RT Journal Article
SR Electronic
T1 Regulation of somatodendritic dopamine release in the ventral tegmental area by opioids and GABA: an in vivo microdialysis study
JF The Journal of Neuroscience
JO J. Neurosci.
FD Society for Neuroscience
SP 2623
OP 2632
DO 10.1523/JNEUROSCI.12-07-02623.1992
VO 12
IS 7
A1 MA Klitenick
A1 P DeWitte
A1 PW Kalivas
YR 1992
UL http://www.jneurosci.org/content/12/7/2623.abstract
AB Microdialysis of the ventral tegmental area in conscious rats was used to evaluate the influence of opioids and GABA agonists on extracellular levels of GABA and somatodendritically released dopamine. The administration of morphine through the dialysis probe elicited significant, dose-dependent increases in the levels of extracellular dopamine and significantly reduced the extracellular concentration of GABA. In contrast, a dose-dependent decrease in somatodendritic extracellular dopamine was produced following the administration of the GABAB agonist baclofen. The increase in dopamine levels elicited by morphine (100 microM) was completely blocked by either baclofen (100 microM) coadministration or peripheral injection of naloxone (2 mg/kg, i.p.). Application of the GABAA agonist muscimol produced a significant increase in both extracellular levels of dopamine and locomotor activity. The present results, together with other electrophysiological, neurochemical, and behavioral data, support a hypothesis that stimulation of mu-opioid or GABAA receptors inhibits the activity of GABAergic afferents to dopamine neurons, thereby removing tonic inhibitory regulation, whereas stimulation of GABAB receptors directly inhibits dopamine neurons.