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At least 145 records · Page 8Linked to original sources
PubMed1991

The competitive NMDA antagonist AP5, but not the non-competitive antagonist MK801, induces a delay-related impairment in spatial working memory in rats.

Rats were trained to alternate responses on a discrete trial working memory task on a T-maze. In Experiment 1, the rats were then matched for choice accuracy and allocated to three treatment groups. These were: implantation of osmotic minipumps for intraventricular infusion of either (a) 15 mM D-2-amino-5-phosphonopentanoic acid (AP5) or (b) artificial cerebrospinal fluid (VEH); and an unoperated control group (UNOP). In Phase 1 we assessed alternation performance with a minimal delay between responses: the UNOP and VEH rats continued to choose accurately; the AP5 rats showed an impairment of choice accuracy, but recovered over days. In Phase 2 a 20-s delay between responses was enforced, and choice accuracy was assessed following injections either of saline or of Milacemide HCl (10 mg/kg). There was now a severe and enduring impairment of choice accuracy in the AP5 group, but Milacemide injections did not affect performance in any of the treatment groups. In Experiment 2 rats were trained in a similar way, and then given intraperitoneal injections of MK801 or of physiological saline in a within-subjects design and tested for T-maze performance with a minimal or a 20-s delay between responses. In the first Phase, MK801 was given 10-min before behavioural testing commenced; in the second Phase, it was given 28-40 min before behavioural testing commenced. The outcome depended critically on the time between drug injection and testing. There was a significant drug-induced impairment of choice accuracy in both Phases; but in Phase 1 there was no impairment in testing with a minimal retention interval and an impairment with a 20-s retention both retention intervals. We conclude that AP5, but not MK801, interferes with temporary memory storage in a delay-dependent manner.

2-Amino-5-phosphonovalerate↗
PubMed1985

Effects of valproate on hyponeophagia in rats: competitive antagonism with picrotoxin and non-competitive antagonism with RO 15-1788.

The effects of valproate (30-500 mg/kg), alone and in combination with picrotoxin (1.5 mg/kg) or RO 15-1788 (10 mg/kg) were studied in two experiments on hyponeophagia in rats. Valproate reduced eating latency and increased eating time and amount eaten of novel food, except at 500 mg/kg which reduced feeding. Picrotoxin induced generally opposite actions alone and shifted valproate dose/response curves to the right. RO 15-1788 had no detectable intrinsic action, but prevented both the behavioural facilitation and inhibition produced by valproate. These findings are discussed in the context of the GABA hypothesis of benzodiazepine action, with the conclusions that they provide behavioural support for the hypothesis of a receptor complex with GABA and benzodiazepine binding sites, and that an optimal and submaximal level of activity at the benzodiazepine site is a necessary condition for anxiolytic actions of valproate.

Animals↗
PubMed1990

Plasma beta-endorphin and beta-lipotropin levels increase in well trained athletes after competition and non competitive exercise.

Plasma beta-endorphin (beta-EP) and beta-lipotropin (beta-LPH) levels were measured in 15 healthy trained marathon runners. These hormones were evaluated in two different conditions: 1-before (1h) and after a marathon race (n = 10); 2-before, during and after a prolonged (90 min) submaximal exercise (bicycle ergometer at 50% VO2 max) (n = 5). In these latter group plasma beta-EP and beta-LPH levels were measured every 15 min for 165 min. In all the athletes, both plasma beta-EP and beta-LPH levels were significantly higher after the end of the marathon race than in basal conditions (p less than 0.01). The prolonged exercise with bicycle ergometer significantly stimulated plasma beta-EP and beta-LPH levels. Starting 60 min after the beginning of the exercise, plasma beta-EP and beta-LPH levels resulted significantly higher than basal values until the end of the exercise (p less than 0.01 at 60, 75 and 90 min). These data confirming that marathon running is a potent stress stimulus, showed that the duration and related factors but not the work load may be considered critical in stimulating beta-EP and beta-LPH release during physical exercise.

Adult↗
PubMed1992

Competitive inhibition of lipolytic enzymes. V. A monolayer study using enantiomeric acylamino analogues of phospholipids as potent competitive inhibitors of porcine pancreatic phospholipase A2.

For the first time, we have shown that a stereospecific interaction occurs between porcine pancreatic phospholipase A2 and a monomolecular film of amidophospholipid used as inhibitor. Direct binding experiments, using radiolabelled phospholipase A2, showed that 13 times more enzyme was bound to phospholipid films of the L series by comparison with films of the D series. These results were confirmed by indirect binding studies using re-spreading experiments. Kinetic studies of the porcine pancreatic PLA2, using enantiomeric acyl-amino phospholipid analogues, have shown that: (1) inhibitors of the L series are more potent than inhibitors of the D series, (2) inhibitors having a negative charge are more potent than zwitterionic inhibitors, (3) inhibitory power values are greater when evaluated in micellar system than in a the monolayer system, (4) the inhibitory power increases continuously with surface pressure.

Animals↗