Thomas A. Ban: Psychopharmacology. Baltimore: Williams and Wilkins; 1969

Leon S. Morra’s Extracts - 9

Part One, Chapter Two: Animal Pharmacology


3. Conditioning Procedures

“In assessing presently available psychoactive drugs there are three basically different stimulus-response constellations which are frequently examined. These are the unconditional reflex [UR], which is an innate specific response to a particular stimulus; the conditional reflex [CR], which is an acquired specific response to a formerly unspecific stimulus; and the orienting reflex [OR], originally conceived as a startle response…"

Unconditional reflex activity is differentially influenced by psychoactive drugs… psychostimulant drugs in general have a facilitating (strengthening) effect on the motor component of the responses… On the other hand, sedatives (and also hypnotics) have an inhibiting influence…"

The effects of psychoactive drugs on conditional reflex activity can be studied by… the classical or Pavlovian conditioning paradigm, the instrumental conditioning paradigm and the ‘experimental neurosis’ model."

 “Classical paradigm. Stimulants, e.g., caffeine and amphetamines facilitate CR formation. On the other hand, sedatives, as for example barbiturates interfere with CR formation only in such doses, which also interfere with the UR. Anxiolytics appear to have only little or no effect on the motor component of the conditional withdrawal reaction reflex whereas they diminish the autonomic (cardiac) component of the same reaction. The effect of various antipsychotic drugs on CR behavior had been, extensively studied. It was recognized that that the phenothiazine, chlorpromazine, has a marked inhibitory effect on the motor component of the conditional withdrawal reflex [whereas] it affects the concomitant autonomic (cardiac) components to a much lesser extent."

Instrumental paradigm. In contradistinction to the classical paradigm in which the association of the conditional stimulus with the unconditional stimulus is the prerequisite to establish a CR, in the instrumental paradigm it is the association of the response with a motivational factor (reward or punishment) which is the most important for acquisition…"

“…stimulants, e.g., caffeine, amphetamine and 2-benzylpiperidines, enhance operant avoidance and approach reactions [whereas].sedatives, e.g., barbiturates, have a decreasing effect on operant behavior. Lever pressing avoidance responses, with the use of the Sidman avoidance schedule increased, under the influence of thymoleptic (antidepressant) drugs. Among the anxiolytic substances …an increment in lever pressing avoidance responses was found after the administration of benzodiazepines compounds… The prevailing characteristic with antipsychotic properties in the instrumental paradigm is their ability to depress operant behavior."

Experimental neurosis.[Pavlov] recognized that neuroses with predominantly excitatory manifestations could be [successfully] treated only by sedatives, e.g. bromides, [whereas] those neuroses with prevailing inhibitory manifestations the administration of caffeine, a stimulant, seemed to be quite useful."

Orienting reflex.The inhibitory effect of CNS stimulants were reported. Antidepressants and anxiolytic drugs do not seem to exert any characteristic influence’ The depressant effect of antipsychotics were demonstrated… Both chlorpromazine and reserpine diminished the motor (centrally mediated skeletal muscle) and cardiac (autonomic) components of the orienting reflex.”


León S. Morra

April 6, 2017