The differential contribution of spinopetal projections to increases in vocalization and motor reflex thresholds generated by the microinjection of morphine into the periaqueductal gray.

Cholinergic stimulation of dopamine neurons in the ventral tegmental area (VTA) underlies activation of the brain reward circuitry. Activation of this circuit is proposed to preferentially suppress the affective reaction to noxious stimulation. Vocalization afterdischarges (VADs) are a validated model of the affective response of rats to noxious tailshock. The antinociceptive action of the acetylcholine agonist carbachol microinjected into the VTA on VAD threshold was compared to its effect on the thresholds of other tailshock-elicited responses (VDS = vocalizations during shock, and SMR = spinal motor reflexes). Whereas VADs are organized within the forebrain, VDSs and SMRs are organized at medullary and spinal levels of the neuraxis, respectively. Carbachol (1 μg, 2 μg, and 4 μg) injected into VTA produced dose-dependent increases in VAD and VDS thresholds, although increases in VAD threshold were significantly greater than increases in VDS threshold. Administration of carbachol into VTA failed to elevate SMR threshold. Elevations in vocalization thresholds produced by intra-VTA carbachol were reversed in a dose-dependent manner by local administration of the muscarinic receptor antagonist atropine sulfate (30 μg and 60 μg). These results provide the first demonstration of the involvement of the VTA in muscarinic-induced suppression of pain affect.Perspective-Cholinergic activation of the brain reward circuit produced a preferential suppression of rats' affective reaction to noxious stimulation. The neurobiology that relates reinforcement to suppression of pain affect may provide insights into new treatments for pain and its associated affective disorders.

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Affective Analgesia Following Muscarinic Activation of the Ventral Tegmental Area in Rats

Kender

Harte

Munn

et al. 2008

The Journal of Pain

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Increases in the release and metabolism of serotonin in nucleus parafascicularis thalami following systemically administered morphine in the rat

Munn

Borszcz

2002

Neuroscience Letters

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Захарова

Vasilenko²

2001

Biology Bulletin of the Russian Academy of Sciences

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The differential contribution of spinopetal projections to increases in vocalization and motor reflex thresholds generated by the microinjection of morphine into the periaqueductal gray.

Cited by 7 publications

References 83 publications

Affective Analgesia Following Muscarinic Activation of the Ventral Tegmental Area in Rats

Affective Analgesia Following Muscarinic Activation of the Ventral Tegmental Area in Rats

Increases in the release and metabolism of serotonin in nucleus parafascicularis thalami following systemically administered morphine in the rat

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