Antisense Knockdown of Brain Dopamine Receptors

Abstract

Publisher Summary Antisense knockdown refers to the ability of specifically designed short sequences of antisense oligodeoxynucleotides (AON) to bind to their complementary mRNA and stop translation, thereby preventing the production of the protein that the mRNA codes for. Because it is so highly specific, it can be used to probe the functions of receptor subtypes for which specific and selective agonists or antagonists do not exist. This chapter describes the electrophysiological consequences following antisense knockdown of dopamine D2 and/or D3 receptors in DA substantia nigra (SN) neurons. In this purpose male Sprague-Dawley rats were anesthetized with ketamine-xylazine, placed in a stereotaxic apparatus, and implanted with a 28-g stainless steel guide cannula at a 20-degree angle. Three to 7 days after the start of the infusion, rats were anesthetized with urethane, the left femoral vein or a lateral tail vein was cannulated, and each rat was placed into a stereotaxic frame. A bipolar stimulating electrode was inserted into the ipsilateral neostriatum, and extracellular recordings of antidromically identified SN DA neurons were obtained. Studies show that although there were clear effects of both D2 and D3 AON treatment on the apomorphine dose-response relation, on the terminal excitability and on the proportion of antidromic responses consisting of the initial segment and somadendritic components, there was no effect of any AON treatment on the baseline spontaneous firing rate or pattern. The data presented in the chapter shows that DA neurons possess functional D2 and D3 autoreceptors at both their axon terminal and somatodendritic regions. Both types of terminal autoreceptors modulate terminal excitability and presumably the release of DA from the nerve terminals and/or its synthesis.