Effects of blockade of dopamine D2 receptors on extracellular citrulline levels in the nucleus accumbens during performance of a conditioned reflex fear response.
Vital microdialysis studies on Sprague-Dawley rats using HPLC showed that performance of a conditioned reflex fear response was accompanied by an increase in the extracellular level of citrulline (a coproduct of nitric oxide synthesis) in the nucleus accumbens. Administration of the dopamine D(2) receptor antagonist raclopride (10 microM) into the nucleus accumbens decreased the magnitude of the increase in the extracellular citrulline level in this structure during performance of the conditioned reflex fear response but had no effect on its behavioral measures (the level of freezing). Doses increased investigative activity in a novel context which had been inhibited by acquisition of the conditioned reflex fear response, without affecting the investigative behavior of control animals. These data suggest that the dopaminergic input and dopamine D(2) receptors control the activity of the NO-ergic system of the nucleus accumbens during performance of the conditioned reflex fear response and may control "transfer" of fear to another behavioral situation.
Saul'skaya
N B
NB
Laboratory for the Physiology of Higher Nervous Activity, I. P. Pavlov Institute of Physiology, Russian Academy of Sciences, St. Petersburg, Russia. nbs@infran.ru
Fofonova
N V
NV
Sudorgina
P V
PV
D000818:Animals; D002956:Citrulline / Q000378:metabolism*; D003214:Conditioning, Classical / Q000187:drug effects* / Q000502:physiology; D018492:Dopamine Antagonists / Q000494:pharmacology*; D065127:Dopamine D2 Receptor Antagonists; D005106:Exploratory Behavior / Q000187:drug effects / Q000502:physiology; D005110:Extracellular Space / Q000187:drug effects / Q000502:physiology; D005239:Fear / Q000187:drug effects* / Q000502:physiology; D046352:Freezing Reaction, Cataleptic / Q000187:drug effects / Q000502:physiology; D008297:Male; D017551:Microdialysis; D009043:Motor Activity / Q000187:drug effects / Q000502:physiology; D009714:Nucleus Accumbens / Q000187:drug effects* / Q000502:physiology; D020891:Raclopride / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D017448:Receptors, Dopamine D2 / Q000378:metabolism; D013997:Time Factors
D018492:Dopamine Antagonists; D065127:Dopamine D2 Receptor Antagonists; D017448:Receptors, Dopamine D2; D002956:Citrulline; D020891:Raclopride