Blockade of cannabinoid receptors by SR141716 selectively increases Fos expression in rat mesocorticolimbic areas via reduced dopamine D2 function

148

100

Anxiety and panic are the most common adverse effects of cannabis intoxication; reactions potentiated by stress. Data suggest that cannabinoid (CB 1 ) receptor modulation of amygdalar activity contributes to these phenomena. Using Fos as a marker, we tested the hypothesis that environmental stress and CB 1 cannabinoid receptor activity interact in the regulation of amygdalar activation in male mice. Both 30 min of restraint and CB 1 receptor agonist treatment (D 9 -tetrahydrocannabinol (2.5 mg/kg) or CP55940 (0.3 mg/kg); by i.p. injection) produced barely detectable increases in Fos expression within the central amygdala (CeA). However, the combination of restraint and CB 1 agonist administration produced robust Fos induction within the CeA, indicating a synergistic interaction between environmental stress and CB 1 receptor activation. An inhibitor of endocannabinoid transport, AM404 (10 mg/kg), produced an additive interaction with restraint within the CeA. In contrast, fatty acid amide hydrolase (FAAH) inhibitor-treated mice (URB597, 1 mg/kg) and FAAH À/À mice did not exhibit any differences in amygdalar activation in response to restraint compared to control mice. In the basolateral (BLA) and medial amygdala, restraint stress produced a low level of Fos induction, which was unaffected by cannabinoid treatment. Interestingly, the CB 1 receptor antagonist SR141716 dose-dependently increased Fos expression in the BLA and CeA. These data suggest the CeA is an important neural substrate subserving the interactions between cannabinoids and environmental stress, and could be relevant to understanding the context-dependent emotional and affective changes induced by marijuana intoxication and the role of endocannabinoid signaling in the modulation of amygdalar activity.

Section: Discussionmentioning

confidence: 88%

Synergistic Interactions between Cannabinoids and Environmental Stress in the Activation of the Central Amygdala

Patel

Cravatt

Hillard

2004

148

100

“…For example, concomitant activation of DA D2-like receptors by endogenous DA has been found to play a role in the THCinduced memory impairment and reduction of extracellular acetylcholine concentration in the hippocampus (Nava et al, 2000), while D2, but not D1 receptor agonists, potentiate cannabinoid-induced sedation in non-human primates (Meschler et al, 2000). In addition, the alteration in Fos expression that follows the blockade of CB1 receptors has been found to occur via reduced D2-like receptor-mediated function (Alonso et al, 1999). Furthermore, D2 (but also D1) receptors participate in the THC-induced activation of the mitogen-activated protein kinase/extracellular signalregulated kinase (MAPK/ERK) in the dorsal striatum (Valjent et al, 2001).…”

Section: Da-cannabinoid Interaction and The Effects Of Cocaine In Thementioning

confidence: 99%

A Critical Interaction between Dopamine D2 Receptors and Endocannabinoids Mediates the Effects of Cocaine on Striatal GABAergic Transmission

Centonze

Battista

Rossi

et al. 2004

136

112

Compelling evidence indicates that endocannabinoids are implicated in drug addiction. In the present study, we have addressed the interaction between cocaine and endocannabinoid system by means of neurochemical and neurophysiological experiments in rat brain slices. Using gas chromatography-electron impact mass spectrometry, we have found that cocaine increased the levels of the endocannabinoid anandamide in the striatum, a brain area primarily involved in the compulsive drug-seeking and drug-taking behaviors typical of addiction. This effect was attenuated by pharmacological inhibition of D2-like receptors but not D1-like receptors, and it was mimicked by D2-like but not D1-like receptor stimulation. The cocaine-induced increase in anandamide concentrations was attributable to both stimulation of its synthesis and inhibition of its degradation, as suggested by the ability of cocaine and quinpirole, a D2-like receptor agonist, to enhance the activity of NAPE-phospholipase D and to inhibit fatty acid amide hydrolase. By means of electrophysiological recordings from single striatal neurons, we have then observed that the ability of cocaine to inhibit, via D2-like receptors, GABA transmission was partially prevented following blockade of cannabinoid receptors, suggesting that endocannabinoids may act as downstream effectors in the action of cocaine in the striatum. Understanding the molecular and physiological effects of drugs of abuse in the brain is essential for the development of effective strategies against addiction.

“…Experiments were performed as described previously (Alonso et al, 1999). Briefly, rats were anesthetized with sodium pentobarbital (75 mg/kg, i.p.)…”

Section: Fos Immunochemistrymentioning

confidence: 99%

SSR181507, A Dopamine D2 Receptor Antagonist and 5-HT1A Receptor Agonist. I: Neurochemical and Electrophysiological Profile

Claustre

Peretti

Brun

et al. 2003

monohydrochloride) is a novel tropanemethanamine benzodioxane derivative that possesses high and selective affinities for D2-like and 5-HT 1A receptors (K I ¼ 0.8, 0.2, and 0.2 nM for human D 2 , D 3 , and 5-HT 1A , respectively). In vivo, SSR181507 inhibited [ 3 H]raclopride binding to D 2 receptors in the rat (ID 50 ¼ 0.9 and 1 mg/kg, i.p. in limbic system and striatum, respectively). It displayed D 2 antagonist and 5-HT 1A agonist properties in the same concentration range in vitro (IC 50 ¼ 5.3 nM and EC 50 ¼ 2.3 nM, respectively, in the GTPgS model) and in the same dose range in vivo (ED 50 ¼ 1.6 and 0.7 mg/kg, i.p. on striatal DA and 5-HT synthesis, respectively, and 0.03-0.3 mg/kg, i.v. on dorsal raphe nucleus firing rate). It selectively enhanced Fos immunoreactivity in mesocorticolimbic areas as compared to the striatum. This regional selectivity was confirmed in electrophysiological studies where SSR181507, given acutely (0.1-3 mg/kg, i.p.) or chronically (3 mg/kg, i.p., o.d., 22 days), increased or decreased, respectively, the number of spontaneous active DA cells in the ventral tegmental area, but not in the substantia nigra. Moreover, SSR181507 increased both basal and phasic DA efflux (as assessed by microdialysis and electrochemistry) in the medial prefrontal cortex and nucleus accumbens, but not in the striatum. This study shows that the combination of D 2 receptor antagonism and 5-HT 1A agonism, in the same dose range, confers on SSR181507 a unique neurochemical and electrophysiological profile and suggests the potential of this compound for the treatment of the main dimensions of schizophrenia.