Distribution of CB1 Cannabinoid Receptors in the Amygdala and their Role in the Control of GABAergic Transmission

“Specifically, animal research suggests that cannabinoid signaling alters amygdala functioning by facilitating long-term depression of GABAergic interneurons within the amygdala’s basolateral nucleus [13, 14].”

“Interestingly, these effects could be blocked by prior administration of AM630 (50 nM) supporting the involvement of CB2R in the effects of JWH133 on GABAergic signaling (Morgan et al., 2009).”

“Using antibodies that preferentially recognize the dimerized form of the CB1 receptor, it has been shown that this is apparently the preferred configuration of the receptors expressed in the brain (Hajos et al., 2000; Katona et al., 2001).”

“…modulate the release of several neurotransmitters implicated in the control of emotionality, such as serotonin, dopamine (Hermann et al. 2002; Katona et al. 2001; Schlicker and Kathmann 2001; Tsou et al. 1998) and the anxiogenic neuropeptides, CCK and CRF (Ameri 1999; Rodriguez de Fonseca et…”

“…demonstrated that treatment of rats with WIN 55,212-2 and CP 55,940 suppresses the amplitude of GABAA receptormediated evoked and spontaneous inhibitory postsynaptic currents from spiny principal cells, neurons that connect fundamentally to each other with GABAergic synapses (Katona et al. 2001).”

“CB1 receptors are highly expressed on axon terminals of GABAergic interneurons in the BLA and modulate GABA release via a presynaptic mechanism (Katona et al, 2001).”

“Antibodies raised to the carboxy-terminus of CB1 have also been used to successfully detect receptors in rodent brain tissue, encompassing the entire carboxy-terminal region (Hajos et al., 2000; Katona et al., 2001; Bodor et al., 2005; Matyas et al., 2006) and also the last 13–15 amino acids (Egertova and Elphick, 200…”

“These findings extend our knowledge of endocannabinoid signaling in the BLA, a brain region rich in endocannabinoids and CB 1 receptors (Katona et al., 2001; Marsicano et al., 2002).”

“This has implications for medical conditions involving hypo-responsivity to emotional and social stimuli, such as autism.”

“basolateral complex of the amygdala (Katona et al., 2001).”

“CB1 receptors are highly expressed in the BLA, and are concentrated at presynaptic GABAergic terminals that synapse onto BLA principal neurons (Katona et al., 2001).”

“…CB1R in DMV and NTS neurones in this and other studies (Van Sickle et al. 2003) may be partly due to immunolabelling of receptors that are manufactured or metabolized in DMV neurones, analogous to labelling patterns for interneurones of the hippocampus and amygdala (Katona et al. 1999, 2001).”

“…is visible in the strata molecularis > radiatum and > oriens, where the CB1 signal is predominantly originating from the interconnecting network of inhibitory interneurons innervating the dendritic arbour of pyramidal or granular cell bodies (Katona et al. 1999, 2001; Egertov a and Elphick 2000).”

“The hippocampal formation has an unusually high density of CB1 receptors [80] and these are involved in both glutamatergic and GABAergic presynaptic processes.([81]) CB1 receptors are present on certain peri-terminal axons at astonishingly high densities,([82]) enabling endogenous and exogenous cannabinoids to potentl…”

“Consistent with previous reports (12, 13, 15, 16), CB1 mRNA was expressed in various amygdala nuclei with the highest level in the BA (Fig.”

“cally on GABAergic interneurons and glutamatergic neurons [131, 132, 162, 163].”

“The cannabinoid type 1 (CB1) receptors are widely distributed in the central nervous system, located mainly in presynaptic terminals of neurons [100] and in particular, on GABAergic interneurons expressing the α2 subunit enriched GABAA receptors [101,102].”

“CB1Rs have been shown to be coupled to G-protein (usually the Gi subtype) and are often located on the presynaptic membrane of inhibitory axons (Tsou et al., 1998; Katona et al., 1999, 2001).”

“These receptors have been shown to be localized presynaptically on GABAergic interneurons and glutamatergic neurons (Hajos et al., 2000; Hajos et al., 2001; Katona et al., 2001).”

“and here we documented co-localization of CART-immunoreactive fibers and CB1 receptors in the amygdala. Bidirectional connections between the two systems can be demonstrated immunohistochemically, although the highest levels of CART and CB1 immunoreactivity are in different amygdaloid nuclei (fig. 8 ). CB1 receptor-im…”

“The zebrafish amygdala consists of three functional networks similar to the situation described for mammals: (1) the main olfactory system, (2) the accessory olfactory-like or reproductive amygdala, and (3) the central and pallial amygdala (CeA-pAmy) network (mammalian BLA) regulating autonomic functions and mediating…”

“We focused on the type 1 cannabinoid receptor (CB1) as it is clearly expressed only on a subset of interneurons in the lateral ⁄ basolateral amygdala (Marsicano & Lutz, 1999; Katona et al., 2001).”

“BLA neurons contain CB1 receptors both at glutamatergic neurons and GABAergic interneurons (Marsicano and Lutz, 1999; Katona et al., 2001, 2006; Bellocchio et al., 2010).”

“Unlike most neurotransmitters, AEA and 2-AG are not stored in releasable pools; instead, they are rapidly synthesized “on-demand” and subserve retrograde regulation of synaptic activity through engaging presynaptic CB1R (Katona et al., 2001, Gulyas et al., 2004), and inhibiting neurotransmitter release (Bisogno et al.…”

“Experiments were carried out in accordance with the European Communities Council Directive of 24 November 1986 (86 ⁄ 609 ⁄ EEC) and were reviewed and approved by the Animal Welfare Committee of the Institute of Experimental Medicine.”

“…and undergo nearly identical changes in laminar distribution during postnatal development (Oeth and Lewis, 1993; Eggan et al , 2010); and 3) the antibody utilized in this study exclusively labels symmetric, inhibitory synapses (Katona et al , 1999; Katona et al , 2001; Eggan and Lewis, 2007).”

“CB 1 receptors are expressed in multiple brain areas, including the olfactory bulb, neocortex, pyriform cortex, hippocampus, amygdala, basal ganglia, thalamic and hypothalamic nuclei, cerebellar cortex, and brainstem nuclei (Herkenham et al., 1990, 1991; Katona et al., 2001).”

“, amygdala, hippocampus and cerebral cortex) (Fuxe and Agnati, 1985; van Eekelen et al., 1987; Ahima and Harlan, 1990; Herkenham et al., 1990; Katona et al., 2001; Korte, 2001; Bentz et al., 2010).”

“areas long associated with the regulation of emotional behaviour, including the hippocampus and amygdala (Herkenham et al., 1991; Matsuda et al., 1993; Tsou et al., 1999; Katona et al., 2001), where their activation is typically associated with presynaptically mediated inhibition of transmitter release (Schlicker and…”

“Noteworthy, CB1-r are present in the amygdala (Katona et al. 2001), where they are involved in long-term depression of”

“, including the hippocampus, amygdala, PFC and cerebellum) high in CB1 receptors [47-56] and mediating emotional [57-65] and neurocognitive processes that are altered with regular cannabinoid exposure [6, 66-77].”

“5% Triton X-100 in PB for 1 hr, which was followed by exposure to the primary antibody (Ab) rabbit anti-CB1 receptor [1:400; directed against a C-terminal sequence (Katona et al., 2001)] that was diluted in a mixture of 5% dimethylsulfoxide, 0.”

“CB1 receptors have been shown to localize presynaptically on GABAergic interneurons and glutamatergic neurons [134-136].”

“Early autoradiographic studies of the distribution of CB1R revealed the predominant expression of the receptor on axon terminals in the cerebellum (45) and this distribution pattern has been confirmed throughout the brain (79,80,119).”

“…to act as retrograde messengers at presynaptic CB1 receptors located on glutamatergic and gamma-aminobutyric acid (GABA)ergic axon terminals (Katona et al. 2001, 2006) to suppress neurotransmitter release (Wilson & Nicoll 2001), which in turn control synaptic plasticity (Katona & Freund…”

“Within the BLA, CB1 receptors are found on inhibitory local GABAergic interneurons, but are absent in the adjacent central nucleus (Herkenham et al., 1990; Tsou et al., 1998; Katona et al., 2001).”

“Moderate receptor levels are also present in the basolateral amygdala, hypothalamus, and the periaqueductal gray matter of the midbrain (Glass et al., 1997; Herkenham et al., 1991; Katona et al., 2001; Matsuda et al., 1993).”

“The bidirectional action of CB1 receptors on anxiety responses may be related to the modulatory role of these targets on GABA and glutamate release across amygdala and other forebrain areas [41,165,166].”

“amygdala (Katona et al., 2001), the hippocampus, the PFC (Mailleux”

“Cannabinoid receptors are highly expressed in many of the key regions for emotional processing (Herkenham et al., 1991; Katona et al., 2001), such as the occipital and temporal lobes, which are involved in perceptual emotional processing, the amygdala and orbital frontal cortex, which are involved…”

“In the same study, the authors failed to detect cannabinoid effects in the CeA by electrophysiological means (Katona et al, 2001), whereas another recent electrophysiological study reported that endocannabinoids regulate inhibitory transmission in the CeA (Roberto et al, 2010).”

“The BLA expresses high levels of CB1 receptors (Herkenham et al., 1991; Katona et al., 2001; McDonald and Mascagni, 2001) and CB1 mRNA (Marsicano and Lutz, 1999).”

“CCK interneurons are proposed to function as fine-tuning devices for the cooperation of pyramidal neurons, and are sensitive to the emotional and motivational state of the animal (Katona et al, 2001; Yoshida et al, 2011).”

“interneurons in the BLA but absent from the central amygdaloid nucleus (Herkenham et al., 1990; Tsou et al., 1998; Katona et al., 2001).”

“CB1 ligands have been shown to diminish inhibitory transmission in the basal and lateral nuclei of the amygdala (Marsicano et al., 2002; Azad et al., 2003) but reportedly had no effect in CeA (Katona et al., 2001), in contrast with our results.”

“In other words, even relatively large EtOH-induced changes in the expression of endocannabinoid-related genes in the CeA may be masked by the much greater presence of ECS genes in the BLA.”

“Another cell population that expresses cholecystokinin (CCK), often together with CB and type 1 cannabinoid (CB1) receptors [27] makes synapses with somata [28], suggesting analogy with cortical CCK-expressing basket cells [29].”

“Indeed, CB1 was found on GABAergic interneurons, located presynaptically on cholecystokinin (CCK)-immunoreactive basket cells (Katona et al., 1999, 2001; Tsou et al., 1999; Hájos et al., 2000).”

“The usual cellular location for the CB1R in the hippocampus and other brain regions is synaptic terminals of GABAergic interneurons and select glutamatergic principal cells [24,25,26,27,28].”

“CB1 receptors can be found on presynaptic neuron membranes of GABAergic interneurons [10,21,22] .”

“…is predominately expressed on presynaptic neurons in the brain (Huang et al., 2001; Szabo and Schlicker, 2005), particularly GABAergic interneurons (Katona et al., 2001), and the CB2 receptor is highly expressed on immune cells (Carayon et al., 1998; Galiegue et al., 1995; Schatz et al., 1997).”

“Within the BLA, CB1 receptors are highly expressed on inhibitory local c-aminobutyric acidergic (GABAergic) interneurons but are absent in the adjacent central nucleus (Herkenham et al. 1990; Tsou et al. 1998; Katona et al. 2001).”

“…of PCs in the BLA is exclusively innervated by GABAergic boutons, which were immunoreactive for type 1 cannabinoid receptors (CB1), or the Ca2+ binding proteins parvalbumin (PV), and/or calbindin (Calb) (Katona et al., 2001; McDonald and Betette, 2001; McDonald et al., 2002; Muller et al., 2006).”

“Consistent with our anatomical data, we found that activation of CB1 receptors reliably reduced eEPSC amplitude, while effects on GABAergic transmission were more variable (Katona et al., 2001).”

“Specifically, FCA is mediated by increased cannabinoid activity (Rea et al., 2013) and decreased concentration of GABA (Rea et al., 2009) within BLA, consistent with both the high concentration of CB-1 receptors (Katona et al., 2001) and the inhibition of GABAergic neurons by cannabinoids.”

“Both the amygdala [41, 42] and the hippocampal region [43] contain high levels of cannabinoid receptors making these regions likely to be affected by heavy as opposed to incidental cannabis use.”

“The findings of Katona and colleagues substantiated an important role of CB 1 activity in basolateral amygdala complex (BLA) projections that are involved in circuits regulating rewarding effects and reduction of anxiety responses (Katona et al., 2001).”

“Both GR and CB1 receptors are located within the stress circuitry in the brain (ie, amygdala, hippocampus, and PFC) (Ahima and Harlan, 1990; Herkenham et al, 1990; Katona et al, 2001; van Eekelen et al, 1987).”

“Within the amygdala, CB1 receptors are located on both glutamatergic and GABAergic terminals (Katona et al., 2001; Marsicano and Lutz, 1999; McDonald and Mascagni, 2001), yet CB1-mediated suppression of glutamate transmission dominates, resulting in an overall reduction in the firing activity of basolateral amygdala (…”

“Furthermore, there was no change in the number of CCK+ perisomatic terminals contacting fear neurons, but an upregulation of CB1Rs in CCK+ terminals contacting fear neurons that were still active after extinction.”

“areas, including the limbic system (hypothalamus, amygdala, habenula and cerebral cortex) regulating emotional and stressrelated behavior (Herkenham et al., 1990; Katona et al., 2001; Marsicano et al., 2002; Mackie, 2005).”

“Part of CR interneurons express VIP and/or CCK (Spampanato et al., 2011).”