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F C Colpaert

Publications and source records attributed to F C Colpaert.

At least 145 records · Page 8Linked to original sources
PubMed1983

Effects of dorsal raphe stimulation on escape induced by medial hypothalamic or central gray stimulation.

Electrical stimulation of the ventral part of the mesencephalic central gray affects escape responding induced by stimulation of either the medial hypothalamus (MH) or dorsal central gray (CG) in the rat. The sign and magnitude of the effect appeared to depend on the following factors: (1) The location of the site stimulated in the ventral central gray and the intensity of the stimulation. A stimulation of the dorsal raphe nucleus (DR) which induced a marked rewarding and a low aversive effect reliably suppressed MH or CG induced escape. Stimulation of sites located at the boundary between DR and central gray enhanced escape at low intensities and suppressed it at higher intensities. When located more laterally in the ventral central gray, the stimulation induced less rewarding and more marked aversive effects and it reliably enhanced MH or CG induced escape. (2) The kind of stimulation applied (monopolar or bipolar). (3) The location of the site (MH or CG) from which the stimulation-induced escape responses were obtained.

Animals↗
PubMed1982

Increased naloxone reversibility in fentanyl dose-dose discrimination.

Two groups of rats were trained to discriminate 0.04 mg/kg of fentanyl from saline (drug-saline discrimination) or from 0.02 mg/kg of fentanyl (dose-dose discrimination). The ED50 of naloxone for antagonizing the discriminative effects of 0.04 mg/kg fentanyl was 0.05 and 0.0062 mg/kg, respectively. This 8.1 fold difference in naloxone reversibility suggests that dose-dose discrimination yields higher pharmacological specificity than the commonly used drug-saline discrimination.

Animals↗
PubMed1982

Further evidence validating adjuvant arthritis as an experimental model of chronic pain in the rat.

The experiments described here were aimed at further validating adjuvant arthritis as an animal model of chronic pain. It was found that the relative oral intake of a 0.008 mg/ml solution of fentanyl was higher in arthritic than in normal control rats; this difference was predicted by the notion that the analgesic effect of a substance may reinforce its intake in animals exposed to pain, more so than in normal pain-free animals. It was also found that body weight decreases and that vocalizations of aggregated rats increase as a result of the challenge; these effects suggest that the vegetative signs and the behavioral irritability which are characteristic of chronic pain in humans, also occur in arthritic animals. The pain which thus seems to be associated with adjuvant arthritis was estimated to have its onset on days 10-11, to peak on days 18-21, and to terminate on days 35-40 after inoculation with Mycobacterium butyricum.

Animals↗
PubMed1982

OR discrimination: a new drug discrimination method.

Rats were trained to respond on one of two levers for food (drug lever) after injections of either 0.04 mg/kg fentanyl or 10 mg/kg cocaine HCl, and to respond on the saline lever after saline injections. The acquisition data indicate that this OR discrimination is feasable in the rat, though it developed slowly due to a bias of responding on the drug lever. The generalization data obtained here suggest that the OR discrimination method may establish relations between the cuing properties of drugs which are not apparent with the commonly used drug-saline method of drug discrimination.

Animals↗
PubMed1982

Parametric effects in the discrimination of intracranial stimulation: some methodological and analytical issues.

Rats were implanted with electrodes in the medial forebrain bundle at the level of the lateral hypothalamus. Electrical stimulation was established as a conditioned stimulus for responding in a modified two-way active shock avoidance procedure. Stimulus generalization experiments were conducted to determine the effects of pulse frequency, current intensity, pulse duration, and of train duration. It was found that the discriminative stimulus properties of the electrical stimulation co-varied in an orderly manner with variations in each of the parameters. The generalization data sets of frequency, intensity, and train duration could be fitted by linear functions in log-linear coordinates; the effects of pulse duration generated a biphasic gradient. An analysis in terms of charge revealed that train duration had the lowest slope, whereas frequency and intensity generated equally steep functions. The most striking differences occurred among conditions which were similar in terms of current intensity, pulse duration and number of pulses, but which differed in the temporal patterning of pulses. Some methodological and analytical aspects of discrimination and generalization with intracranial stimulation are discussed.

Animals↗
PubMed1982

Factors regulating drug cue sensitivity: the effects of dose ratio and absolute dose level in the case of fentanyl dose-dose discrimination.

This study presents a parametric analysis of the difference case in drug discrimination; rats were trained to discriminate a higher training dose of fentanyl, a narcotic analgesic, from a lower dose. Two parameters of dose-dose discrimination were investigated. First, dose ratio indicates the magnitude of the difference, expressed as a ratio, between the higher and the lower of the two training doses; dose ratios were 2, 4, 8, and 16 in four groups of animals. The second parameter is the absolute level of fentanyl dose at which any given ratio can be discriminated; in all four groups, the higher of the two training doses was progressively lowered from 0.04 to 0.00125 mg/kg. It was found that dose-dose discriminability of fentanyl was proportional to dose ratio in the entire 2 to 16 range of dose ratio, and that discriminability decreased monotonically as the absolute dose level was lower. Bias in discriminative responding was determined by absolute dose level only; dose ratio exerted no effect. The slope of the fentanyl generalization gradient increased as the dose ratio was smaller, and decreased as the absolute dose level was lower. Both dose ratio and absolute dose level also exerted effects on the ED50-value, but the effects of dose ratio were apparent only at higher training doses of 0.04 to 0.01 mg/kg. The data are consistent with the suggestion that fentanyl-saline discrimination is a special case of dose-dose discrimination; it is similar to the case where the higher of two training doses differs about 16-fold from the lower one. At this point, the lower training dose produces only liminal effects.

Animals↗
PubMed1981

Long term catheterization of the lumbar epidural space in rats.

This note describes a simple technique for the administration of drug solutions into the lumbar epidural space of the unanesthetized and freely moving rat. A poly-ethylene (PE-10) catheter is inserted into the epidural space through a hole in the third lumbar vertebra, and subcutaneously tunneled towards the neck region. The implantation procedure is well-tolerated, and repeated saline injections over a prolonged period of time were found not to exert any deleterious effect on the animals' apparent health or gross behavior. The viability of the technique is demonstrated in an experiment on the effect of injection volume on the analgesic action of epidurally administered fentanyl.

Analgesia↗
PubMed1981

Factors regulating drug cue sensitivity: the effect of frustrative non-reward in fentanyl-saline discrimination.

In this study, rats were trained to discriminate 0.04 mg/kg of fentanyl from saline in two-lever food-reinforced procedure. The study examined the effects of a manipulation of reinforcement (i.e. frustrative non-reward; FNR) on several characteristics of fentanyl-saline discrimination. It was found that asymmetrical FNR in either saline or drug sessions retarded the acquisition of the discrimination and codetermined response bias; symmetrical FNR in both types of sessions had no effect. Asymmetrical FNR in saline sessions steepened the slope of the generalization of fentanyl, but also of morphine and sufentanil; asymmetrical FNR in drug sessions flattened the gradient's slope. Symmetrical FNR had effects on slope which were similar to those of asymmetrical FNR in saline sessions. Both symmetrical and asymmetrical FNR also appeared to affect the ED50-value of different agonists, and the ED50-value of naloxone in antagonizing 0.04 mg/kg of fentanyl. It thus appears that reinforcement plays a major role in the acquisition of fentanyl-saline discrimination and in the quantitative characteristics of the stimulus generalization gradient of fentanyl and other agonists. It is also suggested that the training drug itself may interact with the effects of FNR on its own gradient.

Animals↗
PubMed1980

Evidence that a preferred substrate for type B monoamine oxidase mediates stimulus properties of MAO inhibitors: a possible role for beta-phenylethylamine in the cocaine cue.

In the experiment, rats were trained to discriminate 5 mg/kg cocaine HCl from saline in a two-bar drug discrimination procedure. Stimulus generalization experiments were carried out with six inhibitor drugs of monoamine oxidase. The rank order of absolute potency of these drugs in inducing stimulus generalization with cocaine was: tranylcypromine (ED50 in mg/kg; 1.2)>pheniprazine (3.5)>deprenyl (5)>pargyline (28)>nialamide (approximately 170); at up to 40 mg/kg, clorgyline failed to produce 50% generalization. All six drugs also potentiated tryptamine in producing body tremors and clonic seizures, the rank order of potency being tranylcypromine (0.081)>clorgyline (0.14) greater than or equal to pheniprazine (0.15)>pargyline (1.97)>deprenyl (15.5)>nialamide (18.7). Tryptamine is a common substrate for both type A and type B monoamine oxidase, so that tryptamine potentiation may serve to determine the relative specificity of the doses at which the inhibitor drugs generalized with cocaine. The present data may suggest that endogenous substances which are preferred substrates for type B monoamine oxidase in rat brain can exert control of behavior by virtue of cocaine-like stimulus properties. beta-Phenylethylamine, more so than dopamine, appears to be candidate substance for mediating the discriminative stimulus properties of cocaine and, perhaps, of other central nervous system stimulants.

Animals↗
PubMed1979

In vivo evidence of partial agonist activity exerted by purported 5-hydroxytryptamine antagonists.

Using a food-reinforced two-lever operant method, rats (n = 9) were trained to discriminate 0.16 mg/kg LSD from saline. Tests for stimulus generalization in rats so trained indicated that the purported 5-HT antagonists cyproheptadine (1.25 and 10 mg/kg), methysergide (0.16 to 10 mg/kg) and mianserin (2.5 to 40 mg/kg) produced partial generalization with LSD. The hallucinogens mescaline (5 to 40 mg/kg) and quipazine (1.25 to 5 mg/kg) were also generalized with LSD. The data suggest that cyproheptadine, methysergide and mianserin may produce partial agonist effects in addition to their antagonist action at central 5-HT receptor sites.

Animals↗