Knockdown of the type 2 and 3 inositol 1,4,5-trisphosphate receptors suppresses muscarinic antinociception in mice.

The involvement of central endoplasmic inositol 1,4,5-trisphosphate receptors (IP3R) in muscarinic antinociception was investigated in the mouse hot plate test. Selective knockdown of type 1, 2 and 3 IP3R was obtained by means of an antisense oligonucleotide (aODN) strategy. A selective IP3R protein level reduction of approximately 30– 50% produced by aODN administration for each receptor subtype investigated was demonstrated by Western blotting experiments. I.c.v. pretreatment with an aODN complementary to the sequence of the type 2 IP3R (0.1–3 nmol per mouse i.c.v.) prevented the antinociception induced by physostigmine (0.15 mg kg1 s.c.) and oxotremorine (60 g kg1 s.c.). Similarly, an aODN against type 3 IP3R (0.1–3 nmol per mouse i.c.v.) antagonized cholinergic antinociception. A shift to the right of the physostigmine dose–response curve was obtained after anti-type 2 IP3R2 and anti-type 3 IP3R treatments. Conversely, pretreatment with an aODN complementary to the sequence of type 1 IP3R (0.1–5 nmol per mouse i.c.v.) did not modify the antinociception induced by physostigmine and oxotremorine. Mice undergoing treatment with aODNs did not show any impairment of the locomotor activity, spontaneous motility and exploratory activity as revealed by the rota-rod and hole board tests. These results indicate a selective involvement of type 2 and 3 IP3R in central muscarinic antinociception in mice.