The Effect Of Morphine On Dopamine Neuron Activation In Males And Cycling Females
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The aim of this study was to evaluate the influence of estrogen on the electrophysiological response of ventral tegmental area (VTA) dopamine (DA) neurons to morphine (10 mg/kg; IP) in experimentally naïve adult male and intact adult female cycling Sprague-Dawley rats. Five groups were studied: males, proestrus females, estrus females, metestrus females, and diestrus females. Continuous 40 minute recordings were collected for each animal (5 minutes baseline, 5 minutes after a saline (0.9% NaCl) injection, and 30 minutes after morphing injection (10 mg/kg)). Results showed significant increases in VTA DA activity in the Metestrus and Male groups, no significant differences in activity in the Diestrus and Proestrus groups, and a significant decline in activity in the Estrus group after a morphine injection. Between group differences show that the Metestrus and Male group's DA activity significantly increased relative to the other groups at the corresponding time points. This study did not support the hypothesis that estrogen enhances VTA DA neuron activation following morphine administration.