Biomedical subjects

T.U.C. Järbe

Publications and source records attributed to T.U.C. Järbe.

4 recordsLinked to original sources

PubMed1995

Discriminated conditioned taste aversion for studying multi-element stimulus control.

The effects of morphine pre-treatment interval on the stimulus control exerted by a multi-element stimulus consisting of morphine (5.6mg/kg), saccharin (0.2%, w/v), and a ball-bearing drinking nozzle in a discriminated taste aversion procedure were examined. In this discriminated aversion procedure, rats received injections of LiCI following presentation of this multielement stimulus, and injections of saline following the saline, water, and non-ball-bearing nozzle composite stimulus. These paired rats were compared to unpaired rats that received saline injections rather than LiCI injections following presentation of the multi-element stimulus. Morphine pre-treatment times of 5, 10, and 20min were examined in groups of 12 paired and 6 unpaired rats. The discrimination was rapidly learned under all three pre-treatment intervals. In subsequent testing with each individual stimulus element and combinations of two stimulus elements, stimulus control was clearly exerted by both morphine and saccharin. Paired rats drank less saccharin than unpaired rats, and less saccharin than water. Similarly, paired rats drank less fluid following morphine administration than following saline administration, and less fluid than unpaired rats following morphine administration. Control by the nozzle type was also apparent in significant interactions between the nozzle and morphine or saccharin and pairing with LiCI. In general, pre-treatment time did not influence the stimulus control that developed. However, at the two shorter pre-treatment times there was some indication that a conditioned taste aversion to morphine was developing in the unpaired rats. These experiments indicate that such discriminated taste aversion procedures may be viable methods for studying the contextual control of how drugs function as discriminative stimuli, and that longer drug pre-treatment times may be desirable in such procedures.

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PubMed1993

In a low-versus high-dose drug discrimination task, random reinforcement in one drug state alters discriminative control only in that state.

This study investigated the effects of introducing random reinforcement training after a drug discrimination between 3.0 and 15.0mg/kg chlordiazepoxide had been acquired in rats; a two-lever food-rewarded operant procedure was used. Matched on the basis of dose-generalization test data, two dose-equisensitive groups were formed (A and B). Group A received 30 daily saline injections, which were followed by a random reinforcement session during which either left or right lever presses were reinforced on a probabilistic basis on each of the trials comprising a session. Group B received saline but no training or testing during this period. Subsequent testing revealed that responding conditioned to the low-dose training condition, but not to the high-dose training condition, was significantly changed in Group A. The randon reinforcement data further suggested that Group A did not discriminate saline from the low training dose. In Experiment 2, Group B of Experiment 1 was submitted to 30 random reinforcement training sessions, each preceded by a high training dose administration. Data showed that responding to the high dose, but not the low dose, was changed. For both experiments, chlordiazepoxide dose generalization following reacquisition was similar to that obtained before the random reinforcement phase. The findings indicate that the response pattern changed only for the stimulus condition present during random reinforcement. The random reinforcement manipulation did not disrupt the original discrimination between the high-and low-dose conditions.

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PubMed1989

Discriminative stimulus properties of ethanol: effects of cumulative dosing and Ro 15-4513.

A cumulative dose-testing procedure was developed to assess the stimulus control of ethanol (EtOH). This procedure was then used to examine the interaction between EtOH and the imidazobenzo-diazepine Ro 15-4513 in rats trained to discriminate between EtOH (lg/kg) and saline. Rebreathed air was used to assess concentrations of EtOH. When injected as a single dose (lg/kg), the concentration of EtOH in the breath did not differ significantly from the final concentration of the same amount administered cumulatively (0.25 + 0.25+0.5g/kg = lg/kg). Likewise, the generalization gradient of cumulatively administered EtOH did not differ from the gradient obtained when the three doses of EtOH were tested on separate days. The ED(50) values were 0.41g/kg for the cumulative, and 0.5g/kg for the separate administrations. Drug stimulus control was examined after 0.25, 0.5 and 1g/kg of EtOH. In combination with Ro 15-4513 (0.1-30mg/kg), administered 5min prior to the first dose of EtOH, a slight attenuation of the discriminative response to EtOH by Ro 15-4513 was seen with half (0.5g/kg) the training dose of EtOH. However, the slope function of the regression was fairly flat. Ro 15-4513 did not significantly change stimulus control induced by 0.25 and 1g/kg of EtOH. Response-times were significantly longer as a function of Ro 15-4513 dose, particularly during the first test.

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PubMed1989

Latent learning in a radial arm maze following neonatal dopamine depletion.

Animals neonatally depleted of dopamine show decreases in exploratory behaviour. As latent learning may depend on exploratory behaviour the present study was undertaken to examine the effects of neonatal dopamine depletion on latent learning. In two experiments dopamine was depleted neonatally, using 6-hydroxydopamine injected intracisternally on day 1 after birth. In both experiments, exploratory behaviour, measured as rearing and head-dip responses in a modified openfield/holeboard, was reduced in the dopamine depleted rats whereas ambulatory behaviour was elevated. In a modified radial arm maze also, rearing responses were decreased while ambulation was increased for the 6-hydroxydopamine treated rats. Latent learning was tested in each experiment following preexposure to the maze for either a single trial or four trials. 6-Hydroxydopamine treated rats demonstrated a comparable latent learning effect to vehicle treated rats after four maze exposures but showed a greatly attenuated latent learning effect following only a single exposure. It is suggested that the effects of neonatal dopamine upon maze and latent learning are secondary to the effects on hyperactivity, reduced exploration and/or increased neophobia shown by these rats.

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