ALGORITMOS DE FLUJO DE CARGA

SCH

Figure 34 The application of I x 10"® M SCH 23390 reversibly suppressed the current-clamp response to dopamine, Current pulses were applied through a second microelectrode, and resting membrane potential was - 59 mV,

Current (nA)

Command Potential (mV)

Figure 36 The application of 1k 10"® II SCH 23390 reversibly suppressed the voltage-clamp response to dopamine, Data were obtained by the ‘short- pulse‘ method, and holding potential was -60 mV,

inward c u r r e n t se e n in resp o n se to n o ra d re n a lin e under v o ltag e-clam p was n o t m a te ria lly a f f e c te d (F igure 36). In t hi s exam ple, a t a command p o te n tia l o f -170 mV, th e c u rren t m agnitude was reduced from -56 nA b e fo re th e a p p lic a tion o f 1 x 10~® M SCH 23390, to -40 nA a f t e r 10 minutes In c u b a tion , b u t had in c re a se d to -50 nA a g ain a f t e r 25 minutes in c u b a tion . At p o te n tia ls p o s itiv e to th e normal r e s tin g p o te n tia l, SCH 23390 had no d e te c ta b le e f f e c t.

In c o n tr a s t to th e e f f e c t s o f SCH 23390, 1 x 10“ ® M ergotamine had no d e te c ta b le e f f e c t on th e dopamine resp o n se c u rre n t m agnitude a t any of a range o f command p o te n tia ls even a f t e r in c u b a tion tim e s o f up to 45 m inutes (Fig u re 3 7 ). At p o ten tia ls p o s itiv e to th e normal r e s tin g p o te n tia l o f th e c e l l , no su p p re ssion of resp o n se was seen a t a l l . At a command p o te n tia l o f -140 mV, th e c on tro l ex p erim en tal v alu e o f dopamine-induced c u rre n t was -43 nA. Twenty m inutes a f t e r th e a d minis tra tion o f 1 x 10~® M ergotamine, th e value was reduced to - 25 nA. However, 15 minutes l a t e r , th e value had once ag ain in c re a se d to -31 nA, s u g g e s tin g th a t any v a r ia tion was not a r e s u l t of th e e f f e c t s o f erg o tamin e, b u t r a th e r of th e normal v a ri a b i l i t y of th e resp on se c u r r e n t m agnitude, Ho su p p re ssion was seen of th e resp o n se under c u rre n t-c la m p c o n dition s , and no e f f e c t was observed on th e r e s tin g c u r r e n t- v o lta g e r e la tion s hip of th e c e l l .

Some v a r i a b i l i t y h as a ls o been seen in ex p erim en ts u sin g dopamine alo n e where s u c c e s siv e run s o f p u ls e s have produced cu rv es which a re

n ot id en tic a l, b u t which d i f f e r by a few nA between ru n s a t a p a r ti c u la r command p o te n tia l.

Current (nA)