Cannabinoid type-1 receptor ligands, alone or in combination with cocaine, affect vigilance-related behaviors of marmoset monkeys.

Endocannabinoids (eCB) have been functionally linked to cocaine׳s rewarding effects. However, results differ at the behavioral level, with few reports in nonhuman primates (NHPs). Here we analyzed whether repeatedly administered cannabinoid type-1 receptor (CB1r) agonist WIN 55-212,2 (WIN) or antagonist AM 251 (AM) induce effects per se and if concurrent pre-treatments affect cocaine-induced changes in marmoset behavior.

Cannabinoid type 1 receptor ligands WIN 55,212-2 and AM 251 alter anxiety-like behaviors of marmoset monkeys in an open-field test.

Cannabinoid type 1 receptors (CB1r) are an important modulatory site for emotional behavior. However, little is known on the effects of CB1r ligands on emotionality aspects of primates, even with their highly similar behavioral response and receptor density/distribution as humans. Thus, we analyzed the effects of the CB1r agonist WIN 55,212-2 (WIN; 1mg/kg) and the antagonist AM 251 (AM; 2mg/kg), systemically administered prior to a single brief (15 min) exposure to a novel open-field (OF) environment, on the behavior of individually tested adult black tufted-ear marmosets.

Repeated cocaine administration in marmoset monkeys induces hypervigilance-related behaviors, but no changes in locomotion and cortisol levels.

Although cocaine induces several behavioral and hormonal effects, little is known about non-contingent repeated administrations in non-human primates. Therefore, we analyzed behavioral (locomotion, vigilance) and hormonal (cortisol) responses of adult black tufted-ear marmosets during repeated administrations and withdrawal trials. The subjects were divided into two groups (saline or cocaine 5mg/kg, ip) and submitted to nine treatment trials and four withdrawal trials in the absence of any treatment in an open-field arena.

Diazepam-induced decrease in anxiety-like behaviors of marmoset monkeys exposed to a novel open-field.

Unfamiliar environments can be a source of stress, fear and anxiety for marmoset monkeys. In spite of existing data, the influence of putative anxiolytics on the effects of novel environments has yet to be tested in primates. Therefore, the behavior of adult black tufted-ear marmosets to a single brief (15 min) exposure to a novel environment was analyzed in the presence and absence of diazepam (DZP).

Immediate, but no delayed, behavioral response to a snake model by captive black tufted-ear marmosets.

Whether callitrichids are naturally capable of detecting and responding to predators - or if such skills are learned - remains a controversial issue, with results differing in terms of species, predator and encounter conditions. Therefore, the behavioral response of naïve adult captive black tufted-ear marmosets (Callithrix penicillata) was assessed before, during, 0 and 4 h after a 5-min encounter with a snake and flower model. Using a two-phase cross-over design, marmosets (n = 16) were submitted to one trial for each stimulus, divided into four 5-min intervals: pre-exposure, exposure and post-exposure observations held 0 and 4h later.

Humans and natural predators induce different fear/anxiety reactions and response pattern to diazepam in marmoset monkeys.

The behavioral response of marmoset monkeys in the Human Threat (HT) test of anxiety, and the effects of diazepam (DZP), were compared to those in the Predator Confrontation (PC) procedure. Subjects (n=13) were initially submitted to four habituation trials, followed by four random confrontation sessions for each test (DZP 0, 1, 2 and 3 mg/kg). Each trial was divided into three consecutive 5-min intervals: pre-exposure, exposure (human observer, taxidermized oncilla cat) and post-exposure.