Selective serotonin receptor stimulation of the medial nucleus accumbens differentially affects appetitive motivation for food on a progressive ratio schedule of reinforcement.
Previously, we reported that stimulation of selective serotonin (5-HT) receptor subtypes in the nucleus accumbens shell differentially affected consumption of freely available food. Specifically, activation of 5-HT(6) receptors caused a dose-dependent increase in food intake, while the stimulation of 5-HT(1/7) receptor subtypes decreased feeding [34]. The current experiments tested whether similar pharmacological activation of nucleus accumbens serotonin receptors would also affect appetitive motivation, as measured by the amount of effort non-deprived rats exerted to earn sugar reinforcement. Rats were trained to lever press for sugar pellets on a progressive ratio 2 schedule of reinforcement. Across multiple treatment days, three separate groups (N=8-10) received bilateral infusions of the 5-HT(6) agonist EMD 386088 (at 0.0, 1.0 and 4.0 μg/0.5 μl/side), the 5-HT(1/7) agonist 5-CT (at 0, 0.5, 1.0, or 4.0 μg/0.5 μl/side), or the 5-HT(2C) agonist RO 60-0175 fumarate (at 0, 2.0, or 5.0 μg/0.5 μl/side) into the anterior medial nucleus accumbens prior to a 1-h progressive ratio session. Stimulation of 5-HT(6) receptors caused a dose-dependent increase in motivation as assessed by break point, reinforcers earned, and total active lever presses. Stimulation of 5-HT(1/7) receptors increased lever pressing at the 0.5 μg dose of 5-CT, but inhibited lever presses and break point at 4.0 μg/side. Injection of the 5-HT(2C) agonist had no effect on motivation within the task. Collectively, these experiments suggest that, in addition to their role in modulating food consumption, nucleus accumbens 5-HT(6) and 5-HT(1/7) receptors also differentially regulate the appetitive components of food-directed motivation.
Department of Psychology, Wake Forest University, Winston-Salem, NC 27109, USA. prattwe@wfu.edu
Wayne E
WE
Pratt
Megan A
MA
Schall
Eugene
E
Choi
D000818:Animals; D003216:Conditioning, Operant; D004435:Eating; D005021:Ethylamines / Q000494:pharmacology; D005247:Feeding Behavior / Q000502:physiology*; D007211:Indoles / Q000494:pharmacology; D008297:Male; D009042:Motivation; D009714:Nucleus Accumbens / Q000378:metabolism / Q000502:physiology*; D011725:Pyridines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D044405:Receptor, Serotonin, 5-HT2C / Q000378:metabolism; D011985:Receptors, Serotonin / Q000378:metabolism*; D012055:Reinforcement Schedule; D058825:Serotonin 5-HT1 Receptor Agonists / Q000494:pharmacology; D017366:Serotonin Receptor Agonists / Q000494:pharmacology
C534240:5-chloro-2-methyl-3-(1,2,3,6-tetrahydro-4-pyridinyl)-1H-indole; D005021:Ethylamines; D007211:Indoles; D011725:Pyridines; D044405:Receptor, Serotonin, 5-HT2C; D011985:Receptors, Serotonin; C103848:Ro 60-0175; D058825:Serotonin 5-HT1 Receptor Agonists; D017366:Serotonin Receptor Agonists; C097216:serotonin 6 receptor; C104425:serotonin 7 receptor