title: Brain stimulation reward performance and sucrose maintained behaviors in alcohol-preferring and -nonpreferring rats.
abstract: BACKGROUND
  The relation between ethanol (EtOH) preference and sensitivity to brain stimulation reward (BSR) was examined under multiples schedules of reinforcement in the current study. For comparison, the study also examined the relation between EtOH preference and motivation for a sweet, palatable sucrose solution under similar schedules of reinforcement.
  
  
  METHODS
  To investigate sensitivity to BSR performance, alcohol-preferring and -nonpreferring rats were tested using the curve-shift (rate-frequency) paradigm under several intensity levels during a 20-min session. Animals were first trained under an optimal current intensity, which produced maximal responding (i.e., 100%) across a series of descending frequencies (i.e., 300-20 Hz). BSR was then evaluated at 100%, 75%, and 50% of the optimal current. The sensitivity of the curve-shift method was further evaluated under the animal's optimal current using the FR1, FR6, and FR12 schedules. To examine responding for the sucrose solution, a separate group of alcohol-preferring and -nonpreferring rats was initially stabilized on an FR1 schedule and then subsequently on FR6 and FR12 schedules.
  
  
  RESULTS
  The results demonstrated that reducing the reinforcing efficacy of BSR via reduction in current intensity/reinforcement schedule produced marked orderly rightward shifts in the rate-frequency curves relating responding to stimulation frequency in both rat lines. However, no differences were found between the lines with either manipulation. Specifically, both lines demonstrated orderly reductions in response rate and increases in BSR threshold parameters (i.e., half maximal frequency/responding, minimum and maximum frequencies). In contrast to BSR, genetic selection for EtOH preference was highly associated with responding for the sweet, palatable sucrose solution. The association was even more salient as the reinforcement schedule increased (i.e., reward cost).
  
  
  CONCLUSIONS
  The results demonstrate that responding for BSR is not associated with EtOH preference, insofar as alcohol-preferring and -nonpreferring rats respond similarly under an array of reinforcement schedules and current intensities. In contrast, genetic selection for EtOH preference is highly associated with responding for a palatable sucrose reward, and the relation increases as the reward cost for the sucrose increases. These findings suggest that similar/overlapping mechanisms of action regulate the reinforcing properties of EtOH and sucrose but that overlapping yet distinct neuronal mechanism may modulate the reward characteristics of BSR and EtOH preference.
authors.affiliation: Psychobiology of Addictions Program, Department of Psychology, Indiana University-Purdue University, Indianapolis, Indiana 46202-3275, USA.
authors.forename: William J A
authors.initials: WJ
authors.lastname: Eiler
authors.forename: James E
authors.initials: JE
authors.lastname: Woods
authors.forename: Jacob
authors.initials: J
authors.lastname: Masters
authors.forename: Pete F
authors.initials: PF
authors.lastname: McKay
authors.forename: Lathen
authors.initials: L
authors.lastname: Hardy
authors.forename: Josh J
authors.initials: JJ
authors.lastname: Goergen
authors.forename: Boikai
authors.initials: B
authors.lastname: Mensah-Zoe
authors.forename: Jason B
authors.initials: JB
authors.lastname: Cook
authors.forename: Nathan J
authors.initials: NJ
authors.lastname: Johnson
authors.forename: Harry L
authors.initials: HL
authors.lastname: June
mesh_terms: D000428:Alcohol Drinking / Q000235:genetics / Q000523:psychology*; D000818:Animals; D001921:Brain / Q000033:anatomy & histology / Q000502:physiology*; D003216:Conditioning, Operant / Q000502:physiology*; D004558:Electric Stimulation; D005518:Food Preferences / Q000502:physiology* / Q000523:psychology*; D008297:Male; D011569:Psychiatric Status Rating Scales; D051381:Rats; D012201:Reward; D013395:Sucrose
chemical_list: D013395:Sucrose