Behavioural pharmacology
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Behavioural pharmacology · Oct 2011
Influence of N-methyl D-aspartate receptor mechanism on WIN55,212-2-induced amnesia in rat dorsal hippocampus.
In this study, we investigated the effects of both N-methyl D-aspartate (NMDA) and MK-801 on WIN55,212-2(WIN)-induced amnesia in rats. Step-through inhibitory avoidance of memory was used to examine the retrieval of memory, 24 h after training. All drugs were injected bilaterally into the dorsal hippocampus (intra-CA1) of rats. ⋯ In addition, pretest administration of different doses of the antagonist (2 and 4 µg/rat) induced full recovery of WIN-induced amnesia, but did not influence memory recovery in the subjects, which had received posttraining (0.5 µg/rat) and pretest WIN (0.25 and 0.5 µg/rat). Pretesting coadministration of ineffective doses of WIN (0.1 µg/rat) with NMDA (0.1 µg/rat), but not with MK (1 µg/rat), restored WIN-induced (0.5 µg/rat) amnesia. It can be concluded that the NMDA receptor mechanism located in the dorsal hippocampus may be involved in WIN-induced amnesia.
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Behavioural pharmacology · Oct 2011
Some determinants of morphine effects on intracranial self-stimulation in rats: dose, pretreatment time, repeated treatment, and rate dependence.
Intracranial self-stimulation (ICSS) is a procedure used to evaluate the abuse liability of drugs. The μ opioid receptor agonist morphine is an acknowledged drug of abuse, and this study examined factors that may influence expression of abuse-related morphine effects on ICSS in rats. Adult male rats were equipped with intracranial electrodes targeting the medial forebrain bundle, and 10 stimulus frequencies (56-158 Hz in 0.05 log increments) were available during each daily session under a continuous reinforcement schedule. ⋯ Repeated morphine (3.2-18 mg/kg/day×7 days at each dose) produced tolerance to rate-decreasing effects, enhanced expression of rate-increasing effects, and enhanced rate dependency of morphine effects. Withdrawal from repeated morphine produced small but significant dose-dependent decreases in ICSS. These results show that the magnitude and valence of morphine effects on rates of ICSS in rats are strongly influenced by morphine dose and pretreatment time, history of morphine exposure, and baseline ICSS rate.
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Behavioural pharmacology · Sep 2011
ReviewDelta opioid receptor analgesia: recent contributions from pharmacology and molecular approaches.
Delta opioid receptors represent a promising target for the development of novel analgesics. A number of tools have been developed recently that have significantly improved our knowledge of δ receptor function in pain control. ⋯ These regulatory mechanisms occur at transcriptional and post-translational levels, along agonist-induced receptor activation, signaling and trafficking, or in interaction with other receptors and neuromodulatory systems. All these tools for in-vivo research, and proposed mechanisms at molecular level, have tremendously increased our understanding of δ receptor physiology, and contribute to designing innovative strategies for the treatment of chronic pain and other diseases such as mood disorders.
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Behavioural pharmacology · Sep 2011
The antihyperalgesic effect of cytidine-5'-diphosphate-choline in neuropathic and inflammatory pain models.
This study was designed to test the effects of intracerebroventricularly (i.c.v.) administered CDP-choline (cytidine-5'-diphosphate-choline; citicoline) and its metabolites in rat models of inflammatory and neuropathic pain. The i.c.v. administration of CDP-choline (0.5, 1.0 and 2.0 µmol) produced a dose and time-dependent reversal of mechanical hyperalgesia in both carrageenan-induced inflammatory and chronic constriction injury-induced neuropathic pain models in rats. ⋯ In contrast, i.c.v. pretreatment with the nonselective opioid receptor antagonist naloxone (10 µg) only prevented the CDP-choline-induced antihyperalgesic effect in the neuropathic pain model while the nonselective muscarinic receptor antagonist atropine (10 µg) did not alter the antihyperalgesic effect in the two models. These results indicate that CDP-choline-elicited antihyperalgesic effect in different models of pain occurs through mechanisms that seem to involve an interaction with supraspinal α7-selective nicotinic ACh receptors, and γ-aminobutyric acid B receptors, whereas central opioid receptors have a role only in the neuropathic pain model.
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Behavioural pharmacology · Oct 2010
Intrathecal injection of anti-CX3CR1 neutralizing antibody delayed and attenuated pain facilitation in rat tibial bone cancer pain model.
This study was designed to investigate the effect of intrathecal injection of anti-CX3CR1 neutralizing antibody on pain behaviors in the rat tibial bone cancer pain model. Syngeneic Walker 256 mammary gland carcinoma cells were injected into the tibia medullary cavity to establish the rat model of bone cancer pain. ⋯ Intrathecal injection of anti-CX3CR1 neutralizing antibody both delayed the development of ambulatory pain and hyperalgesia and attenuated established pain facilitation, but had no effects on destruction of bone. Our results suggest that intrathecal injection of anti-CX3CR1 neutralizing antibody delayed and attenuated pain facilitation in the rat tibial bone cancer pain model.