Activity and Responsivity in Rats after Magnesium Pemoline Injections

Abstract

Rats injected intraperitoneally with magnesium pemoline avoided a buzzing sound (conditioned stimulus) associated with an electric shock to the feet (unconditioned stimulus) more frequently than controls. Drug-injected rats did not avoid the foot shock more frequently than controls, although the experi mental rats did have shorter response latencies fn the active avoidance task. In sub sequent experiments which measured activity changes and response to the buzzing sound alone, it was found that magnesium pemoline caused a lesser decrease in activity level and a more sustained responsivity to the buzzer's. sound than did control injections of tragacanth. This may account for the latency differences observed in the avoidance task.

Magnesium pemoline: Effects on spontaneous activity, stimulus responsivity and food intake

“…We did not obtain a significant interaction of Buzzer Effects by Drug Treatments by Hours, indicating that the groups did not adapt differentially to the buzzer over the 22 h. That is, MgPe did not increase or maintain stimulus responsivity in a situation where the buzzer occurs without any contingencies-i.e. , did not signal an impending change in the environment, such as shock.4 This is in contrast to the conclusions of Beach & Kimble (1967) that MgPe Ss maintain responsivity whereas controls show habituation. However, a visual examination of their data suggest that if baseline activity (pre-buzzer activity level) is taken into consideration, the controls show as much initial responsivity to the buzzer onset as MgPe animals.…”

Magnesium pemoline: Different effects with different subject stocks

“…At the human level, the controversy has concerned both the existence and explanation of the effects of MP (Smith, 1967), while at the animal level, the problem has been primarily one of explanation. At the animal level, the explanation proposed by Plotnikoff (1966) was in terms of enhancement oflearning and memory, while other workers (Frey & Polidora, 1967;Beach & Kimble, 1967) have proposed that MP produced behavioral effects by reducing the tendency to freeze or, similarly, by energizing or stimulating the S. Between these general c1asses of explanation, it seems that a much stronger case can be made for MP having a stimulating Psychon. Sei., 1969, Vol.…”

“…This dose has been weil established (plotnikoff, 1966;Beach & Kimble, 1967) as being within the effective range for producing behavioral effects, and this was the only dose level used in a subsequent study by Frey & Polidora (1967) which showed clear behavioral effects on Sprague-Dawley rats.…”

Magnesium pemoline: Effects on avoidance conditioning mediated by anticipatory responses

“…The drug had parallel effects on conditioned ("anticipatory") Recently there has been a flurry of studies investigating the effects of magnesium pemoline on avoidance acquisition, the primary reason being the reported effect of this drug on the systems that synthesize brain nucleic acid (Glasky & Simon, 1966). There now is a consensus that magnesium pemoline often facilitates avoidance acquisition in a variety of apparatuses (e.g., Beach & Kimble, 1967;Filby, Szara, & Salzman, 1967;Frey & Polidora, 1967;Plotnikoff, 1966). However, the mechanism through which this effect is mediated is not clear.…”

“…Some feel that, rather than affecting learning processes, the drug increases general "activity level" or interferes with the "freezing" behavior which frequently accompanies application of aversive stimuli. Existing data (Beach & Kimble, 1967;Boitano & Boitano, 1967) show clearly that magnesium pemoline does lead to increases in general activity level and responsivity to a buzzer stimulus-which has frequently served as the conditioned stimulus in avoidance studies.…”