RNA interference-mediated silencing of Kv7.2 in rat dorsal root ganglion neurons abolishes the anti-nociceptive effect of a selective channel opener.

INTRODUCTION

Development of agonistic analgesic drugs requires proof of selectivity in vivo attainable by selective antagonists or several knockdown strategies. The Kv7.2 potassium channel encoded by the KCNQ2 gene regulates neuronal excitability and its activation inhibits nociceptive transmission. Although it is a potentially attractive target for analgesics, no clinically approved Kv7.2 agonists are currently available and selectivity of drug candidates is hard to demonstrate in vivo due to the expenditure to generate KCNQ2 knockout animals and the lack of Kv7.2 selective antagonists. The present study describes the set-up of an RNA interference-based model that allows studying the selectivity of Kv7.2 openers.

METHODS

Adeno-associated virus (AAV) vectors were used to deliver the expression cassette for a short hairpin RNA targeting KCNQ2. Heat nociception was tested in rats after intrathecal AAV treatment.

RESULTS

Surprisingly, screening of AAV serotypes revealed serotype 7, which has rarely been explored, to be best suited for transduction of dorsal root ganglia neurons following intrathecal injection. Knockdown of the target gene was confirmed by qRT-PCR and the anti-nociceptive effect of a Kv7.2 agonist was found to be completely abolished by the treatment.

DISCUSSION

We consider this approach not only to be suitable to study the selectivity of novel analgesic drugs targeting Kv7.2, but rather to serve as a general fast and simple method to generate functional and phenotypic knockdown animals during drug discovery for central and peripheral pain targets.