Biomedical subjects

Jonathon D Crystal

Publications and source records attributed to Jonathon D Crystal.

5 recordsLinked to original sources

PubMed2003

Cannabinoid modulation of sensitivity to time.

The present studies used a psychophysical approach to examine the effect of cannabinoids on temporal processing. Rats trained to discriminate 2- and 8-s (Experiment 1, n=72) and 4- and 16-s (Experiment 2, n=60) intervals were tested with intermediate durations. Psychophysical functions for time, relating the probability of judging a duration as "long" as a function of the actual stimulus durations, were characterized by measures of central tendency (point of subjective equality, PSE) and variability (Weber fraction, WF). The potent cannabinoid agonist, WIN55,212-2 (1-3 mg/kg), produced a dose-related decrease in sensitivity to time (i.e. increase in WF) without systematically affecting PSE (Experiments 1 and 2). The central cannabinoid CB1 antagonist, SR141716A (1-3 mg/kg), did not alter either the WF or PSE (Experiments 1 and 2). Coadministration of SR141716A with WIN55,212-2 blocked the effect of the agonist on WF (Experiment 2), suggesting that the WF effect is mediated by actions at cannabinoid CB1 receptors. Computational modeling with an information processing theory of timing suggests that the reduction in sensitivity to time can be attributed to a disorder of attention.

Analgesics↗

PubMed2002

Intravenous self-administration of amphetamine is increased in a rat model of depression.

Affective disorders and substance abuse frequently coexist, yet few previous studies have examined drug self-administration using animal models of depression. The olfactory-bulbectomized rat is a well-established model that exhibits a high degree of neurochemical similarity to depression. Olfactory bulbectomy (OBX) increases dopamine receptor densities in the ventral striatum, which may increase the reinforcing effects of drugs of abuse. Experiments were designed to test the hypotheses that acquisition and stable self-administration of amphetamine would be increased in bulbectomized rats. In the first experiment, rats underwent bilateral OBX or sham surgery and intravenous jugular catheters were implanted 12-14 days later. Acquisition was examined using a standard operant paradigm involving a nose-poke response for a very low dose of D-amphetamine sulfate (12 microg/infusion, IV). A separate group of rats received coinfusions of sulpiride. In a second experiment designed to minimize differences in acquisition and examine stable self-administration, lever pressing for a low (0.10 mg/kg, IV) or high (0.25 mg/kg, IV) dose of D-amphetamine sulfate was measured in rats pretrained to lever press for food. Bulbectomized rats acquired the self-administration of very low dose amphetamine faster than sham-operated rats and this effect was reversed by sulpiride coinfusion. Stable self-administration of the low dose of amphetamine was also markedly increased in bulbectomized rats. The findings reveal the utility of the OBX model for studying the neurobiological basis of depression and drug abuse comorbidity and support the hypothesis that neurochemical abnormalities associated with depression may enhance the addictive properties of some drugs of abuse.

Amphetamine↗

PubMed2002

Simultaneous temporal and spatial processing.

Rats searched for food that was contingent on time and place in an open field. One location was active at a time, the active location moved in a clockwise direction after each reward, and each location was repeated several times on each daily session. When a location was active, the first response after a fixed interval produced food. The intervals associated with each of the four locations were consistently 60, 30, 30 and 60 sec. For independent groups, inspecting an inactive location had no consequence (n = 7) or reduced the amount of food delivered at the active location (n = 6). The rates of inspecting active and inactive locations increased before the associated intervals elapsed, with preferential responding at the active locations. Rates of anticipation at active locations failed to superimpose when plotted as a function of proportional time. Simultaneous temporal and spatial processing contributed to the failure of proportional timing.

Animals↗

PubMed2002

Representation of time in time-place learning.

Ordinal, interval, and circadian mechanisms of solving a time-place task were tested. Rats searched for food twice in the morning and once in the afternoon (Group AB-C, n = 5) or once in the morning and twice in the afternoon (Group A-BC, n = 5) in a box with four food troughs. The location of the food depended on the time of day in a 12:12-h light:dark cycle. Acquisition was documented by food-site inspections at the correct locations prior to food availability. On nonrewarded probes, the time of the middle search (B) was shifted late (for Group AB-C) or early (for Group A-BC). The rats visited Location B at chance, contrary to an ordinal mechanism. When the posttesting meal and light-dark transitions were omitted, the rats visited correct locations with impaired performance but at above-chance levels on nonrewarded probes. The results are consistent with interval and circadian representations of time.

Animals↗

PubMed2002

Data archiving for animal cognition research: report of an NIMH workshop.

In July 2001, the National Institute of Mental Health sponsored a workshop titled "Data Archiving for Animal Cognition Research." Participants included scientists as well as experts in archiving, publishing, policy, and law. As is described in this report, the workshop resulted in a set of conclusions and recommendations concerning (A) the impact of data archiving on research, (B) how to incorporate data archiving into research practice, (C) contents of data archives, (D) technical and archival standards, and (E) organizational, financing, and policy issues. The animal cognition research community is encouraged to begin now to establish archives, deposit data and related materials, and make use of archived materials in new scientific projects.

Animals↗