AN INVESTIGATION INTO THE EFFECTS OF APOMORPHINE ON THE RELEASE OF ACETYLCHOLINE IN THE STRIATUM OF FREELY-MOVING RAT USING IN-VIVO MICRODIALYSIS

1. Using in vivo microdialysis, we studied the effects of apomorphine on the release of acetylcholine (ACh) in the striatum of freely-moving rats, 2. Basal release of ACh was 3.01 +/- 0.51 pmol/15 min in 30 mul (containing of 10 muM neostigmine) of the striatal perfusate. 3. Ring er containing tetrodotoxin (1 muM), hemicholinium-3(5 mM), or Ca2+-fre e Ringer was perfused into the striatum. Each of these treatments prod uced a significant attenuation in release content of ACh. High K+ (30 mM) produced a significant increase in ACh release. 4. In normal rats, apomorphine (0.05 mg/kg, s.c.) increased striatal ACh release. A high dose (1.0 mg/kg) significantly attenuated release. 5. In 6-OHDA-pretr eated rats, although the lower dose of apomorphine did not increase st riatal ACh release, the high dose produced a more significant attenuat ion of release. 6. It is concluded that apomorphine enhanced or attenu ated the striatal ACh release and that this effect was regulated by ni gro-striatal dopaminergic system in the freely moving rats.