The CB1 receptor mediates brain effects of delta 9-tetrahydrocannabinol (D-9 THC), the major psychoactive constituent of marijuana. D-9 THC and synthetic cannabinoid CB1 receptor agonists reduce in vivo acetylcholine release from hippocampus and frontal cortex (Carta et al., 1998; Gessa et al., 1998; Nava, et al., 2000; Mishima et al., 2002), and inhibit evoked [14C]-acetylcholine release in vitro from cortex and hippocampus (Gifford and Ashby, 1996; Gifford et al., 2000). Despite these findings, CB1 receptors have not to date been detected in cholinergic neurons. Therefore, we performed double in situ hybridization histochemistry on rat brain sections to identify neurons expressing CB1 mRNA or choline acetyltransferase (ChAT) mRNA (a marker for cholinergic neurons) within the striatum and septum. As reported by Hohmann and Herkenham (2000), we found that cholinergic neurons in striatum did not express detectable amounts of CB1 mRNA. These data indicate that cholinergic neurons in the striatum lack CB1 rec...

Previously, we have shown that the pre-BÖzinger complex (PBC), presumed center of respiratory rhythmogenesis, exhibited reduced cytochrome oxidase (CO; a metabolic marker) activity at postnatal days (P) 3-4 and 12, with a concomitant decrease in glutamate and NMDAR1, and an increase in GABA, GABAB, GlyR and GluR2 (J Appl Physiol 92:923-34, 2002). We hypothesized that medullary respiratory nuclei would be more affected by carotid body denervation (CBD) during these two vulnerable windows than at other times. CBD and sham surgeries were performed on rats each day from P2 to P14 and on P21. After a 3-day survival, rats were perfused and their brain stems processed for CO and neurokinins 1 receptor. Our results indicate that: 1) CO activity of PBC, ventrolateral nucleus of solitary tract (NTSVL), nucleus ambiguus (NA), and inferior olivary nucleus (ION) in CBD animals was significantly lower than that of sham controls, especially when CBD was performed at P3 and P11; 2) CO activity in the spinal trigeminal nuc...

Marijuana is the most commonly used illicit drug in the United States, but little is known about its effects on the human brain, particularly on reward/aversion regions implicated in addiction, such as the nucleus accumbens and amygdala. Animal studies show structural changes in brain regions such as the nucleus accumbens after exposure to Δ9-tetrahydrocannabinol, but less is known about cannabis use and brain morphometry in these regions in humans. We collected high-resolution MRI scans on young adult recreational marijuana users and nonusing controls and conducted three independent analyses of morphometry in these structures: (1) gray matter density using voxel-based morphometry, (2) volume (total brain and regional volumes), and (3) shape (surface morphometry). Gray matter density analyses revealed greater gray matter density in marijuana users than in control participants in the left nucleus accumbens extending to subcallosal cortex, hypothalamus, sublenticular extended amygdala, and left amygdala, eve...

Acute administration of the cannabinoid CB1 receptor agonists, delta-9-tetrahydrocannabinol (THC) or WIN 55,212-2 (WIN) affects several neurotransmitter systems, including the dopamine (DA) and acetylcholine (ACh) innervations of the prefrontal cortex (PFC). In the current studies, we examined the effects of local application of cannabinoid CB1 receptor agonist(s)/antagonist via reverse dialysis on DA and ACh release in freely moving animals using in vivo microdialysis. The infusion of THC (10 –5-10 –3 M) into the striatum produced a dose-dependent decrease in dopamine release with a maximal inhibitory effect of 50 % at a concentration of 10 –3 M but had no significant effect on acetylcholine release. Intra-striatal infusion of SR141716A (SR) (10 –5-10 –3 M), a selective CB1 receptor antagonist, was found to have no effect on transmitter release. We also tested the actions of these CB1 receptor agents infused into the PFC. THC was without effect on dopamine and acetylcholine release. However, SR was found ...

Cannabis enhances appetite. We have demonstrated a critical role for the endocannabinoid system in milk ingestion and survival of newborn mice by blocking the cannabinoid (CB1) receptor (with SR141817A). Co-administration of tetrahydrocannabinol (THC) reversed these effects. In the present experiments, we further investigated the specificity of the endocannabinoid-CB1 receptor system as a mediator of SR141716A-induced pup mortality. Mouse pups (Sabra) were injected within 24 hr after birth. (1) SR141716A-induced pup mortality was dose dependent (5-20 mg/kg). (2) The endocannabinoid 2-arachidonoyl glycerol (2-AG) did not reverse the effect of SR141716A. However, 2-AG in combination with its entourage (2-palmitoyl glycerol and 2-linoleoyl glycerol) attenuated the effect of SR141716A. (3) Cannabidiol (CBD) a non psychotropic cannabinoid which does not bind to the CB1 receptor, did not reverse the growth-arresting effects of the CB1 antagonist. (4) The CB2 (peripheral CB receptor) antagonist SR144528 did not a...

Chronic administration of cannabinoids has been shown to result in a high degree of tolerance in which physiological and behavioral functions revert back to near normal (control) levels but important second messenger pathways remain altered (Deadwyler et al., 1995; Sim et al., 1996). Large scale cDNA microarray screenings revealed an increased expression of NCAM in regions with high CB1 receptor densities-hippocampus and cerebellum, after a single high dose of Δ9-tetrahydrocannabinol (Δ9-THC, 10 mg/kg). To confirm these findings of changes in NCAM expression, in situ hybridization technique was applied for analysis of NCAM expression in different hippocampal and cerebellar subregions. In all three tested groups, vehicle-, Δ9-THC-and SR171416A+ Δ9-THC -treated animals, NCAM probe revealed distinct staining of pyramidal neurons and granule cells of the dentate gyrus. Compared to the vehicle-treated control, a significant increase in the hybridization signal of NCAM -positive cells was observed in the granula...

Krox-24 (also known as Egr-1, NGF1-A, Zif-268, and tis-8) is an immediate early gene encoding a zinc-finger transcription factor implicated in several adaptive responses, and induction by cannabinoids has been reported in vivo and in different cell lines. We used mice targeted in the Krox-24 gene to specifically dissect the role of this transcription factor in the acute and chronic central actions of cannabinoids. We report here on the ability of cannabinoids to activate G-proteins and to inhibit adenylyl cyclase activity in in vitro functional assays, and to elicit behavioral responses in wild-type and mutant mice. Analgesia and locomotor activity were assessed after a single administration of D9-tetrahydrocannabinol (D9-THC). After chronic D9-THC administration, D9-THC withdrawal was precipitated by the use of the selective antagonist of the cannabinoid receptor 1, SR141716A, and the behavioral parameters and the biochemical correlates of abstinence were evaluated. Despite minor differences in the variou...

The cannabinoid CB1 receptor (CB1R) is an abundantly expressed G-protein coupled receptor in the brain. THC (tetrahydrocannabinol), the active ingredient in marijuana, is an agonist at CB1R. In addition to THC, CP55940 is a commonly used agonist for CB1R. The agonist-receptor interactions result in activation of G proteins, particularly those of the Gi/o family, to inhibit the activity of adenylyl cyclase and regulate ion channels. In this study, CHO cell lines stably expressing CB1R (CHO-CB1R) were created. Consistent with previous observation and the expectation of Gi-coupling, CP55940 decreased the forskolin-stimulated cAMP accumulation in CHO-CB1R cells. In the presence of PTX, however, CP55940 augmented the forskolin-stimulated response, probably through Gs. The potential of CB1R activating multiple G proteins or multiple signaling pathways will be discussed.

The memory-disruptive effects of Δ9-tetrahydrocannabinol (Δ9-THC) and the synthetic cannabinoid WIN 55,212-2 (WIN-2) were assessed in rats exposed to varying doses of each drug (Δ9-THC, 0.5–2.0 mg/kg; WIN-2, 0.25–0.75 mg/kg) during performance of a delayed nonmatch to sample (DNMS) task. Cannabinoids affected performance in a dose × delay-dependent manner, with WIN-2 showing a potency more than four times that of Δ9-THC. These effects on DNMS performance were eliminated if the cannabinoid CB1 receptor antagonist SR141617A (Sanofi Research Inc.) was preadministered, but doses of the antagonist alone had no effect on performance. Simultaneous recording from ensembles of hippocampal neurons revealed that both WIN-2 and Δ9-THC produced dose-dependent reductions in the frequency (i.e.,“strength”) of ensemble firing during the sample phase of the task to the extent that performance was at risk for errors on >70% of trials as a function of delay. This decrease in ensemble firing in the Sample phase resulted from ...

Objective/Rationale: Recent reports suggest that the prevalence of cannabis use during pregnancy is upwards of 35% in North America, with a rise in use mirrored by increasing legalization and the perception of safety. This project utilizes a rat model o...