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Biomedical subjects

A M Barnfield

Publications and source records attributed to A M Barnfield.

6 recordsLinked to original sources
PubMed1999

Development of sex differences in spatial memory.

Males typically perform better than females on tests of spatial abilities. However, Silverman and Eals (1992) found that females can surpass males on certain tasks, in particular recall of object location. This study investigated the age at which females begin having greater recall in object location. Recall was tested with object arrays (sets of line drawings of common objects) using samples of 80 adults (M age = 21 yr.) and 139 children at 3 age groups. Adult data replicated earlier findings, indicating significantly greater recall by women. The samples of children at different ages--4 yr. (n = 43), 10-11 yr. (n = 53), and 15-16 yr. (n = 43)--did not show significant sex differences in this type of recall. The findings suggest that females may surpass males in this spatial ability as adults, apparently due to gradual improvements in spatial memory through childhood and adolescence.

Adolescent↗
PubMed1994

d-Fenfluramine and d-norfenfluramine hypophagias do not require increased hypothalamic 5-hydroxytryptamine release.

d-Fenfluramine (2.5 mg/kg i.p.) caused marked hypophagia in food-deprived rats and significantly increased medial hypothalamic extracellular 5-hydroxytryptamine (5-HT) as indicated by in vivo microdialysis. When the drug was given after the 5-HT synthesis inhibitor p-chlorophenylalanine (150 mg/kg per day x 3) the hypophagic response was unimpaired but dialysate 5-HT concentration no longer rose. The d-fenfluramine metabolite d-norfenfluramine (1.5 mg/kg i.p.) caused slightly greater hypophagia than the parent drug and completely blocked feeding in animals pretreated with p-chlorophenylalanine, but dialysate 5-HT was increased in neither circumstance. The results provide evidence against mediation of the hypophagic effects of d-fenfluramine and d-norfenfluramine by increased availability of 5-HT to receptors.

Animals↗
PubMed1989

Flavour aversions conditioned by dl-fenfluramine: a volume independent mechanism.

Fenfluramine, a clinically used anoretic agent, is known to act as a potent unconditioned stimulus in the establishment of a conditioned flavour aversion (CFA). Here we demonstrate that dl-fenfluramine supports the development of a CFA to a novel flavour when drug administration precedes the CS (reverse pairing), although several such UCS/flavour pairings are required under our conditions. In this situation, because fenfluramine exerts a strong anorectic effect, the animals drink little of the flavoured solutions. Artificial reduction of the volume of solutions drunk during conditioning also had no effect on the magnitude of the aversion with either forward or reverse pairings of the UCS and CS. These results suggest an alternative explanation to the idea that a fenfluramine-induced CFA arises as a secondary consequence of delayed stomach emptying.

Animals↗
PubMed1989

A behavioural profile of fluoxetine-induced anorexia.

Fluoxetine is a specific and long-lasting inhibitor of serotonin reuptake. In free-feeding rats a dose of 10 mg/kg reduced meal size but had no significant effect on meal frequency. Feeding rate during meals was also reduced. Direct observation of behaviour associated with eating suggested that fluoxetine did not act by enhancing sleep or other behaviour patterns that interfere with eating, although the transition from feeding to sleep occurred more rapidly after drug treatment. Enhancement of satiety or interference with the sustaining of meals by fluoxetine would be consistent with these data. Rebound feeding after anorexia was not observed in either the meal pattern study or in a separate experiment using schedule fed animals. There was also no clear development of tolerance to the anorectic effect of fluoxetine, and we discuss possible reasons for an association of these two properties.

Animals↗
PubMedDate not supplied

Evidence that mCPP-induced anxiety in the plus-maze is mediated by postsynaptic 5-HT2C receptors but not by sympathomimetic effects.

1-(3-Chlorophenyl)piperazine (mCPP) (0.125-1.0 mg/kg i.p.), previously shown to inhibit social interaction, dose-dependently reduced exploration of the open arms of an elevated plus-maze. These findings suggest anxiogenic properties. The effect of mCPP was more potently inhibited by 1-(1-naphthyl)piperazine than by ketanserin, indicative of its mediation via activation of 5-HT2C rather than 5-HT2A receptors. The 5-HT1B receptor agonist CGS 12066B did not antagonise the anxiety-like response to mCPP, and further reduced exploration at the highest dose tested (10 mg/kg i.p.). Depletion of serotonin (5-HT) by p-chlorophenylalanine (PCPA, 150 mg/kg/day x 3) did not prevent the response, although PCPA itself increased open arm exploration. The 5-HT1A/B and beta-adrenoceptor antagonist 1-propanolol (5 mg/kg i.p.) and the peripheral beta 1-receptor antagonist atenolol (20 mg/kg i.p.) showed no significant activity on the plus-maze either alone or against the anxiogenic effect of mCPP. These results indicate that mCPP induces anxiety in the rat in the elevated plus-maze primarily by stimulation of postsynaptic 5-HT2C receptors, and suggest that sympathomimetic effects of mCPP are not involved.

Adrenergic beta-Antagonists↗