Potentiation of yawning responses to the dopamine receptor agonists B-HT 920 and SND 919 by pindolol in the rat

The present study was undertaken to determine the state of sensitivity of dopamine D2/D3 receptors involved in the mediation of yawning behaviour at various times following acute morphine administration to rats. Morphine (3.0 mg/kg, s.c.) induced a biphasic effect on locomotor activity: an initial inhibitory phase lasting for about 30 min was after about an hour followed by a phase of locomotor activation lasting for about 60 min. Dopamine D2/D3 receptor agonist quinpirole (0.01-0.1 mg/kg, s.c.) induced yawning behaviour in rats. Morphine given at 15 or 60 min before (inhibitory phase) inhibited the yawning response to quinpirole (0.1 mg/kg) but not when given at 90 or 120 min before (stimulatory phase). Naloxone (1.0 mg/kg) given 10 min before quinpirole restored yawning inhibited by morphine pretreatment during the inhibitory phase (15-60 min after morphine). However, during the morphine-induced stimulatory phase naloxone strongly inhibited the yawning response to quinpirole. D1 receptor antagonist SCH 23390 [R-(+)-8-chloro-2,3,4,5-tetrahydro-3-methyl-5-phenyl-1H-3- benzazepin-7-ol hemimaleate] at 0.01 mg/kg did not affect quinpirole-induced yawning or its inhibition by morphine. However, in rats which received morphine 90 min prior to testing yawning, SCH 23390 enhanced quinpirole-induced yawning behaviour as compared with morphine- or saline-pretreated animals. The data obtained in the present study indicate that morphine pretreatment initially induces a lack of responsiveness of the D2/D3 receptors mediating yawning behaviour and subsequently increases their sensitivity.(ABSTRACT TRUNCATED AT 250 WORDS)

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Role of dopamine receptors in the dual effect of naloxone on quinpirole-induced yawning in morphine pretreated rats

Zharkovsky

Moisio

Kivastik

et al. 1993

Naunyn-Schmiedeberg's Arch Pharmacol

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Possible involvement of differing classes of dopamine D-2 receptors in yawning and stereotypy in rats

et al. 1990

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The present experiments were performed to investigate differences in the properties of the dopamine D-2 receptors related to yawning and stereotypy. Subcutaneous injection of talipexole (B-HT 920) (10-250 micrograms/kg) or SND 919 ((S)-2-amino-4,5,6,7-tetrahydro-6-propylamino-benzothiazole) (25-500 micrograms/kg) evoked yawning behavior with bell-shaped responses. However, SK&F 38393 (1-phenyl-2,3,4,5-tetrahydro-(1H)-3-benzazepine-7,8-diol) (0.5-10 mg/kg SC) did not elicit yawning and decreased yawning responses to low doses of talipexole (25 micrograms/kg SC) or SND 919 (100 micrograms/kg SC). These low but effective doses for inducing yawning of talipexole or SND 919 in combination with SK&F 38393 (0.5-10 mg/kg SC) did not elicit stereotypy. In contrast, yawning behavior was not produced after very high doses of talipexole (500 micrograms/kg SC) or SND 919 (1000 micrograms/kg SC) given alone or in combination with SK&F 38393 (0.5-10 mg/kg SC). These extremely high doses of talipexole or SND 919 evoked slight stereotypy, which was enhanced by the combined treatment with SK&F 38393. The present results suggest that the dopamine D-2 receptors related to yawning are more sensitive to dopamine receptor agonists than those related to stereotypy, and that concurrent stimulation of postsynaptic dopamine D-1 receptors with D-2 receptors reduces the incidence of yawning but enhances that of stereotypy.

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Action of intravenously administered talipexole on the rat striatal neurons receiving excitatory input from nigral dopamine neurons

Matsubayashi

Amano

et al. 1995

Psychopharmacology

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Electrophysiological studies using rats anesthetized with chloral hydrate were performed to elucidate whether or not intravenously injected talipexole acted as a D2 receptor agonist on the striatal neurons in comparison with the action of bromocriptine. The activities of the striatal neurons were extracellularly recorded using a glass microelectrode attached along a seven-barreled micropipette, each barrel of which was filled with talipexole, bromocriptine, SCH23390 (D1 antagonist), domperidone (D2 antagonist), glutamate or 2 M NaCl. These drugs were iontophoretically applied to the immediate vicinity of the target neuron being recorded. The effects of talipexole and bromocriptine were examined on the neurons, whose spikes (induced by the stimulation of the substantia nigra pars compacta) were inhibited by the iontophoretic application of domperidone. Iontophoretic application of talipexole or bromocriptine increased spontaneous firing of these neurons and this increase in firing was also inhibited by iontophoretically applied domperidone. In the same neurons, intravenously administered talipexole (0.01, 0.02 and 0.04 mg/kg) dose-dependently increased firing, and this increase was inhibited by microiontophoretically applied domperidone, but not by SCH23390. On the other hand, the intravenous injection of bromocriptine (0.1, 0.2 and 0.4 mg/kg) also increased the firing rate. However, the increase was not dose-dependent and fluctuated; the firing transiently decreased during the increase in firing with intravenously administered bromocriptine. However, the bromocriptine-induced increase in firing was also suppressed by domperidone, and decrease in firing was inhibited by SCH23390. These findings suggest that talipexole acts as a D2 agonist on the striatal neurons receiving input from substantia nigra pars compacta and increases firing when intravenously applied.(ABSTRACT TRUNCATED AT 250 WORDS)

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Potentiation of yawning responses to the dopamine receptor agonists B-HT 920 and SND 919 by pindolol in the rat

Cited by 14 publications

References 21 publications

Role of dopamine receptors in the dual effect of naloxone on quinpirole-induced yawning in morphine pretreated rats

Role of dopamine receptors in the dual effect of naloxone on quinpirole-induced yawning in morphine pretreated rats

Possible involvement of differing classes of dopamine D-2 receptors in yawning and stereotypy in rats

Action of intravenously administered talipexole on the rat striatal neurons receiving excitatory input from nigral dopamine neurons

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