Single dose and cross tolerance studies of beta-phenethylamine, d-amphetamine and LSD in the chronic spinal dog

The effects of beta-phenethylamine (PEA), d-amphetamine and LSD were studied on spinal reflexes, autonomic signs, and behavior in the non-tolerant and LSD tolerant (30 microgram/kg/day) chronic spinal dog. LSD (10 microgram/kg) facilitated the flexor reflex, produced the stepping reflex, increased respiration, pulse rate and temperature, slightly dilated pupils and produced whining, tracking and restlessness. Direct tolerance developed to all of these effects except temperature. PEA (0.8 mg/kg/min infused for 12 min) and amphetamine (3.2 mg/kg) facilitated the flexor reflex, increased respiration, temperature and the skin twitch reflex latency, caused a marked mydriasis, retracted the nictitating membrane and produced restlessness and stereotypic head movements. PEA but not amphetamine elicited stepping, and only amphetamine consistently slowed heart rate. No cross tolerance to the physiologic or behavioral effects of amphetamine was observed. Partial tolerance developed only to the actions of PEA on the stepping reflex and the nictitating membrane. The single dose effects and the lack of cross tolerance to amphetamine and PEA suggest modes of action different from LSD. PEA has some actions which differ from those of amphetamine.