Effect of tryptamine antagonists on self-stimulation. Interaction with amphetamine

Area of Science:

• Neuroscience
• Pharmacology

Background:

• Self-stimulation (SS) behavior is influenced by various neurochemical systems.
• Serotonergic and adrenergic mechanisms are implicated in reward and motivation.

Purpose of the Study:

• To investigate the role of serotonergic mechanisms in self-stimulation (SS) behavior.
• To determine the effects of tryptamine antagonists (cyproheptadine, methysergide) on SS.
• To examine the interaction between serotonergic and adrenergic systems in SS.

Main Methods:

• Rats with brain electrodes in the lateral hypothalamus were used.
• Self-stimulation (SS) behavior was measured via lever-pressing for brain electric stimulation.
• The effects of cyproheptadine and methysergide, alone and in combination with amphetamine, were assessed.

Main Results:

• Both cyproheptadine and methysergide potentiated the enhancing effect of amphetamine on SS.
• Cyproheptadine was significantly more potent than methysergide.
• Cyproheptadine, but not methysergide, increased SS rates when administered alone.

Conclusions:

• Brain serotonergic systems appear to play an inhibitory role in SS.
• Serotonergic mechanisms oppose the facilitatory influence of adrenergic mechanisms on SS behavior.