title: Age-dependent changes in cocaine sensitivity across early ontogeny in male and female rats: possible role of dorsal striatal D2(High) receptors.
abstract: BACKGROUND
  Responsiveness to acute psychostimulant administration varies across ontogeny.
  
  
  OBJECTIVE
  The purpose of the present study was to determine if age-dependent changes in D2(High) receptors may be responsible for the ontogeny of cocaine sensitivity in preweanling, adolescent, and adult rats.
  
  
  METHODS
  [(3)H]-Domperidone/dopamine competition assays were used to determine ontogenetic changes in the proportion of D2(High) receptors in male and female preweanling [postnatal day (PD) 5, 10, 15, and 20], adolescent (PD 40), and adult (PD 80) rats. In the behavioral experiment, responsiveness to cocaine (2.5, 5, 10, or 20 mg/kg) was assessed on PD 20, PD 40, and PD 80 for 60 min. Male and female rats were habituated to the apparatus on the 2 days prior to testing. Distance traveled data were presented both untransformed and as percent of saline controls.
  
  
  RESULTS
  Male and female preweanling rats (PD 5-PD 20) had a significantly greater percentage of dorsal striatal D2(High) receptors than adolescent or adult rats. Likewise, preweanling rats (PD 20) were more sensitive to the behavioral effects of cocaine than the two older age groups. Adolescent and adult rats responded in a generally similar manner; however, analysis of the untransformed locomotor activity data suggested that adolescent rats were hyporesponsive to 2.5 and 20 mg/kg cocaine when compared to adults.
  
  
  CONCLUSIONS
  Data from the present study are consistent with the hypothesis that ontogenetic changes in D2(High) receptors are responsible for age-dependent differences in psychostimulant sensitivity.
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.affiliation: Department of Psychology, California State University, 5500 University Parkway, San Bernardino, CA, 92407, USA.
authors.forename: Shannon E
authors.initials: SE
authors.lastname: Eaton
authors.affiliation: Department of Psychology, California State University, 5500 University Parkway, San Bernardino, CA, 92407, USA.
authors.forename: Alena
authors.initials: A
authors.lastname: Mohd-Yusof
authors.affiliation: Department of Psychology, California State University, 5500 University Parkway, San Bernardino, CA, 92407, USA.
authors.forename: Cynthia A
authors.initials: CA
authors.lastname: Crawford
mesh_terms: D000367:Age Factors; D000818:Animals; D000831:Animals, Newborn; D000697:Central Nervous System Stimulants / Q000494:pharmacology; D003042:Cocaine / Q000494:pharmacology*; D003342:Corpus Striatum / Q000187:drug effects* / Q000378:metabolism*; D004294:Domperidone / Q000494:pharmacology; D018492:Dopamine Antagonists / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005260:Female; D008297:Male; D009043:Motor Activity / Q000187:drug effects / Q000502:physiology; D011485:Protein Binding / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D017448:Receptors, Dopamine D2 / Q000378:metabolism*
chemical_list: D000697:Central Nervous System Stimulants; D018492:Dopamine Antagonists; D017448:Receptors, Dopamine D2; D004294:Domperidone; D003042:Cocaine
keywords: Cocaine; D2High receptors; Locomotor activity; Ontogeny