"Real time" measurement of endogenous dopamine release during short trains of pulses in slices of rat neostriatum and nucleus accumbens: role of autoinhibition.
Release of endogenous dopamine elicited in slices of rat neostriatum or nucleus accumbens by a single electric pulse or by trains of 4 or 10 pulses was examined using fast cyclic voltammetry. Single electric pulses gave rise to a marked and transient increase in the extracellular concentration of dopamine in the neostriatum (by 0.43 mumol/l) and nucleus accumbens (by 0.39 mumol/l). The overflow elicited by subsequent pulses delivered at a frequency of 0.2 Hz caused separate but much smaller peaks of dopamine concentration, whereas the overflow elicited by subsequent pulses delivered at 1 Hz caused only a shoulder in the descending limb of the peak due to pulse 1. Four pulses at 5 Hz produced a monophasic response that was higher than the single pulse-evoked peak. Nomifensine 1 mumol/l greatly increased and prolonged the evoked overflow of dopamine. In the absence of nomifensine, metoclopramide 0.3 mumol/l did not change the response to a single pulse or 4 pulses delivered at 0.2 Hz but increased the response to 4 or 10 pulses at 1 Hz and to 4 pulses at 5 Hz. In the presence of nomifensine, metoclopramide increased the response to a single pulse as well as, to a greater extent, the response to 4 pulses at 0.2 Hz and 4 pulses at 1 Hz. Sulpiride 1 mumol/l produced effects similar to those of metoclopramide in the neostriatum in the presence of nomifensine.(ABSTRACT TRUNCATED AT 250 WORDS)
Limberger
N
N
Pharmakologisches Institut, Federal Republic of Germany.
Trout
S J
SJ
Kruk
Z L
ZL
Starke
K
K
D000818:Animals; D001921:Brain / Q000187:drug effects / Q000378:metabolism*; D004298:Dopamine / Q000378:metabolism*; D004558:Electric Stimulation; D008297:Male; D008787:Metoclopramide / Q000494:pharmacology; D009627:Nomifensine / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011954:Receptors, Dopamine / Q000187:drug effects; D013469:Sulpiride / Q000494:pharmacology
D011954:Receptors, Dopamine; D009627:Nomifensine; D013469:Sulpiride; D008787:Metoclopramide; D004298:Dopamine