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Progress in Neurobiology, 1998
Several pharmacological and neurochemical conditions in rats induce `vacuous' or ... more Several pharmacological and neurochemical conditions in rats induce `vacuous' or `tremulous' jaw movements. Although the clinical significance of these movements has been a subject of some debate, considerable evidence indicates that the non-directed, chewing-like movements induced by cholinomimetics, dopamine antagonists and dopamine depletions have many of the characteristics of parkinsonian tremor. These movements occur within the 3–7Hz peak frequency range
Pharmacology Biochemistry and Behavior, 1999
The role of ventrolateral striatal acetylcholine in the production of tacrine-induced jaw movemen... more The role of ventrolateral striatal acetylcholine in the production of tacrine-induced jaw movements. PHARMACOL BIOCHEM BEHAV 62 (3) [439][440][441][442][443][444][445][446][447] 1999.-The anticholinesterase tacrine induces tremulous jaw movements in rats, and considerable evidence indicates that this response is dependent upon ventrolateral striatal mechanisms. Three experiments were conducted to study the relation between ventrolateral striatal acetylcholine and the production of tremulous jaw movements. In Experiment 1, intracranial microinjection of the acetylcholine synthesis inhibitor hemicholinium-3 into the ventrolateral neostriatum reduced tremulous jaw movements induced by 5.0 mg/kg tacrine. Microinjection of hemicholinium into a cortical site dorsal to striatum (Experiment 2) was without significant effect upon tacrine-induced tremulous jaw movements. In Experiment 3, rats were implanted with dialysis probes in the ventrolateral striatum to measure extracellular levels of acetylcholine during tacrine-induced jaw movements. Tacrine (2.5-5.0 mg/kg) increased both extracellular acetylcholine and tremulous jaw movements. The 5.0 mg/kg dose of tacrine produced a substantial increase in ventrolateral striatal acetylcholine levels (324% of baseline within 30 min). Across all tacrine-treated rats there was a significant linear correlation between tremulous jaw movements and acetylcholine levels ( r ϭ ϩ 0.56) during the first 30-min postinjection period. This correlation was largely due to the group that received 5.0 mg/kg tacrine; within this group, there was a very high correlation ( r ϭ ϩ 0.87) between tremulous jaw movements and acetylcholine levels in the first sample after injection. These data are consistent with the notion that tremulous jaw movements induced by tacrine are mediated by ventrolateral striatal acetylcholine. Moreover, these results suggest that dialysis methods could be used to monitor the relation between striatal acetylcholine and tremulous movements induced by a variety of different conditions.
Neuroscience, 1999
Three experiments were conducted to investigate the behavioral functions of dopamine in the nucle... more Three experiments were conducted to investigate the behavioral functions of dopamine in the nucleus accumbens and ventrolateral striatum. In the first experiment, dialysis probes were implanted in the nucleus accumbens or ventrolateral striatum of rats previously trained to respond on fixed interval lever pressing schedules for food reinforcement. During the dialysis test session, both schedule- and site-dependent effects on dopamine release were observed. Overall, lever pressing on a fixed interval 30-s schedule produced a greater increase in extracellular dopamine than did responding on a fixed interval 120-s schedule. The fixed interval 30-s schedule was also accompanied by a higher rate of lever pressing. Rats with nucleus accumbens probe placements showed significantly higher increases in dopamine release than rats with ventrolateral striatal placements. An additional dialysis experiment showed that baseline levels of dopamine were suppressed by 1.0 microM tetrodotoxin to a similar extent in the nucleus accumbens and ventrolateral striatum. In the third experiment, 6-hydroxydopamine was injected locally into either the nucleus accumbens or the ventrolateral striatum in order to deplete dopamine. Nucleus accumbens dopamine depletions produced only a minor decrease in operant responding, whereas rats with ventrolateral striatal dopamine depletions showed low levels of responding that differed from both the control group and from the group that had accumbens dopamine depletions. Thus, these results are somewhat paradoxical, in that the structure that showed the greatest increase in dopamine release (i.e. the nucleus accumbens) was also the terminal region at which dopamine depletions had very little effect on operant responding. Ventrolateral striatal dopamine appears to be largely permissive over lever pressing, in that normal levels of dopamine in the ventrolateral striatum are critical for responding, although dopamine levels do not fluctuate much during behavioral sessions.
Anesthesia & Analgesia, 1997
... Mediate Antinociception in the Rat Spinal Cord Mohamed Naguib, MB, BCh, MSC, FFARCSI, MD*, an... more ... Mediate Antinociception in the Rat Spinal Cord Mohamed Naguib, MB, BCh, MSC, FFARCSI, MD*, and Tony L. Yaksh, PhDt *Department of Anesthesiology, College of Medicine, King Saud University, Riyadh, Saudi Arabia; and tDepartment of ...
European Journal of Pharmacology - EUR J PHARMACOL, 1999
Four muscarinic receptor antagonists with varying selectivities for the four pharmacologically-de... more Four muscarinic receptor antagonists with varying selectivities for the four pharmacologically-defined muscarinic receptor subtypes (M1–M4) were administered into the lateral ventricle to determine their relative potency in reducing tremulous jaw movements induced by i.p. injection of the muscarinic receptor agonist pilocarpine (4.0 mg/kg). All four muscarinic receptor antagonists reduced tremulous jaw movements in a dose-dependent manner, with the following rank order of potency: scopolamine>methoctramine≥telenzepine>pirenzepine. This pattern is inconsistent with the rank order of affinity of these agents at the muscarinic M1 receptor, and is consistent with their rank order of affinity at muscarinic M2 or M4 receptors. Because tremulous jaw movements are related to striatal function, and the muscarinic M4 receptor is more predominant than the muscarinic M2 receptor as a post-synaptic receptor in striatum, the present results suggest that pilocarpine induces jaw movements due...
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Progress in Neurobiology, 1998
Several pharmacological and neurochemical conditions in rats induce `vacuous' or ... more Several pharmacological and neurochemical conditions in rats induce `vacuous' or `tremulous' jaw movements. Although the clinical significance of these movements has been a subject of some debate, considerable evidence indicates that the non-directed, chewing-like movements induced by cholinomimetics, dopamine antagonists and dopamine depletions have many of the characteristics of parkinsonian tremor. These movements occur within the 3–7Hz peak frequency range
Pharmacology Biochemistry and Behavior, 1999
The role of ventrolateral striatal acetylcholine in the production of tacrine-induced jaw movemen... more The role of ventrolateral striatal acetylcholine in the production of tacrine-induced jaw movements. PHARMACOL BIOCHEM BEHAV 62 (3) [439][440][441][442][443][444][445][446][447] 1999.-The anticholinesterase tacrine induces tremulous jaw movements in rats, and considerable evidence indicates that this response is dependent upon ventrolateral striatal mechanisms. Three experiments were conducted to study the relation between ventrolateral striatal acetylcholine and the production of tremulous jaw movements. In Experiment 1, intracranial microinjection of the acetylcholine synthesis inhibitor hemicholinium-3 into the ventrolateral neostriatum reduced tremulous jaw movements induced by 5.0 mg/kg tacrine. Microinjection of hemicholinium into a cortical site dorsal to striatum (Experiment 2) was without significant effect upon tacrine-induced tremulous jaw movements. In Experiment 3, rats were implanted with dialysis probes in the ventrolateral striatum to measure extracellular levels of acetylcholine during tacrine-induced jaw movements. Tacrine (2.5-5.0 mg/kg) increased both extracellular acetylcholine and tremulous jaw movements. The 5.0 mg/kg dose of tacrine produced a substantial increase in ventrolateral striatal acetylcholine levels (324% of baseline within 30 min). Across all tacrine-treated rats there was a significant linear correlation between tremulous jaw movements and acetylcholine levels ( r ϭ ϩ 0.56) during the first 30-min postinjection period. This correlation was largely due to the group that received 5.0 mg/kg tacrine; within this group, there was a very high correlation ( r ϭ ϩ 0.87) between tremulous jaw movements and acetylcholine levels in the first sample after injection. These data are consistent with the notion that tremulous jaw movements induced by tacrine are mediated by ventrolateral striatal acetylcholine. Moreover, these results suggest that dialysis methods could be used to monitor the relation between striatal acetylcholine and tremulous movements induced by a variety of different conditions.
Neuroscience, 1999
Three experiments were conducted to investigate the behavioral functions of dopamine in the nucle... more Three experiments were conducted to investigate the behavioral functions of dopamine in the nucleus accumbens and ventrolateral striatum. In the first experiment, dialysis probes were implanted in the nucleus accumbens or ventrolateral striatum of rats previously trained to respond on fixed interval lever pressing schedules for food reinforcement. During the dialysis test session, both schedule- and site-dependent effects on dopamine release were observed. Overall, lever pressing on a fixed interval 30-s schedule produced a greater increase in extracellular dopamine than did responding on a fixed interval 120-s schedule. The fixed interval 30-s schedule was also accompanied by a higher rate of lever pressing. Rats with nucleus accumbens probe placements showed significantly higher increases in dopamine release than rats with ventrolateral striatal placements. An additional dialysis experiment showed that baseline levels of dopamine were suppressed by 1.0 microM tetrodotoxin to a similar extent in the nucleus accumbens and ventrolateral striatum. In the third experiment, 6-hydroxydopamine was injected locally into either the nucleus accumbens or the ventrolateral striatum in order to deplete dopamine. Nucleus accumbens dopamine depletions produced only a minor decrease in operant responding, whereas rats with ventrolateral striatal dopamine depletions showed low levels of responding that differed from both the control group and from the group that had accumbens dopamine depletions. Thus, these results are somewhat paradoxical, in that the structure that showed the greatest increase in dopamine release (i.e. the nucleus accumbens) was also the terminal region at which dopamine depletions had very little effect on operant responding. Ventrolateral striatal dopamine appears to be largely permissive over lever pressing, in that normal levels of dopamine in the ventrolateral striatum are critical for responding, although dopamine levels do not fluctuate much during behavioral sessions.
Anesthesia & Analgesia, 1997
... Mediate Antinociception in the Rat Spinal Cord Mohamed Naguib, MB, BCh, MSC, FFARCSI, MD*, an... more ... Mediate Antinociception in the Rat Spinal Cord Mohamed Naguib, MB, BCh, MSC, FFARCSI, MD*, and Tony L. Yaksh, PhDt *Department of Anesthesiology, College of Medicine, King Saud University, Riyadh, Saudi Arabia; and tDepartment of ...
European Journal of Pharmacology - EUR J PHARMACOL, 1999
Four muscarinic receptor antagonists with varying selectivities for the four pharmacologically-de... more Four muscarinic receptor antagonists with varying selectivities for the four pharmacologically-defined muscarinic receptor subtypes (M1–M4) were administered into the lateral ventricle to determine their relative potency in reducing tremulous jaw movements induced by i.p. injection of the muscarinic receptor agonist pilocarpine (4.0 mg/kg). All four muscarinic receptor antagonists reduced tremulous jaw movements in a dose-dependent manner, with the following rank order of potency: scopolamine>methoctramine≥telenzepine>pirenzepine. This pattern is inconsistent with the rank order of affinity of these agents at the muscarinic M1 receptor, and is consistent with their rank order of affinity at muscarinic M2 or M4 receptors. Because tremulous jaw movements are related to striatal function, and the muscarinic M4 receptor is more predominant than the muscarinic M2 receptor as a post-synaptic receptor in striatum, the present results suggest that pilocarpine induces jaw movements due...