EFFECTS OF HALLUCINOGENS ON LOCOMOTOR AND INVESTIGATORY ACTIVITY AND PATTERNS - INFLUENCE OF 5-HT2A AND 5-HT2C RECEPTORS

The 5-HT2A and 5-HT2C antagonists MDL 100,907 and SER-082 were tested with the 5-HT2A/C agonist DOI and the 5-HT1A/2A/2C agonist LSD in the Behavioral Pattern Monitor, which provides multiple measures of locomo tor and investigatory activity. Previous investigations have shown tha t these measures load onto three independent behavioral factors: amoun t of activity, exploratory behavior, and behavioral organization. Rats pretreated with saline, MDL 100,907 (0.25-2.0 mg/kg), ol SER-082 (0.5 -1.0 mg/kg) were treated with saline, 0.25 mg/kg DOI, or 60 mu g/kg LS D. All effects of DOI were blocked by all doses of MDL 100,907, but on ly by the highest close of SER-082. While the effects of LSD on activi ty and exploratory behavior were largely unaffected, either pretreatme nt antagonized the effects of LSD on behavioral organization. Thus, al l of these effects of DOI were attributable to 5-HT2A receptors, where as the effect of LSD on behavioral organization was influenced try bot h 5-HT2A and 5-HT2C receptors. (C) 1998 American College of Neuropsych opharmacology. Published by Elsevier Science Inc.