The pharmacodynamic characterization of an antisense oligonucleotide against monoamine oxidase-B (MAO-B) in rat brain striatal tissue

In situ imaging of specific binding of [3H]isatin in rat brain

Isatin is an endogenous indole that influences a range of processes both in vivo and in vitro. It has a distinct and discontinuous distribution in the brain, as well as in other mammalian tissues and body fluids. However, the distribution of isatin binding sites in the brain is not known. Using a real-time beta-imager we have investigated the distribution of [3H]isatin-specific binding in rat brain sections. The highest labeling was found in hypothalamic nuclei and in the cortex, hippocampus, and cerebellum. Administration of the mechanism based monoamine oxidase inhibitor, pargyline, reduced but did not abolish the specific binding of [3H]isatin in the rat brain. The distribution became cortex, cerebellum, hypothalamus > hippocampus > brain stem > thalamus approximately striatum.

An antisense oligonucleotide targeted at MAO-B attenuates rat striatal serotonergic neurotoxicity induced by MDMA

The present study was designed to elucidate the role of dopamine (DA) metabolism in the serotonergic neurotoxicity induced by 3,4-methylenedioxymethamphetamine (MDMA). An antisense (AS) oligonucleotide (ODN) sequence targeted at monoamine oxidase-B (MAO-B) was utilized to attenuate MAO-B activity prior to MDMA administration. Sprague-Dawley rats were surgically implanted with intracerebroventricular (icv) cannulae and received a continuous infusion of MAO-B AS-ODN via an osmotic minipump. Constant AS ODN infusion for 7 days at a rate of 0.5 microl/h (total daily dose 600 pmol) resulted in a 63% knockdown of MAO-B activity. MDMA (40 mg/kg, sc) produced a rise in body temperature within 1 h of MDMA administration and a reduction in striatal serotonin (5-HT) and 5-hydroxyindole acetic acid (5-HIAA) levels 7 days later. Pretreatment with the MAO-B AS ODN prior to MDMA attenuated this reduction in serotonergic markers, yet had no effect on MDMA-induced hyperthermia. Furthermore, in vivo microdialysis revealed that previous AS ODN treatment failed to alter the acute DA release induced by MDMA (10 mg/kg, sc) within the striatum. These results indicate that MAO-B plays an integral role in the development of MDMA-induced neurotoxicity while not affecting MDMA-induced hyperthermia or acute DA release.