No abstract

STRETCH, W., GERBER, G. J., and WOOD, S. h4. 1971. Factors affecting behavior maintained by response-contingent intravenous infusions of amphetamine in squirrel monkeys. Can. J. Physiol. Pharmacsl. 49,[581][582][583][584][585][586][587][588][589] Behavior developed and maintained in previously untrained monkeys by a modified progressive-ratio schedule of response-contingent intravenous infusions of d-amphetamine is described. Availability of amphetamine infusions can be restricted to relatively brief (2 h) daily sessions, once responding has been established, without disruption of self-administration behavior. When amphetamine infusions are replaced by saline, responding is reduced immediately to a low rate; when amphetamine infusions are replaced by saline ern$ the session is preceded by an intramuscular injection of the drug 4 1.5 mg/kg), the pattern of responding is indistinguishable from that observed when drug infusions are available. If an external discriminative stimulus, normally associated with those periods in which infusions are available, is withdrawn, responding is reduced to a low rate. The discriminative stimulus entered into control of the behavior only when amphetamine had been administered by intravenous infusion or by intramuscular injection beforehand, reflecting, therefore. some form of 'state dependence'. Possible sources of interoceptive stimaalation, arising from an infusion per se, did not controI behavior to any significant extent. Results emphasize the need for specific control procedures when drug self-administration is to be conceptualized as an operant reinforcement effecf . STRETCH, R., GEHUER, G . J., et WOOD, S. M. 1971. Factors affecting behavior maintained by response-contingent intravenous infusions of amphetamine in squirrel monkeys. Can, J. Fahysiol. Pharmacol. 49,581-489.Nous dtcrivons le cormportenlent induit et entretenu, chez des singes antirieurernent nonentraints, par des infusions i.v. de d-aanphCtamine. kin certain nornl-?re de riponses, suivant une Cchelle de raison progressive. est requis pour les infusions successives. Une fois la rkpoaase ttablie, la session &auto-administration peut &re ramen& B une durke relativement br&e (2 h ) , sans affecter Ie conditionnera~ent.Quand les infusions d'amphCtamine sont rernplacbes par des infusions de salin, le taux de rkponse diminue irnrnCdintement.Qraand les infusions d1arnph6tarnime sont remplact5es par des infusions de salin, et que Pa session est prkctdke par une injection i.m. d':arnphbtamine ( 1 "5 mg/kl), Ie mode de riponse n9sst pasddiffCrent de celui observk avec des infusions d'amphbtarnine.Si un stimulus discrirninatif exkerne norn~alemcnt associt? aux pCriodss ct'auto-infamsion, est supprirnb, 16 taux de reponse diminue.ke sti~raulus discriminatif paemant part au contr81e du comporternent seulement quand Iqamp&Ctamine est administrke par infusion i.v. ou injection prCa%able i.m.. refikte dons une certaine forme 'Wst'at de d@pemdance9'. Ides stimulations interoceptives, asssciies h l'infusion elle-meme, n'affectent...

Following extinction of a drug-reinforced operant, intravenous pre-treatment with d-amphetamine before commencement of each daily session in an extended series led to consistent reinstatement of the characteristic pattern of drug self-administration behaviour. The effect depended partially upon the amphetamine dose used as a pretreatment. Results from related experiments, in addition to the present one, suggest that a complex relationship between external discriminative stimuli and amphetamine pretreatment forms the basis for drug-induced reinstatement of self-administration behaviour. A "state-dependent" learning process may also be implicated.

After stabilization of response rates engendered by a free-operant avoidance contingency, the lever-pressing of two squirrel monkeys was maintained for several months by a fixed-interval schedule of electric shock presentation. Initially, response-contingent shocks produced substantial increases in response rates. Continued exposure to the schedule resulted in a reduced overall rate accompanied by a change in the temporal patterning of responses. There was a pause in responding after most shock deliveries; the rate of responding then increased during the interval to reach a terminal value preceding shock presentation. Omission of shocks for part of the daily session led to higher rates of responding; the reintroduction of response-contingent shocks produced a lower overall rate and reinstated the temporal patterning of responding characteristic of the fixed-interval schedule.

Rates of lever pressing, maintained either by response-dependent intravenous injections of cocaine (250 mug/kg per injection) or by food-pellet presentation, were compared and found to vary systematically as a function of the delay (5-100 s) imposed between the response(s) and the occurrence of reinforcement. The control of responding by two schedules of delayed reinforcement was studied. The first scedule permitted responses to occur during the delay period without any programmed consequence; the second schedule required a response, and then the elapse of x seconds without any additional response(s). At imposed delays of 50 and 100 s, response rates were reduced significantly when the second schedule was in effect by comparison with the first. The effect was observed when responding was maintained either by intravenous cocaine injections or by food-pellet presentation. Across all comparable conditions, response rates were higher when maintained by scheduled cocaine injections than by food pellets. Rate enhancement, generally induced by drugs of the psychomotor stimulant type, could account for the observed difference.