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Abstract: Cannabinoid CB1 receptor antagonists can decrease methamphetamine self-administration. This study examined whether the CB1 receptor antagonist AM251 [N-(piperidin-1-yl)-5-(4-indophonyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide] modifies reinstatement in rats that previously self-administered methamphetamine. Rats (n =10) self-administered methamphetamine (0.1 mg/kg/infusion) under a fixed ratio 2 schedule. Non-contingent methamphetamine (0.01–1.78 mg/kg, i.v.) yielded responding for saline (reinstatement) that was similar to responding for self-administered methamphetamine. AM251 (0.032–0.32, i.v.) did not affect methamphetamine-induced reinstatement but significantly attenuated ▵9-tetrahydrocannabinol (2.0 mg/kg, i.p.)-induced hypothermia. These data fail to support a role for endogenous cannabinoids or cannabinoid CB1 receptors in reinstatement and, therefore, relapse to stimulant abuse. [Copyright &y& Elsevier]

The effects on one-way active avoidance conditioning of pre-training, systemic administration of the selective μ-receptor agonist [ d-Ala,N-Me-Phe, Glyol]enkephalin (DAGO), and the selective μ-receptor antagonist ( d-Phe-Cys-Tyr- d-Trp-Orn-Thr-Pen-Thr-NH (CTOP), were determined in Swiss-Webster mice. A low dose of DAGO (0.92 µg/kg) moderately enhanced avoidance acquisition, whereas a 100 µg/kg dose of CTOP more dramatically impaired acquisition. However, the avoidance-enhancing dose of DAGO significantly increased locomotor activity as measured in a separate group of mice in the avoidance chamber, and the avoidance-impairing dose of CTOP significantly decreased activity. Under these same training conditions, earlier studies (Schulteis et al. 1988; Schulteis and Martinez 1990) demonstrated that enkephalins impaired avoidance learning, and selective δ-receptor antagonists such as ICI 174,864 enhanced learning; in contrast to the present study, both of these effects were dissociated from performance effects such as alterations in locomotor activity. Taken together, the results suggested that the effects of enkephalins were mediated by the δ-, but not μ-, class of opioid receptor. [ABSTRACT FROM AUTHOR]

Osgood's Semantic Differential Technique was used to investigate responses of Chicano and Anglo high school students on five concepts viewed as basic to the traditional Mexican family structure: (1) self, (2) male, (3) female, (4) father, and (5) mother. It was found that the Chicanos and Anglos differed significantly on the five concepts, suggesting that these concepts have different affective meanings for the two cultural groups. The results also showed that the differences seem to be centered around the Potency dimension. In addition, there were sex differences, also centered around the Potency dimension, as well as an ethnic by sex interaction. [ABSTRACT FROM PUBLISHER]

Methylnaloxonium, a quaternary form of naloxone that does not readily cross the blood brain barrier, enhanced acquisition of a Y-maze shock escape and a one-way active avoidance response in mice in doses that did not affect shock-induced locomotor activity in an open field. Since methylnaloxonium is a opioid antagonist, it is likely that the observed enhancement of learning is due to the drug preventing endogenous opioid peptides from reaching their receptors. The results therefore suggest that manipulation of peripheral opioid systems alters the strength of a conditioned response. [ABSTRACT FROM AUTHOR]

Bilateral subseizure stimulation of the amygdala given immediately following training in an inhibitory avoidance task produced retrograde amnesia. Hexamethonium (3.0 and 10.0 mg/kg), a peripherally acting nicotinic cholinergic antagonist, attenuated the retention deficits induced by amygdala stimulation if the drug was given 30 min prior to, but not immediately following training. Hexamethonium had no effect in normal unoperated animals, but did produce a retention defecit in operated control (nonstimulated) animals if it was given immediately following training (3.0 and 10.0 mg/kg). The results suggest that memory deficits induced by electrical stimulation of the amygdala are associated with, or perhaps mediated in some way by peripheral autonomic function. [ABSTRACT FROM AUTHOR]

Graded doses of sodium nitrite were administered shortly before or immediately after a single training trial in an inhibitory avoidance task. A retention test was given at 24 h (rats) or 72 h (mice) after training. The results indicate that sodium nitrite impairs acquisition of an inhibitory avoidance response in rats and mice. Retention was impaired with doses lower than those required for producing hypoxic effects, as measured by the EEG, methemoglobin levels in the blood, blood pressure, and heart rate. Since hypoxia was not involved, it is likely that the effects were mediated by some direct action of sodium nitrite on the CNS. [ABSTRACT FROM AUTHOR]

Norepinephrine levels of old and young F344 rats of both sexes were compared in several organs that receive sympathetic innervation. In addition, both norepinephrine and epinephrine concentrations in the adrenal medulla of young and old rats were determined. A rationale was developed for making age-related comparisons of the catecholamine content in peripheral organs which accounted for age-related changes in organ weight and body weight. It was found that norepinephrine concentrations were decreased for old male rats in heart auricles. In contrast, in old female rats there were no age-related changes in the catecholamine content of any peripheral organ. [ABSTRACT FROM PUBLISHER]

This experiment examined the effect of post-training d-amphetamine on retention in an appetitive autoshaping conditioning situation. Harlan Sprague-Dawley rats were first given ten autoshaping trials, followed by either three or four additional sessions of 50 trials (70 s intertrial interval) on which the conditioned stimulus (the extension of an illuminated Plexiglas lever for 10 s) and unconditioned stimulus (a 45 mg food pellet), were paired. d-Amphetamine (1 or 2 mg/kg) or saline was administered IP either immediately or 2 h following training. Rats injected with 1 mg/kg d-amphetamine immediately after the first training session made significantly more responses during the conditioned stimulus presentation on the following daily session of 50 trials. Thus, the amphetamine-treated rats acquired the lever press response faster than those given only saline. The amphetamine effects were time dependent: no significant effects were found if the injection was delayed until 2 h following training. These results agree with the findings of other instrumental aversive facilitation studies and suggest that d-amphetamine may enhance retention of the classically conditioned components of autoshaping. [ABSTRACT FROM AUTHOR]