Desipramine attenuates working memory impairments induced by partial loss of catecholamines in the rat medial prefrontal cortex.
BACKGROUND
The density of tyrosine hydroxylase-immunoreactive (TH-IR) axons in the prefrontal cortex of schizophrenic subjects may be reduced by as much as 50% in the deep cortical layers (Am J Psychiatry 156:1580-1589, 1999). Previously, we demonstrated that approximately 60% loss of TH-IR axons in the rat medial prefrontal cortex (mPFC) decreases local basal and stress-evoked extracellular dopamine (DA) concentrations, suggesting that moderate loss of DA axons in the mPFC is sufficient to alter the neurochemical activity of the remaining DA neurons (Neuroscience 93:497-505, 1999).


OBJECTIVE
To further assess the functional consequences of partial mPFC DA depletion, we examined the effects of 6-hydroxydopamine lesions of the rat mPFC on behavior in a T-maze delayed-response task. We also assessed whether chronic administration of the norepinephrine (NE) uptake inhibitor, desipramine (DMI), attenuates lesion-induced deficits in T-maze performance. Previous research indicates that inhibition of NE transport in the mPFC results in a concomitant increase in extracellular DA and NE.


RESULTS
Moderate loss of mPFC DA and NE (approximately 50 and 10% loss, respectively) was sufficient to impair delayed-response behavior, in part due to an increase in perseverative responding. Chronic DMI treatment (3 mg/kg delivered via osmotic pumps) impaired performance of control rats but attenuated the deficits in delayed-response behavior in rats previously sustaining loss of mPFC DA and NE (approximately 75 and 35% loss, respectively).


CONCLUSIONS
These data suggest that moderate loss of DA and NE in the prefrontal cortex is sufficient to impair cognitive function, and these behavioral effects are attenuated by inhibition of the NE transporter.
Clinton
S M
SM
Mental Health Research Institute and Department of Psychiatry, University of Michigan, Ann Arbor, MI 48109, USA.
Sucharski
I L
IL
Finlay
J M
JM
D015102:3,4-Dihydroxyphenylacetic Acid / Q000378:metabolism; D000818:Animals; D000928:Antidepressive Agents / Q000008:administration & dosage / Q000494:pharmacology*; D002395:Catecholamines / Q000378:metabolism / Q000502:physiology*; D003891:Desipramine / Q000008:administration & dosage / Q000494:pharmacology*; D004298:Dopamine / Q000378:metabolism / Q000502:physiology; D015918:Infusion Pumps, Implantable; D008297:Male; D018782:Maze Learning / Q000187:drug effects; D008569:Memory Disorders / Q000139:chemically induced / Q000523:psychology*; D008570:Memory, Short-Term / Q000187:drug effects*; D009638:Norepinephrine / Q000378:metabolism / Q000502:physiology; D016627:Oxidopamine; D017397:Prefrontal Cortex / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D011597:Psychomotor Performance / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D013563:Sympathectomy, Chemical; D013565:Sympatholytics
D000928:Antidepressive Agents; D002395:Catecholamines; D013565:Sympatholytics; D015102:3,4-Dihydroxyphenylacetic Acid; D016627:Oxidopamine; D003891:Desipramine; D004298:Dopamine; D009638:Norepinephrine