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The present investigation examined the effects of several dopaminergic compounds in pigeons trained to discriminate either a 0.1 (low) or 5.6 (high) mg/kg dose of the mu opioid butorphanol from saline. Various dopamine (DA) re-uptake inhibitors, releasers, a D1 agonist, a D2 agonist and a D3 agonist engendered partial substitution (50-79% butorphanol(More)
RATIONALE Recent studies indicate that morphine is more potent as an antinociceptive agent in male than female rodents and monkeys. OBJECTIVES To evaluate the influence of sex, nociceptive stimulus intensity and an opioid's relative efficacy on opioid-induced antinociception in rat strains (F344 and Lewis) that display differential sensitivity to morphine(More)
RATIONALE Recent studies indicate that sex and rodent strain are determinants of sensitivity to opioid-induced antinociception. OBJECTIVES The present study examined the influence of sex and rat strain on kappa opioid-induced antinociception using a series of kappa opioids that vary in their relative effectiveness. METHODS In a warm-water (50, 52 and(More)
The present study examined the influence of sex on the antinociceptive effects of (-)-pentazocine, morphine and spiradoline in four rat strains, using a warm-water (50, 52 and 55 degrees C) tail-withdrawal procedure. In F344, Lewis, Sprague-Dawley (SD) and Wistar rats, baseline latencies decreased with increases in water temperature, and at each water(More)
Injection of Complete Freund's adjuvant (CFA) into the hindpaw produces inflammation and alterations in nociceptive sensitivity. The present study was designed to compare the effects of CFA injection into the dorsal and plantar surfaces of the hindpaw on nociceptive sensitivity of the hindpaw to mechanical pressure, warm-water and a hotplate stimulus in(More)
Despite oxycodone's (4,5-epoxy-14-hydroxy-3-methoxy-17-methylmorphinan-6-one) history of clinical use and the attention it has received as a drug of abuse, few reports have documented its pharmacology's relevance to its abuse or its mechanism of action. The purposes of the present study were to further characterize the analgesic effects of oxycodone, its(More)
RATIONALE The purpose of the present investigation was to evaluate the effects of the D3 agonist (+/-)-7-hydroxy-dipropylaminotetralin (7-OH-DPAT), various dopamine (DA) agonists and DA antagonists on the antinociceptive effects of mu opioids. METHODS Antinociception was assessed using a warm-water tail-withdrawal procedure in rats. RESULTS The mu(More)
The present study was designed to examine sex differences in complete Freund's adjuvant (CFA)-induced mechanical hyperalgesia and sex differences in opioid antinociception and anti-hyperalgesia. Female rats developed inflammation and hyperalgesia faster and exhibited greater peak hyperalgesia than male rats. In arthritic (CFA-treated) rats, lower thresholds(More)
RATIONALE The dopamine (DA) D3/2 agonist 7-OH-DPAT attenuates the acute antinociceptive, discriminative stimulus, locomotor activating, and reinforcing effects of mu agonists (for example, morphine). OBJECTIVES To examine the ability of 7-OH-DPAT to modulate the development of morphine tolerance and physical dependence in the rat. METHODS Morphine(More)
RATIONALE Recent studies indicate that mu opioids are generally more potent and effective as antinociceptive agents in male than female rodents. OBJECTIVES To evaluate the influence of sex on the development of tolerance to the antinociceptive effects of morphine and cross-tolerance to the lower efficacy mu opioids buprenorphine and dezocine in F344 and(More)