**5. New studies on the treatment of withdrawal syndrome**

There are no drugs approved for the treatment of addiction or withdrawal syndrome of *Cannabis*. Pharmacotherapy in these cases is focused exclusively on symptoms such as increased anxiety, insomnia, loss of appetite, migraine, and irritability. We disclose these symptoms being a result of desensitization of CB1 receptors by THC studies advancing toward the development of compounds that act selectively at this receptor. There are four main chemical classes of exogenous cannabinoid ligands under study: (a) classical cannabinoids such as Δ9-THC, AM2389, cannabinol, nabilone, HU-210, and other tricyclic terpenoid derivatives, such as Δ9-tetrahydrocannabivarin (Δ9-THCV) (**Figure 6**), which contains a polar benzopyran moiety attached to a hydrophilic (*n*-pentyl) alkyl terminus [80]; (b) the nonclassical cannabinoids CP 55,940, HU-308 (**Figure 7**) and other bicyclic and tricyclic analogs of Δ9-THC without the pyran ring of classical cannabinoids [81]; (c) the aminoalkylindoles WIN55,212-2, JWH-018, JWH-073, and AM1241 (**Figure 8**), which differ in structure, lipophilicity, and binding activity at cannabinoid receptors compared to nonclassical cannabinoids [82]; and (d) biarylpyrazole ligands such as rimonabant and AM251 antagonists, which are selective for the CB1 receptor, and SR144528 (**Figure 9**), which is selective for the CB2 receptor [83].

chemical dependency, and immune function, it is important to develop in vitro bioassays activity determination and the function of these receptors [84]. The *in vitro* assays established in the studies related to CB1 and CB2 receptors involve the use of membranes or tissues containing

Bioligands Acting on the Cannabinoid Receptor CB1 for the Treatment of Withdrawal…

http://dx.doi.org/10.5772/intechopen.82184

165

**Figure 7.** Chemical structure of the non-classical cannabinoids.

**Figure 8.** Chemical structure of the aminoalkylindoles.

#### **5.1.** *In vivo* **and** *in vitro*

It is known that because cannabinoid receptors, when bound by agonists or antagonists, have the potential to treat a variety of pathologies such as pain, neurodegeneration, obesity, tumors,

**Figure 6.** Chemical structure of classical cannabinoids.

chemical dependency, and immune function, it is important to develop in vitro bioassays activity determination and the function of these receptors [84]. The *in vitro* assays established in the studies related to CB1 and CB2 receptors involve the use of membranes or tissues containing

**Figure 7.** Chemical structure of the non-classical cannabinoids.

**5. New studies on the treatment of withdrawal syndrome**

and SR144528 (**Figure 9**), which is selective for the CB2 receptor [83].

**5.1.** *In vivo* **and** *in vitro*

164 Recent Advances in Cannabinoid Research

**Figure 6.** Chemical structure of classical cannabinoids.

There are no drugs approved for the treatment of addiction or withdrawal syndrome of *Cannabis*. Pharmacotherapy in these cases is focused exclusively on symptoms such as increased anxiety, insomnia, loss of appetite, migraine, and irritability. We disclose these symptoms being a result of desensitization of CB1 receptors by THC studies advancing toward the development of compounds that act selectively at this receptor. There are four main chemical classes of exogenous cannabinoid ligands under study: (a) classical cannabinoids such as Δ9-THC, AM2389, cannabinol, nabilone, HU-210, and other tricyclic terpenoid derivatives, such as Δ9-tetrahydrocannabivarin (Δ9-THCV) (**Figure 6**), which contains a polar benzopyran moiety attached to a hydrophilic (*n*-pentyl) alkyl terminus [80]; (b) the nonclassical cannabinoids CP 55,940, HU-308 (**Figure 7**) and other bicyclic and tricyclic analogs of Δ9-THC without the pyran ring of classical cannabinoids [81]; (c) the aminoalkylindoles WIN55,212-2, JWH-018, JWH-073, and AM1241 (**Figure 8**), which differ in structure, lipophilicity, and binding activity at cannabinoid receptors compared to nonclassical cannabinoids [82]; and (d) biarylpyrazole ligands such as rimonabant and AM251 antagonists, which are selective for the CB1 receptor,

It is known that because cannabinoid receptors, when bound by agonists or antagonists, have the potential to treat a variety of pathologies such as pain, neurodegeneration, obesity, tumors,

**Figure 9.** Chemical structure of the biarylpyrazole ligands such as rimonabant and AM251 antagonists.

these receptors [85]. Of particular note is the assay using radiolabeled CB1 or CB2 receptors with [ 3 H] CP55940 (**Figure 10**) and bioassays with preparations of nerve-smooth muscle where the ability of the molecule under study to produce inhibition or excitation of cannabinoid receptors is verified [86].

*In vitro* functional bioassays measure the effects of synthetic cannabinoids and their metabolites in relation to cannabinoid receptor signaling CB1/CB2, evaluating the production of cyclic ATP and elevation of intracellular calcium. In the middle of the last century, initial studies on the effects of cannabinoids used Gayer's tests (found at the time as a useful test for the effects of THC [87]), where corneal areflexia was measured in rabbits, catatonia in mice**,** and increased defecation and aggressiveness in rats stressed by REM sleep deprivation [88]. In mice, high-dose catalepsy with Δ9-THC was also observed [95]. In rodents, the main bioassay is the measurement of locomotor activity, rectal temperature, and analgesia (in the tail or hot plate test) [89].

The sum of the various symptoms observed in the initial studies originated characteristic effects in laboratory animals called cannabinoid tetrad and being characterized by hypothermia, analgesia, catalepsy, and locomotor suppression [90]. This tetrad is widely used nowadays because, since the data obtained through its observation are qualitatively consistent, it is common to evaluate the dose-dependence relation of cannabinoids quickly and without any specific training of the animals, a fact that is configured as an advantage [89].

The Δ9-THC dependency/withdrawal modeling studies are based on the cannabinoid tetrad in which The triggered effects are verified with the administration of cannabinoid antagonist (usually rimonabant), and precipitation withdrawal symptoms, being, in general, the synthetic cannabinoids such as UR-144 (**Figure 11**), responsible to promote effects greater than that of Δ9-THC [91].

Studies in rats revealed that individual enzyme activity mainly related to the genetic polymorphisms of cytochrome P450 enzymes in the phase I metabolism of cannabinoids has an important role in determining the response of an individual on the use of cannabinoids [92]. Thus, an individual may experience attenuated effects and other individual effects exacerbated by cannabinoids, depending on the liver enzyme profile that favors the formation of antagonistic

Bioligands Acting on the Cannabinoid Receptor CB1 for the Treatment of Withdrawal…

http://dx.doi.org/10.5772/intechopen.82184

167

Technological refinement has led to the use of new techniques and different experimental models [94] in the studies of compounds in potential for reinforcement, with the search for

or agonist metabolites, respectively [93].

**Figure 11.** Chemical structure UR-144.

**Figure 10.** Chemical structure of the CP55940.

Bioligands Acting on the Cannabinoid Receptor CB1 for the Treatment of Withdrawal… http://dx.doi.org/10.5772/intechopen.82184 167

**Figure 10.** Chemical structure of the CP55940.

these receptors [85]. Of particular note is the assay using radiolabeled CB1 or CB2 receptors with

**Figure 9.** Chemical structure of the biarylpyrazole ligands such as rimonabant and AM251 antagonists.

*In vitro* functional bioassays measure the effects of synthetic cannabinoids and their metabolites in relation to cannabinoid receptor signaling CB1/CB2, evaluating the production of cyclic ATP and elevation of intracellular calcium. In the middle of the last century, initial studies on the effects of cannabinoids used Gayer's tests (found at the time as a useful test for the effects of THC [87]), where corneal areflexia was measured in rabbits, catatonia in mice**,** and increased defecation and aggressiveness in rats stressed by REM sleep deprivation [88]. In mice, high-dose catalepsy with Δ9-THC was also observed [95]. In rodents, the main bioassay is the measurement of locomotor activity, rectal temperature, and analgesia (in the tail or

The sum of the various symptoms observed in the initial studies originated characteristic effects in laboratory animals called cannabinoid tetrad and being characterized by hypothermia, analgesia, catalepsy, and locomotor suppression [90]. This tetrad is widely used nowadays because, since the data obtained through its observation are qualitatively consistent, it is common to evaluate the dose-dependence relation of cannabinoids quickly and without any

The Δ9-THC dependency/withdrawal modeling studies are based on the cannabinoid tetrad in which The triggered effects are verified with the administration of cannabinoid antagonist (usually rimonabant), and precipitation withdrawal symptoms, being, in general, the synthetic cannabinoids such as UR-144 (**Figure 11**), responsible to promote effects greater than

Studies in rats revealed that individual enzyme activity mainly related to the genetic polymorphisms of cytochrome P450 enzymes in the phase I metabolism of cannabinoids has an important role in determining the response of an individual on the use of cannabinoids [92]. Thus, an individual may experience attenuated effects and other individual effects exacerbated by

specific training of the animals, a fact that is configured as an advantage [89].

H] CP55940 (**Figure 10**) and bioassays with preparations of nerve-smooth muscle where the ability of the molecule under study to produce inhibition or excitation of cannabinoid receptors

[ 3

is verified [86].

166 Recent Advances in Cannabinoid Research

hot plate test) [89].

that of Δ9-THC [91].

**Figure 11.** Chemical structure UR-144.

cannabinoids, depending on the liver enzyme profile that favors the formation of antagonistic or agonist metabolites, respectively [93].

Technological refinement has led to the use of new techniques and different experimental models [94] in the studies of compounds in potential for reinforcement, with the search for new targets and biomarkers [95]. Among the experimental models emerges the *Danio rerio (Zebrafish*), a small fish, because it has the facility of genetic manipulation and the biology of its development [96]. *Zebrafish* is particularly useful for measuring changes in the development of the nervous system [97], and its measures of sensorimotor plasticity, emotional function, cognition, and social interaction have been used to characterize the adverse effects of drug abuse such as Δ9-THC [98, 99] due to phylogenetic analyzes, which reveal the endocannabinoid system as highly conserved between *Zebrafish* and mammals [100].

synthetic cannabinoids [104]. A study can be mentioned where computational tools were used, with the objective of proposing drug candidates for the treatment of the abstinence syndrome based on the natural ligands of this receptor. A particular compound derived from marine fungi, stemphol (**Figure 12**) [105], presented positive predictions regarding pharmacokinetic and toxicological properties for a human CB1 receptor ligand, in addition to having a relatively simple molecular structure. Due to these computational results and the recent crystallographic elucidation of the cannabinoid CB1 receptor [20], experimental studies are being conducted for the development of candidate pharmacotherapeutic alternatives for the

Bioligands Acting on the Cannabinoid Receptor CB1 for the Treatment of Withdrawal…

http://dx.doi.org/10.5772/intechopen.82184

169

Studies on cannabinoids were stimulated after the characterization and structural elucidation of Δ9-THC in the 1960s, and later on, the discovery of the cannabinoid system represented by CB1/CB2 receptors and binding substances to these receptors. Many *in vitro*, *in vivo,* and *in silico* trials have been developed in the last decades, and advances mainly regarding the mechanism of addiction, abuse, and withdrawal syndrome have been achieved. However, with the use of cannabinoid-based drugs and the chemical development of synthetic cannabinoids, further studies into these mechanisms are relevant, especially considering that Δ9-THC

It is expected in the future that the investigations will deepen the knowledge on the mechanisms of the cannabinoids, especially those that cause chemical dependence, both as cannabinoid system and as noncanabinoid physiological systems. In this way, it is possible to increase the knowledge about the different classes of these substances and, therefore, favor the development of new models and improvement of the tests currently used in the studies related to *C. sativa*.

[1] Degenhardt L, Chiu WT, Sampson N, Kessler RC, Anthony JC, Angermeyer M, et al. Toward a global view of alcohol, tobacco, cannabis, and cocaine use: Findings from the

WHO world mental health surveys. PLoS Medicine. 2008;**5**(7):1053-1067

treatment of *C. sativa* withdrawal syndrome [106].

is a low-efficacy cannabinoid compared to the "new cannabinoids."

Jaderson Vieira Ferreira, Lenir Cabral Correa, Daniel Castro da Costa

Laboratory of Pharmaceutical and Medicinal Chemistry (PharMedChem),

\*Address all correspondence to: loranehage@gmail.com

**6. Conclusion**

**Author details**

**References**

and Lorane Izabel da Silva Hage-Melim\*

Federal University of Amapá, Macapá, Brazil

Tolerance and cross-tolerance tests for cannabinoids are also performed *in vivo*, although studies indicate that not all effects of cannabinoids are developed during these tests, for example, adrenocorticotropic hormone (ACTH) secretion is not observed in rodents during these tests, indicating low reliability and the need for greater improvement *in vivo* methods used in this sense [101, 102].

#### **5.2.** *In silico*

There are several computational methods; among them, homology modeling is being used in cannabinoid studies [103], considering that the drugs utilized during the withdrawal syndrome of *C. sativa* act at a symptomatic level. The resolution of the crystalline structure of the CB1cannabinoid receptor is recent [19], and this fact favored *in silico* studies that evolve toward the planning of molecules that act as selective agonists of this receptor, mainly studies related to better understanding of the interaction and the relation structure-activity of

**Figure 12.** Chemical structure of Stemphol.

synthetic cannabinoids [104]. A study can be mentioned where computational tools were used, with the objective of proposing drug candidates for the treatment of the abstinence syndrome based on the natural ligands of this receptor. A particular compound derived from marine fungi, stemphol (**Figure 12**) [105], presented positive predictions regarding pharmacokinetic and toxicological properties for a human CB1 receptor ligand, in addition to having a relatively simple molecular structure. Due to these computational results and the recent crystallographic elucidation of the cannabinoid CB1 receptor [20], experimental studies are being conducted for the development of candidate pharmacotherapeutic alternatives for the treatment of *C. sativa* withdrawal syndrome [106].
