BP) or interfere with BP control and that acetaminophen should not have this effect.1,–,4 Controlled clinical trials have shown that NSAIDs have heterogeneous effects on clinic and 24-hour BP in normotensive and hypertensive subjects.3 The inhibition of COX-2 by NSAIDs results in decreased actions of both vasodilatory and natriuretic prostaglandins.3 In most individuals, homeostasis of plasma volume is reestablished by small, nearly undetectable increases in BP,5 whereas in patients with impaired excretory function, more substantial volume retention occurs that may be associated with hypertension, edema, and congestive heart failure.3,5 Article see p1789 Before 2002, little was known about the effects of NSAIDs on 24-hour BP in patients with arthritis who also had hypertension and/or vascular diseases.6,–,8 Because ambulatory BP has improved reproducibility compared with clinic measurements, detection of small but clinically meaningful differences in drug treatment groups9,10 is more likely to occur. Ambulatory monitoring also allows improved evaluation of pharmacodynamic effects of any drug, including the NSAIDs.6,7 For example, in the Celecoxib Rofecoxib Efficacy and Safety in Comorbidities Evaluation Trial (CRESCENT), destabilization of systolic BP control occurred for ≈18 of the 24 hours after dosing of rofecoxib at standard osteoarthritis doses of 25 mg each morning.8 In contrast, no changes from baseline in 24-hour systolic BP were observed with celecoxib or naproxen at …

Muscarinic receptor activation modulates the excitability of hilar mossy cells through the induction of an afterdepolarization

In the present study we used electrophysiological techniques in an in vitro preparation of the rat dentate gyrus to examine the effect of muscarinic acetylcholine receptor activation on the intrinsic excitability of hilar neurons. We found that bath application of muscarine caused a direct depolarization in approximately 80% of mossy cells tested, and also produced a clear afterdepolarization (ADP) in nearly 100% of trials. The ADP observed in hilar mossy cells is produced by the opening of a Na + permeant and yet largely TTX insensitive ion channel. It requires an increase in postsynaptic calcium for activation, and is blocked by flufenamic acid, an antagonist of a previously identified calcium activated non-selective cation channel ( I CAN). Further, we demonstrate that induction of an ADP in current clamp causes release of cannabinoids, and subsequent depression of GABAergic transmission that is comparable to that produced in the same cells by a more conventional 5 s depolarization in voltage clamp. By contrast, other types of hilar neurons were less strongly depolarized by bath application of muscarinic agonists, and uniformly lacked a similar muscarinic ADP. Overall, the data presented here extend our understanding of the specific mechanisms through which muscarinic agonists are likely to modulate neuronal excitability in the hilar network, and further reveal a mechanism that could plausibly promote endocannabinoid mediated signaling in vivo.

Cannabinoid Modulation of Perivascular Sympathetic and Sensory Neurotransmission

Cannabinoids are signalling molecules which elicit their vascular effects mainly via G protein-coupled CB(1) receptors and transient receptor potential (TRP) channels (chiefly vanilloid TRPV1 receptors). Cannabinoids can act at prejunctional CB(1) receptors to inhibit perivascular sympathetic neurotransmission. The effects of cannabinoids on perivascular capsaicin-sensitive sensory nerves are more complex. Certain cannabinoids can activate sensory nerves through actions on TRPV1 receptors and other TRP channels, which leads to sensory neurotransmitter release (mainly calcitonin gene-related peptide) and vasorelaxation. However, activation of TRP/TRPV1 channels can also lead to desensitization and loss of sensory nerve activity. Concentration and time of exposure may be critical in determining which of these opposite effects of cannabinoids prevails. In addition, there is evidence for the expression of CB(1) receptors on perivascular capsaicin-sensitive sensory nerves, coupled to inhibition of neurotransmitter release. There is evidence that the archetypal cannabinoid anandamide is released as a neurotransmitter in the central nervous system, and from sensory ganglia, but a release of cannabinoids from perivascular nerves has yet to be clearly demonstrated. Hence, with regard to perivascular nerves, cannabinoids appear to act principally as prejunctional modulators of neurotransmission. The diverse prejunctional effects of cannabinoids may be novel targets for therapies designed to treat vascular disease.

The mu-opioid receptor agonist morphine, but not agonists at delta- or kappa-opioid receptors, induces peripheral antinociception mediated by cannabinoid receptors.

Although participation of opioids in antinociception induced by cannabinoids has been documented, there is little information regarding the participation of cannabinoids in the antinociceptive mechanisms of opioids. The aim of the present study was to determine whether endocannabinoids could be involved in peripheral antinociception induced by activation of mu-, delta- and kappa-opioid receptors. Nociceptive thresholds to mechanical stimulation of rat paws treated with intraplantar prostaglandin E2 (PGE2, 2 microg) to induce hyperalgesia were measured 3 h after injection using an algesimetric apparatus. Opioid agonists morphine (200 microg), (+)-4-[(alphaR)-alpha-((2S,5R)-4-Allyl-2,5-dimethyl-1-piperazinyl)-3-methoxybenzyl]-N,N-diethylbenzamide (SNC80) (80 microg), bremazocine (50 microg); cannabinoid receptor antagonists N-(piperidin-1-yl)-5-(4-iodophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide (AM251) (20-80 microg), 6-iodo-2-methyl-1-[2-(4-morpholinyl)ethyl]-1H-indol-3-yl(4-methoxyphenyl) methanone (AM630) (12.5-100 microg); and an inhibitor of methyl arachidonyl fluorophosphonate (MAFP) (1-4 microg) were also injected in the paw. The CB1-selective cannabinoid receptor antagonist AM251 completely reversed the peripheral antinociception induced by morphine in a dose-dependent manner. In contrast, the CB2-selective cannabinoid receptor antagonist AM630 elicited partial antagonism of this effect. In addition, the administration of the fatty acid amide hydrolase inhibitor, MAFP, enhanced the antinociception induced by morphine. The cannabinoid receptor antagonists AM251 and AM630 did not modify the antinociceptive effect of SNC80 or bremazocine. The antagonists alone did not cause any hyperalgesic or antinociceptive effect. Our results provide evidence for the involvement of endocannabinoids, in the peripheral antinociception induced by the mu-opioid receptor agonist morphine. The release of cannabinoids appears not to be involved in the peripheral antinociceptive effect induced by kappa- and delta-opioid receptor agonists.

Cannabinoid Sensitivity and Synaptic Properties of 2 GABAergic Networks in the Neocortex

Distinct networks of gamma-aminobutyric acidergic interneurons connected by electrical synapses can promote different patterns of activity in the neocortex. Cannabinoids affect memory and cognition by powerfully modulating a subset of inhibitory synapses; however, very little is known about the synaptic properties of the cannabinoid receptor-expressing neurons (CB(1)-positive irregular spiking [CB(1)-IS]) in the neocortex. Using paired recordings in neocortical slices, we 1st report here that synapses of CB(1)-IS cells, but not synapses of fast-spiking (FS) cells, are suppressed by release of endocannabinoids from pyramidal neurons. CB(1)-IS synapses were characterized by a very high failure rate that contrasted with the high reliability of FS synapses. Furthermore, CB(1)-IS cells received excitatory inputs less frequently compared with FS cells and made significantly less frequent inhibitory contacts onto local pyramids. These distinct synaptic properties together with their characteristic irregular firing suggest that CB(1)-IS cells play different role in neocortical function than that of FS cells. Thus, whereas the synaptic properties of FS cells can allow them to impose high-frequency rhythmic oscillatory activity, those of CB(1)-IS cells may lead to disruption of fast rhythmic oscillations. Our results suggest that activity-dependent release of cannabinoids, by blocking CB(1)-IS synapses, may alter the role of inhibition in neocortical circuits.

The diverse CB1 and CB2 receptor pharmacology of three plant cannabinoids: Δ9‐tetrahydrocannabinol, cannabidiol and Δ9‐tetrahydrocannabivarin

Cannabis sativa is the source of a unique set of compounds known collectively as plant cannabinoids or phytocannabinoids. This review focuses on the manner with which three of these compounds, (-)-trans-delta9-tetrahydrocannabinol (delta9-THC), (-)-cannabidiol (CBD) and (-)-trans-delta9-tetrahydrocannabivarin (delta9-THCV), interact with cannabinoid CB1 and CB2 receptors. Delta9-THC, the main psychotropic constituent of cannabis, is a CB1 and CB2 receptor partial agonist and in line with classical pharmacology, the responses it elicits appear to be strongly influenced both by the expression level and signalling efficiency of cannabinoid receptors and by ongoing endogenous cannabinoid release. CBD displays unexpectedly high potency as an antagonist of CB1/CB2 receptor agonists in CB1- and CB2-expressing cells or tissues, the manner with which it interacts with CB2 receptors providing a possible explanation for its ability to inhibit evoked immune cell migration. Delta9-THCV behaves as a potent CB2 receptor partial agonist in vitro. In contrast, it antagonizes cannabinoid receptor agonists in CB1-expressing tissues. This it does with relatively high potency and in a manner that is both tissue and ligand dependent. Delta9-THCV also interacts with CB1 receptors when administered in vivo, behaving either as a CB1 antagonist or, at higher doses, as a CB1 receptor agonist. Brief mention is also made in this review, first of the production by delta9-THC of pharmacodynamic tolerance, second of current knowledge about the extent to which delta9-THC, CBD and delta9-THCV interact with pharmacological targets other than CB1 or CB2 receptors, and third of actual and potential therapeutic applications for each of these cannabinoids.

Climbing Fiber-Evoked Endocannabinoid Signaling Heterosynaptically Suppresses Presynaptic Cerebellar Long-Term Potentiation

Endocannabinoid signaling has been demonstrated to mediate depolarization-induced suppression of excitation at climbing fiber (CF) and parallel fiber (PF) synapses onto cerebellar Purkinje cells. Here, we show that CF-evoked release of cannabinoids (CBs) additionally suppresses a presynaptic form of long-term potentiation (LTP) at PF synapses. PF-LTP can be induced by 8 Hz PF tetanization but is blocked when the PF tetanization is paired with 4 or 1 Hz CF coactivation. CF activity can be substituted for by bath application of the CB receptor agonist WIN55,212-2 [R(+)-[2,3-dihydro-5-methyl-3-[(morpholinyl)methyl]pyrrolo[1,2,3-de]-1,4-benzoxazinyl]-(1-naphthalenyl) methanone]. In the presence of the CB1 receptor antagonist AM251 [N-1-(2,4-dichlorophenyl)-5-(4-iodophenyl)-4-methyl-N-1-piperidinyl-1H-pyrazole-3-carboxamide], CF activity no longer suppresses PF-LTP. Presynaptic potentiation can also be obtained by the adenylyl cyclase activator forskolin. WIN55,212-2 blocked this forskolin-mediated enhancement, showing that CB1 receptor activation interferes with the adenylyl cyclase-protein kinase A cascade, which participates in LTP induction. CF activity has been described to promote the induction of postsynaptic PF-long-term depression (LTD) and to impair postsynaptic PF-LTP. Our observation that CF activity blocks the induction of presynaptic LTP suggests that the CF input controls all forms of presynaptic and postsynaptic PF plasticity and that CF activity provides a "safety lock" to prevent an enhancement of transmitter release while postsynaptic AMPA receptor function is downregulated during LTD.

The puzzle of pulsatile oxytocin secretion during lactation: some new pieces

PROVIDING SUFFICIENT MILK to nursing young is necessary for infant survival and depends on periodic bolus secretion of oxytocin (OT) from the neurohypophysis during suckling. This pulsatile release maximizes myoepithelial cell contractions in the mammary gland by avoiding OT receptor desensitization (37, 44). Underlying the periodicity is the brief (4 – 6 s), synchronous, and explosive bursting of OT neurons in the supraoptic (SON) and paraventricular nuclei (PVN), the axons of which terminate at the neurohypophyseal neurohemal contact zone. These bursts (and the resultant OT release) appear with remarkably long intervals (5–20 min) despite the continual nipple stimulation provided by pups (30, 32, 38, 39), and are seldom observed during other periods of enhanced OT release. The bursting pattern maximizes frequency-dependent facilitation of OT release at neurohypophyseal terminals, and minimizes release fatigue (3–5). Understanding this periodicity remains one of the greatest challenges for OT neurobiologists. This system undergoes astonishing physiological plastic changes during pregnancy and lactation that should provide instructive clues to the process. It is now appreciated that OT

Dendritic Calcium Spikes Are Tunable Triggers of Cannabinoid Release and Short-Term Synaptic Plasticity in Cerebellar Purkinje Neurons

Understanding the relationship between dendritic excitability and synaptic plasticity is vital for determining how dendrites regulate the input-output function of the neuron. Dendritic calcium spikes have been associated with the induction of long-term changes in synaptic efficacy. Here we use direct recordings from cerebellar Purkinje cell dendrites to show that synaptically activated local dendritic calcium spikes are potent triggers of cannabinoid release, producing a profound and short-term reduction in synaptic efficacy at parallel fiber synapses. Enhancing dendritic excitability by modulating dendritic large-conductance calcium-activated potassium (BK) channels improves the spread of dendritic calcium spikes and enhances cannabinoid release at the expense of spatial specificity. Our findings reveal that dendritic calcium spikes provide a local and tunable coincidence detection mechanism that readjusts synaptic gain when synchronous activity reaches a threshold, and they reveal a tight link between the regulation of dendritic excitability and the induction of synaptic plasticity.

Cannabinoids and Ghrelin Have Both Central and Peripheral Metabolic and Cardiac Effects via AMP-activated Protein Kinase

Endocannabinoids and ghrelin are potent appetite stimulators and are known to interact at a hypothalamic level. However, both also have important peripheral actions, including beneficial effects on the ischemic heart and increasing adipose tissue deposition, while ghrelin has direct effects on carbohydrate metabolism. The AMP-activated protein kinase (AMPK) is a heterotrimeric enzyme that functions as a fuel sensor to regulate energy balance at both cellular and whole body levels, and it may mediate the action of anti-diabetic drugs such as metformin and peroxisome proliferator-activated receptor gamma agonists. Here we show that both cannabinoids and ghrelin stimulate AMPK activity in the hypothalamus and the heart, while inhibiting AMPK in liver and adipose tissue. These novel effects of cannabinoids on AMPK provide a mechanism for a number of their known actions, such as the reduction in infarct size in the myocardium, an increase in adipose tissue, and stimulation of appetite. The beneficial effects of ghrelin on heart function, including reduction of myocyte apoptosis, and its effects on lipogenesis and carbohydrate metabolism, can also be explained by its ability to activate AMPK. Our data demonstrate that AMPK not only links the orexigenic effects of endocannabinoids and ghrelin in the hypothalamus but also their effects on the metabolism of peripheral tissues.

The cannabinoid CB1 receptor antagonist SR141716 blocks the orexigenic effects of intrahypothalamic ghrelin.

The paraventricular nucleus (PVN) of the hypothalamus plays a key role in the control of appetite and energy balance. Both ghrelin and cannabinoid receptor agonists increase food intake when administered into this nucleus: this study investigated possible interactions between the two systems in relation to eating. The orexigenic effect of ghrelin (100 pmol) when infused in to the PVN was reversed by a small, systemic dose of the CB(1) cannabinoid receptor antagonist SR141716 (1 mg kg(-1)). This is the first demonstration of a functional relationship between brain ghrelin and endocannabinoid systems, and, although it needs to be further investigated, the effect of ghrelin on food intake when injected into the PVN seems to be mediated by stimulation of cannabinoid release.

Characterization of Depolarization-Induced Suppression of Inhibition Using Paired Interneuron–Purkinje Cell Recordings

Depolarization-induced suppression of inhibition (DSI) is a retrograde form of synaptic inhibition involving the Ca2+-dependent release of cannabinoids from the postsynaptic cell. DSI exerts multiple effects on presynaptic neurons: here, we establish the breakdown of DSI in its individual components at the synapses between basket and stellate cells and Purkinje cells. In the presence of tetrodotoxin, the change in IPSC frequency entirely accounted for the decrease of transmission during DSI; in contrast, without tetrodotoxin, the reductions of frequency and average amplitude gave equal contributions. In paired recordings, transmission displayed an irreversible rundown unless interneurons were recorded from with the perforated patch method. Under these conditions, a DSI of 68.8% was measured; the failure rate and the paired pulse ratio (at 20 msec intervals) increased from 1.2 to 20.2 and 95.6 to 132.6%, respectively, and the variance to mean ratio augmented 2.17-fold. Presynaptic dialysis with Cs+ led to a major potentiation of synaptic strength and to a marked reduction of DSI with respect to control potassium conditions; DSI recovered only partially when decreasing the extracellular Ca2+ concentration to match the control IPSC amplitudes. These results, combined with those of Kreitzer et al. (2002), indicate that three distinct presynaptic processes contribute to DSI: reductions of miniature frequency (13.4% of total DSI), of presynaptic action potential frequency (23.2%), and of the probability that presynaptic depolarizations elicit transmitter release (63.4%). The latter component involves a modulation of K+ channels and trial-to-trial modifications of the presynaptic signal.

Decrease in efficacy and potency of nonsteroidal anti-inflammatory drugs by chronic delta(9)-tetrahydrocannabinol administration.

Cannabinoids have been shown to increase the release of arachadonic acid, whereas nonsteroidal anti-inflammatory drugs (NSAIDs) have been shown to decrease the analgesic effects of cannabinoids. We evaluated the antinociceptive effects of chronic administration of Delta(9)-tetrahydrocannabinol (Delta(9)-THC), anandamide (an endogenous cannabinoid), arachadonic acid, ethanolamine, and methanandamide on several NSAIDs via p.o. and/or i.p. routes of administration using the mouse p-phenylquinone (PPQ) test, a test for visceral nociception. Our studies with a cannabinoid receptor (CB1) antagonist [N-(piperidin-1-yl)-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboximide hydrochloride (SR141716A)], a CB2 antagonist [N-((1S)-endo-1,3,3-trimethyl-bicyclo-heptan-2-yl]-5-(4-chloro-3-methylphenyl)-1-(4-methylbenzyl)-pyrazole-3-carboxamide) (SR144528)], and an another CB2 agonist [1,1-dimethylbutyl-1-deoxy-Delta(9)-THC (JWH-133)] were performed to better characterize PPQ interactions with cannabinoid receptors. The acute affects of Delta(9)-THC were blocked by SR141716A (i.p.) and partially blocked by SR144528 (i.p.). When NSAIDs (p.o.) were administered, the ED(50) values were as follows: 23 mg/kg aspirin, 3 mg/kg indomethacin, 5 mg/kg celecoxib, 3 mg/kg ketorolac, 57 mg/kg acetaminophen (32.3-99.8), and 0.8 mg/kg diclofenac (0.1-4.9). In animals given chronic Delta(9)-THC, only diclofenac and acetaminophen were active. Conversely, chronic methanandamide (i.p.) did not alter the antinociceptive effects of the NSAIDs. Neither the CB1 or CB2 antagonist blocked the effects of the NSAIDs. The effects of chronic arachadonic acid, ethanolamine, and anandamide could not be evaluated. In summary, our data indicate that chronic Delta(9)-THC alters the cyclooxygenase system. Alternatively, the data suggest that this alteration is not due to chronic endogenous cannabinoid release. Based upon these data, we hypothesize that human subjects who are chronic users of Delta(9)-THC may not respond to analgesic treatment with the above NSAIDs.