Abnormal Striatal Circuitry and Intensified Novelty Seeking among Adolescents Who Abuse Methamphetamine and Cannabis

Abstract

It has been hypothesized that changes in striatal-mediated dopamine modulation during adolescence may increase the risk for initiating substance abuse as a result of its fundamental role in arbitrating reward sensitivity and motivation during learning and decision making. However, substance abuse during adolescence may also significantly modify striatal structure and function and concomitantly alter reward sensitivity and action control while this brain region is undergoing remodeling. In the present investigation, to assess the relationship of methamphetamine (Meth) or Meth and cannabis (CA) abuse to regional striatal morphology, we acquired structural magnetic resonance images, using a 3T Siemens Trio scanner, from three groups of adolescents composed of healthy controls (n = 10), Meth abusers (n = 9) and combined Meth and CA abusers (Meth+CA, n = 8). We also assessed novelty seeking using the novelty seeking subscale of Cloninger’s Tridimensional Character Inventory. The results indicate that adolescent Meth+CA abusers have increased regional striatal volume and show intensified novelty seeking in contrast to the controls. The degree of Meth exposure was also positively correlated with regional striatal volume and novelty seeking in both the Meth and Meth+CA users. These preliminary findings support theories that propose a role for the striatum in adolescent substance abuse and further indicate that novelty seeking may be related to the initiation of, or sustained, drug use.

Striatal Morphology is Associated with Tobacco Cigarette Craving

“…In addition, our novel surface area and shape findings provide more nuanced insight into the relationship between striatal morphology and craving. The relationship between craving and left lateralized striatal volume and surface area is consistent with previous findings linking stimulant abuse with greater left striatal volume (Das et al, 2011;Churchwell et al, 2012, Ersche et al, 2012. The connection between the left striatum and substance abuse may be tied to the more dominant role of the left hemisphere in reward and approach behavior (Davidson and Irwin, 1999).…”

“…For example, enhanced striatal surface area has been associated with obsessive-compulsive disorder (OCD; Shaw et al, 2014), suggesting that larger striatal surface area may be a feature of compulsive disorders including OCD and addiction. Finally, our research focused only on the relationship between striatal morphology and cigarette craving as previous research has shown a clear link between stimulant abuse and enhanced striatal volume when substance abusers and healthy controls were compared (Das et al, 2011;Churchwell et al, 2012, Ersche et al, 2012. It is unclear whether variability in striatal morphology, in non-abusing populations also may explain individual differences in craving severity for other, more natural, reinforcers.…”

“…Recently, larger striatal volume has been linked with greater lifetime exposure to nicotine (Das et al, 2011), which calls into question whether there is a link between striatal function and structural phenotype. Although previous studies have evaluated striatal volume in the context of addiction (Churchwell et al, 2012;Das et al, 2011;Ersche et al, 2012), anomalies in subcortical shape are beginning to emerge as a robust endophenotype in neuropsychiatric disorders , suggesting that this measure may provide additional insight into the relationship between striatal morphology and substance abuse.…”

Stereological Analysis of the Brain in Methamphetamine Abusers Compared to the Controls

“…Other studies in this field also showed that the striatum volume increased following the chronic MA abuse. Even this striatum volume increment occurred in both MA active abusers and abstinence (44,45,47). Moreover, AresSantos et al, showed that MA abuse caused long-lasting loss/degeneration of dopaminergic cell bodies in the SNpc, along with destruction of dopaminergic terminals in the striatum (48).…”

“…Thanos et al showed no significant differences in the hippocampus, findings in this sense were consistent with those of the current study results. It seems that contradiction is some studies can be due to differences in timeduration and dose of MA abused by their samples (44,45). Mathias, in an experimental study on mice, reported volume reduction in hippocampus.…”