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EFFECTS OF ACUTE AND WEEKLY EPISODIC EXPOSURES TO ANATOXIN-A ON THE MOTOR ACTIVITY OF RATS: COMPARISON WITH NICOTINE.
Citation:
MACPHAIL, R. C., J. D. FARMER, AND K. JAREMA. EFFECTS OF ACUTE AND WEEKLY EPISODIC EXPOSURES TO ANATOXIN-A ON THE MOTOR ACTIVITY OF RATS: COMPARISON WITH NICOTINE. TOXICOLOGY. Elsevier Science Ltd, New York, NY, 234(1-2):83-89, (2007).
Impact/Purpose:
To examine the effects of Anatoxin-a, a potent nicotinic cholinergic agonist
Description:
Anatoxin-a is a potent nicotinic cholinergic agonist, that is produced by many genera of cyanobacteria, and has caused several poisoning episodes of wildlife, livestock, and domestic animals. Cyanobacterial blooms and toxin exposures are likely to occur episodically as environmental conditions enable bloom formation and dissipation. Previous research obtained tolerance and sensitization to nicotine¿s effects on the motor activity of rats when it was administered episodically at weekly intervals. Given the potent nicotinic actions of anatoxin-a, it was of interest to compare its effects with those of nicotine when given at weekly intervals. Adult male Long Evans rats were tested daily (M-F) in a photocell device, that recorded both horizontal and vertical motor activity, during 30-min sessions. Anatoxin-a and nicotine were given s.c. once a week for four weeks, just prior to a test session. Anatoxin-a was given as the (+) isomer and as the racemate. Dose ranges for each compound were: (+)anatoxin-a, 0.075-0.225 mg/kg; (+/-) anatoxin-a, 0.2-0.95 mg/kg; and (-)nicotine, 0.3-1.8 mg/kg. Each experiment also included a saline-vehicle control group. Nicotine initially decreased both horizontal activity and, to a greater extent, vertical activity. Tolerance developed to nicotine¿s effects with weekly administration. Both forms of anatoxin-a also initially decreased horizontal and vertical activity, and to roughly equivalent degrees. Neither form of anatoxin-a, however, induced tolerance with weekly administration. Thus, anatoxin-a and nicotine can be distinguished by their effects on motor activity with episodic treatment, suggesting different sites of action for the compounds in the nervous system.