Comparison Of Affective Analgesia And Conditioned Place Preference Following Cholinergic Activation Of

COMPARISON OF AFFECTIVE ANALGESIA AND CONDITIONED PLACEPREFERENCE FOLLOWING CHOLINERGIC ACTIVATION OFVENTRAL TEGMENTAL AREA SUBREGIONSby ELENA SCHIFIRNEŢDecember 2010Advisor: Dr. George S. BorszczMajor: Psychology (Behavioral & Cognitive Neuroscience)Degree: Doctor of PhilosophyActivation of the dopaminergic mesolimbic reward circuitry that originates in the ventraltegmental area (VTA) is postulated to preferentially suppress affective reactions to noxiousstimuli (affective analgesia, AA). VTA dopamine neurons are activated via cholinergic inputs,and we have observed that microinjections of the acetylcholine agonist carbachol suppressedvocalizations of rats that occur following administration of brief (1 sec) tail-shocks (vocalizationafterdischarges = VAD). VADs are a validated rodent model of pain affect. In addition, thecapacity of carbachol to support reinforcement appears to be regionally dependent within VTA.Ikemoto & Wise (2002) reported that carbachol was self-administered in the posterior VTA (pVTA), but not the anterior VTA (aVTA). We have previously reported that carbachol preferentially increased the threshold current intensity for eliciting VADs in aVTA and pVTA,but not midVTA. This carbachol-induced AA is mediated by muscarinic receptors within thepVTA and by both muscarinic and nicotinic receptors within the aVTA. Using the conditioned place preference paradigm (CPP), the present study evaluated the muscarinic versus nicotinicinvolvement in intra-VTA carbachol-induced CPP learning by administering atropine