Brain dialysis and dopamine: does the extracellular concentration of dopamine reflect synaptic release?
We considered the drug-induced circling behaviour of rats monolaterally lesioned with kainic acid (KA) as a marker of the dopamine (DA) concentration in the synaptic space. D-Amphetamine produced a dose-related increase in the DA concentration of the dialysate from an intact striatum and a proportional number of ipsilateral circlings. Pargyline or L-dihydroxyphenylalanine (L-Dopa), alone or in combination with benserazide, increased the concentration of DA to a similar or even higher level than d-amphetamine, but failed to elicit a circling response. Apomorphine given after these drugs at the peak of DA accumulation always induced circling behaviour. The results suggest that released DA may undergo different inactivation processes before reaching the dialysis probe, and that these processes may be differentially affected by drug treatments. Alternatively, it may be suggested that DA can be released into the synaptic space, in a functional manner, or into the interstitial fluid, from where it cannot reach the synaptic receptors.
Pani
L
L
B.B. Brodie Department of Neuroscience, University of Cagliari, Italy.
Gessa
G L
GL
Carboni
S
S
Portas
C M
CM
Rossetti
Z L
ZL
D000818:Animals; D001058:Apomorphine / Q000494:pharmacology; D001545:Benserazide / Q000494:pharmacology; D001923:Brain Chemistry / Q000187:drug effects*; D003342:Corpus Striatum / Q000187:drug effects / Q000502:physiology; D003913:Dextroamphetamine / Q000494:pharmacology; D003956:Dialysis; D004298:Dopamine / Q000378:metabolism*; D005110:Extracellular Space / Q000378:metabolism; D007608:Kainic Acid / Q000494:pharmacology; D007980:Levodopa / Q000494:pharmacology; D008297:Male; D010293:Pargyline / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011954:Receptors, Dopamine / Q000187:drug effects / Q000502:physiology; D013239:Stereotyped Behavior / Q000187:drug effects; D013569:Synapses / Q000187:drug effects / Q000378:metabolism*; D009435:Synaptic Transmission / Q000187:drug effects
D011954:Receptors, Dopamine; D007980:Levodopa; D001545:Benserazide; D010293:Pargyline; D001058:Apomorphine; D007608:Kainic Acid; D003913:Dextroamphetamine; D004298:Dopamine