Psychology. (Abstracts-2003 Annual Meetings)‪.‬

Investigation of the Effects of a Depressant and a Stimulant on Brain Stimulation Reinforcement. Rebecca Foster, Sacha Shellenbarger, John Renfrew, and Cynthia Prosen, Northern Michigan University, Psychology Department, Marquette, MI 49855 The medial forebrain bundle (MFB) has been identified as a pleasure center in the brain. Research has demonstrated that subjects of various species would respond to produce electrical stimulation of this structure. The present study examined the effects of two commonly ingested chemical substances on the pleasure mechanism. It was hypothesized that the stimulant drug would suppress the threshold, therefore increasing the frequency of bar presses. Additionally, it was hypothesized that the depressant would increase the threshold, thus decreasing the frequency of bar presses. A stimulant, caffeine, and a depressant, alcohol, were given to rats to assess the effects these drugs would have on self-stimulatory pleasure-seeking behavior. Subjects underwent a surgical implantation of an electrode into the MFB. Each subject received 35mL of water per day. During the treatment period, the chemical variable was delivered to the subject through the water supply. A baseline period was established for each subject for com parison during the treatment period. During treatment, each subject was randomly selected to receive one of the variables. Treatment lasted a period of four weeks with the subject tested biweekly. Histologies were performed on each subject to determine the exact location of the implanted electrode.