Pharmacology, biochemistry, and behavior
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Pharmacol. Biochem. Behav. · Sep 1997
Dietary modulation of mu and kappa opioid receptor-mediated analgesia.
Research has demonstrated that intake of palatable carbohydrates and fats enhanced morphine-induced analgesia (MIA) in Sprague-Dawley rats. To determine if the effects of palatable foods on nociceptive responses would generalize to other strains of animals and other opioid agonists, the present experiments investigated whether intake of palatable foods would: a) alter MIA in Long-Evans rats, and b) alter analgesia produced by drugs acting at kappa opioid receptors. In experiment 1, adult male Long-Evans rats were fed Purina chow alone or chow and either a 32% sucrose solution, a 0.15% saccharin solution, or hydrogenated vegetable fat. ⋯ Experiment 3 compared the analgesic effect of U50,488H (5.0, 10.0, 15.0, and 20.0 mg/kg SC) in rats fed chow alone or chow and either a 0.15% saccharin solution or hydrogenated vegetable fat. Administration of U50,488H led to analgesia. However, %MPEs did not vary directly as a function of dose or as a function of diet. %MPEs of rats fed chow and fat were significantly greater than those of rats fed chow alone after injection of 5.0 mg/kg U50,488H.
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Pharmacol. Biochem. Behav. · May 1997
Nitric oxide synthase inhibition impairs spatial navigation learning and induces conditioned taste aversion.
The free radical gas nitric oxide (NO) is formed from the amino acid precursor L-arginine in brain regions which are associated with learning and the formation of memory. We have previously reported that administration of the nitric oxide synthase (NOS) inhibitor N omega-nitro-L-arginine methyl ester (L-Name) impairs delayed recall in non-human primates but that, at higher doses, impairment is associated with aversive gastrointestinal side effects. The purpose of the present study was to examine the effects of L-Name on learning in a rat spatial navigation task and to assess the ability of L-Name to induce a conditioned taste aversion (CTA) to a novel sucrose solution in a two-bottle choice paradigm. ⋯ These data demonstrate that inhibition of NO activity by L-Name induces significant and selective impairment of cognitive performance at low pharmacologic doses (< 20 mg/kg). However, with higher doses of NOS inhibitors, impairment may be a secondary effect of drug-induced malaise, possibly related to peristaltic dysregulation of gastrointestinal musculature. Therefore, conclusions as to the mediation of learning and memory processes by CNS NO may be difficult to interpret without the use of selective, centrally-acting compounds.
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Pharmacol. Biochem. Behav. · Apr 1997
ReviewA theory of postoperative fatigue: an interaction of biological, psychological, and social processes.
The concept of postoperative fatigue has been developed to explain the feelings of malaise and the reduction in activity during the convalescent period that follows surgery in humans. Fatigue has been assumed to reflect the degree of surgical trauma and to be a consequence of muscle weakness caused by physiological sequelae of the trauma. ⋯ This response, triggered by the patient's perception of the surgical stimulus, is prolonged by the influence of staff and patient expectations, which, in turn, reflect cultural beliefs in the necessity of convalescence. This theory can be tested by manipulation of clinical practice at pharmacological and psychological levels.
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Pharmacol. Biochem. Behav. · Mar 1997
Comparative StudyBeyond sweet taste: saccharin, sucrose, and polycose differ in their effects upon morphine-induced analgesia.
The effects of saccharin, sucrose, or Polycose intake on morphine-induced analgesia (MIA) were examined in 40 adult male Long-Evans rats. Rats were tested for MIA on a tail-flick apparatus following acute (5-h) and chronic (3-wk) intake of a 0.15% saccharin solution, a 32% sucrose solution, a 33.68% Polycose solution, or water. During the chronic phase, all rats were given a choice between the test solution and water. ⋯ Rats drinking Polycose also showed enhanced MIA relative to rats drinking water. Comparison between the acute and chronic phases of the study demonstrated that tolerance to morphine's analgesic effects did not develop in rats drinking Polycose or sucrose, but did develop in rats drinking saccharin or water. The results support the hypothesis that, in addition to palatability, the nutritive value of flavored solutions influences MIA.
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Pharmacol. Biochem. Behav. · Feb 1997
Effects of ddC and AZT on locomotion and acoustic startle. I: Acute effects in female rats.
Several synthetic nucleoside analogues, including AZT(RETROVIR), ddC (HIVID), ddI (VIDEX), and d4T (ZERIT), are currently being used in the treatment of HIV infection. Unfortunately, in clinical use the appearance of severe and sometimes debilitating peripheral neuropathy and pain has been associated with the long-term use of several of these drugs (i.e., ddC, ddI and d4T), although not with AZT. To date, standard pre-clinical animal toxicity studies have failed to reveal any adverse neurologic effects of these compounds. ⋯ Following intragastric administration, ddC reduced locomotion at all but the highest dose, whereas AZT had no significant effect on locomotor activity. Acutely administered ddC had no effect on ASR, whereas AZT increased ASR at the highest stimulus intensity. These data support the use of behavioral testing in the development of the antiviral nucleoside analogues, as behavioral testing may be more effective in identifying the neurologically active agents than is standard toxicity testing.