title: Behavioral effects of dopamine receptor inactivation during the adolescent period: age-dependent changes in dorsal striatal D2(High) receptors.
abstract: BACKGROUND
  Dopamine (DA) receptor inactivation produces opposing behavioral effects across ontogeny. For example, inactivating DA receptors in the dorsal striatum attenuates DA agonist-induced behaviors of adult rats, while potentiating the locomotor activity of preweanling rats.
  
  
  OBJECTIVE
  The purpose of this study was to determine if DA receptor inactivation potentiates the DA agonist-induced locomotor activity of adolescent rats and whether alterations in D2(High) receptors are responsible for this effect.
  
  
  METHODS
  In the behavioral experiment, the irreversible receptor antagonist N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ) or its vehicle (100 % dimethyl sulfoxide, DMSO) was bilaterally infused into the dorsal striatum on postnatal day (PD) 39. On PD 40, adolescent rats were given intrastriatal infusions of the DA agonist R(-)-propylnorapomorphine (NPA) or vehicle and locomotor activity was measured for 40 min. In the receptor binding experiment, rats received IP injections of EEDQ or DMSO (1:1 (v/v) in distilled water) on PD 17, PD 39, or PD 84. One day later, striatal samples were taken and subsequently assayed for D2-specific binding and D2(High) receptors using [(3)H]-domperidone.
  
  
  RESULTS
  Unlike what is observed during the preweanling period, EEDQ attenuated the NPA-induced locomotor activity of adolescent rats. EEDQ reduced D2 receptor levels in the dorsal striatum of all age groups while increasing the proportion of D2(High) receptors. Regardless of pretreatment condition (i.e., DMSO or EEDQ), preweanling rats had a greater percentage of D2(High) receptors than adolescent or adult rats.
  
  
  CONCLUSIONS
  DA receptor inactivation affects the behaviors of preweanling and older rats differently. The DA supersensitivity exhibited by EEDQ-treated preweanling rats may result from an excess of D2(High) receptors.
authors.affiliation: Department of Psychology, California State University, 5500 University Parkway, San Bernardino, CA, 92407, USA, smcdouga@csusb.edu.
authors.forename: Sanders A
authors.initials: SA
authors.lastname: McDougall
authors.forename: Joseph M
authors.initials: JM
authors.lastname: Valentine
authors.forename: Ashley E
authors.initials: AE
authors.lastname: Gonzalez
authors.forename: Danielle E
authors.initials: DE
authors.lastname: Humphrey
authors.forename: Crystal B
authors.initials: CB
authors.lastname: Widarma
authors.forename: Cynthia A
authors.initials: CA
authors.lastname: Crawford
mesh_terms: D000818:Animals; D001058:Apomorphine / Q000031:analogs & derivatives / Q000494:pharmacology; D001345:Autoradiography; D003342:Corpus Striatum / Q000187:drug effects* / Q000254:growth & development* / Q000502:physiology; D004294:Domperidone / Q000494:pharmacology; D018491:Dopamine Agonists / Q000494:pharmacology; D018492:Dopamine Antagonists / Q000494:pharmacology; D005260:Female; D008297:Male; D009043:Motor Activity / Q000187:drug effects* / Q000502:physiology*; D011804:Quinolines / Q000494:pharmacology; D051381:Rats; D017448:Receptors, Dopamine D2 / Q000819:agonists / Q000378:metabolism*; D012727:Sex Characteristics; D014316:Tritium
chemical_list: D018491:Dopamine Agonists; D018492:Dopamine Antagonists; D011804:Quinolines; D017448:Receptors, Dopamine D2; D014316:Tritium; D004294:Domperidone; C009074:N-n-propylnorapomorphine; C000470:EEDQ; D001058:Apomorphine