Dopamine cells within the ventral tegmental area of the brain are involved in motivation and reward. Drugs of abuse target these dopamine cells altering their activity and plasticity resulting in addiction. While dopamine cell activity is primarily involved in addiction, the GABA neurons in the VTA have also been shown to have an indirect role. By decreasing the activity of the inhibitory GABA inputs onto dopamine neurons abusive drugs can indirectly increase dopamine cell activity resulting in addictive behaviors. However, although GABA neurons are important in the perception of reward, much less is known about how the excitatory inputs to these cells are regulated and possibly altered by drugs of abuse. Using transgenic mice expressing GFP attached to the GAD promoter, GABA cells were located and patched using whole cell voltage clamp and EPSCs were measured. High frequency stimulation induced LTD of the excitatory inputs to GABA neurons. The endocannabinoid analogue R- methanandamide also induced LTD at these excitatory synapses. These results suggest that endocannabinoids could potentially regulate the activity of GABA cells and as a result the activity of dopamine neurons. The endocannabinoid receptor involved is likely CB1, but not TRPV1 as only the CB1 antagonist AM-251 blocked this high frequency stimulus-induced LTD. Future research could then determine if the pathways involved in this LTD could potentially be altered by drugs of abuse contributing to addiction.



College and Department

Life Sciences; Physiology and Developmental Biology



Date Submitted


Document Type





VTA, LTD, electrophysiology, endocannabinoid