Jack Pearl

Effects of opiates and opiate antagonists on the Straub tail reaction in mice

1 . Subcutaneous injections of opiates produced the Straub tail reaction in mice. The potencies of the opiates in mice were consistent with previous estimates of the analgesic potencies in animals and in man. 2 . The potencies of sixteen antagonists in counteracting the reaction were consistent with those previously obtained with the rat tail‐flick test. 3 . The (–) isomers of four benzomorphan derivatives were much more potent in counteracting the reaction than their (+) isomers and about twice as potent as their racemates. The activity of the isomers seemed to follow Pfeiffers rule: the lower the effective dose of a drug, the greater the difference in the pharmacological effects of the optical isomers. One of the trans isomers acted like an opiate, while its cis isomer acted like an antagonist. 4 . Naloxone and nalorphine fulfilled conventional criteria for competitive antagonism, whereas atropine and the (–) and the (+) isomers of pentazocine and of cyclazocine did not do so. 5 . The Straub tail test seems to be useful for studying structure‐activity relations among opiates and opiate antagonists.

Avoidance box for mice.

Abstract An inexpensive and easily constructed apparatus for training mice to quickly acquire an avoidance response is described. Mice are trained to jump on a platform and are automatically returned to the grids.

Better discriminated bar-press avoidance at short intertrial intervals

Four groups of rats received discriminated avoidance training in Skinner boxes at intertrial intervals (ITIs) of 0.2, 1, 5, or 30 sec. As ITI decreased avoidances and bar presses per min. increased and differences among groups persisted when ITI was then increased to 30 sec. for all groups. The better avoidance at short ITIs was attributed to response perseveration after shock and the results were related to those obtained without an exteroceptive warning stimulus (Leaf, 1965) and to those with discontinuous shock (D’Amato, Keller, & Di-Cara; 1964; Hurwitz, 1964).

Similarities in effects of barbiturates and mild tranquilizers on activity in mice

To determine the extent of similarity in the effects of barbiturates and mild tranquilizers on motor activity, mice were given pentobarbital, phenobarbital, meprobamate, and chlormezanone over a wide range of doses. All drugs increased spontaneous motor activity in photocell units at low doses and decreased activity at higher doses. The drugs resembled each other in producing the same pattern of motor impairment. Ataxia was noted at intermediate doses, and impairment of the righting reflex and ptosis were noted at higher doses. Mention was made of the possible relationship of motor impairment to changes in spontaneous activity and to changes in performance with different schedules of reinforcement.

Drugs and avoidance performance

Cocaine and pipradrol facilitated the avoidance performance of rats in Skinner boxes. When the drugs were withdrawn performance deteriorated to levels shown by rats that had never been drugged. The drugs seemed to temporarily affect either emotionality or activity rather than to permanently affect learning. Tricyanoaminopropene did not affect performance.

Effects of morphine and nalorphine on the phenylquinone-induced syndrome in monkeys

SummaryIntraperitoneal injection of 6 mg/kg of phenyl-p-quinone produced a syndrome consisting of distorted limb and body positions in rhesus monkeys. Intramuscular injection of 1 mg/kg of morphine abolished the syndrome, whereas 16 mg/kg of nalorphine had no appreciable effects on the syndrome. One-half mg/kg of nalorphine reversed the inhibitory effects of 1 mg/kg of morphine on the syndrome.

Differences in antiwrithing activity of morphine and nalorphine over time and in slopes of the dose-response lines

SummaryWrithing was produced in mice by injecting them intraperitoneally with phenylquinone either 10 or 20 min before the start of scoring. The activity of two antiwrithing agents was compared: morphine and nalorphine at doses of 0.5 and 2.0 mg/kg injected subcutaneously 10, 20, or 40 min before scoring. Analyses of both quantal and graded data indicated that the antiwrithing activity of nalorphine decreased faster than that of morphine over time and that the slopes of the dose-response lines for nalorphine were flatter than those for morphine.

Effect of apomorphine and its N-propyl homologue on ethanol withdrawal head twitches in mice.

Collier, Hammond & Schneider (1976) reported that apomorphine, given orally, decreased the incidence of head twitches induced by ethanol withdrawal. These results were confirmed in the present study. Moreover, the N‐propyl homologue of apomorphine was about 45 times more potent than apomorphine in affecting head twitching.