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Recent studies have suggested that the development of addictive behaviours shares common features with traditional learning models. Synaptic plasticity, a possible substrate for learning, has been demonstrated in neural reward circuits and might contribute to the learning of addictive behaviours. Changes in the strength of synaptic connections have been investigated in dopaminergic cells of the ventral tegmental area in response to several addictive drugs. Rapid and persistent forms of synaptic plasticity (specifically, long-lasting synaptic potentiation) have been demonstrated to accompany some of the behavioural effects of addictive drugs. We hypothesize that drug-induced synaptic plasticity might play a role in reward-related learning and addiction by modifying the fine tuning of dopaminergic cell firing. [Copyright &y& Elsevier]

Signalling at CB1 cannabinoid receptors plays a key role in the control of movement in health and disease. In recent years, an increased understanding of the physiological role of transmission at CB1 receptors throughout the basal ganglia circuitry has led to the identification of novel therapeutic approaches to both the symptoms of Parkinson’s disease and the side effects of current anti-parkinsonian therapies, especially L3,4 dihydroxyphenylalamine (levodopa)-induced dyskinesia. Thus, because activation of basal ganglia CB1 receptors can modulate neurotransmission and contribute to synaptic plasticity in a manner similar to that described in other brain regions, it also appears that endocannabinoids might modulate cell–cell signalling via effects on neurotransmitter re-uptake and postsynaptic actions mediating cross talk between multiple receptor types. Recent studies in animal models and in the clinic suggest that CB1 receptor antagonists could prove useful in the treatment of parkinsonian symptoms and levodopa-induced dyskinesia, whereas CB1 receptor agonists could have value in reducing levodopa-induced dyskinesia. [Copyright &y& Elsevier]

The recent appreciation that two G-protein-coupled receptors, metabotropic glutamate and cannabinoid, are trans-synaptically linked by a small lipid messenger has profound implications, both for control of synaptic transmission and for novel therapeutic strategies. There is much evidence for this assertion and on the significance of this dual receptor cooperation for modulation of synaptic transmission in the central nervous system. [Copyright &y& Elsevier]

Recent advances have been made in understanding the changes in neuronal plasticity in psychiatric disease at the molecular level (changes in neurotransmission, long-term potentiation, long-term depression, glutamate receptors, synaptic strength and neurotrophic support) and the systems level (changes in hippocampal, frontal and amygdala function in health and disease and the impact of stress on the hippocampal/frontal axis), as well as in the impact of drugs and sites of action for therapeutic intervention. Drugs acting on plasticity could affect the abnormal set point in psychiatric disease, resulting in treatment of the disease rather than just the symptoms. [Copyright &y& Elsevier]