The Journal of Neuroscience, December 1, 2000, 20(23):8861-8867
Brain-Stimulation Reward Thresholds Raised by an Antisense
Oligonucleotide for the M5 Muscarinic Receptor Infused near Dopamine
Cells
John S.
Yeomans1,
Junichi
Takeuchi1,
Marco
Baptista1,
Donna D.
Flynn2,
Karen
Lepik1,
Jose
Nobrega1,
James
Fulton1, and
Martin R.
Ralph1
1 Department of Psychology, University of Toronto,
Toronto, Ontario, Canada M5S 3G3, and 2 Department of
Molecular and Cellular Pharmacology, University of Miami School of
Medicine, Miami, Florida 33101
Oligonucleotides targeting M5 muscarinic receptor mRNA were infused
for 6 d into the ventral tegmental area of freely behaving rats trained to bar-press for lateral hypothalamic stimulation. The
bar-pressing rate was determined at a range of frequencies each day to
evaluate the effects of infusions on reward. M5 antisense oligonucleotide (oligo) infusions increased the frequency
required for bar pressing by 48% over baseline levels, with the
largest increases occurring after 4-6 d of infusion. Two control
oligos had only slight effects (means of 5 and 11% for missense and
sense oligos, respectively). After the infusion, the required frequency shifted back to baseline levels gradually over 1-5 d. Antisense oligo
infusions decreased M5 receptors on the ipsilateral, but not the
contralateral, side of the ventral tegmentum, as compared with a
missense oligo. Therefore, M5 muscarinic receptors associated with
mesolimbic dopamine neurons seem to be important in brain-stimulation reward.
Key words:
M5; muscarinic; cholinergic; dopamine; self-stimulation; reward; oligodeoxynucleotide
Copyright © 2000 Society for Neuroscience 0270-6474/00/20238861-07$05.00/0