The Actions of Cocaine in the Brain

The Actions of Cocaine in the Brain

Cocaine’s mode of action has been shown to involve the dopamine receptors. This paper will discuss how cocaine affects dopamine receptors, the mode of addiction, how cocaine affects the frontal brain metabolic activities, as well as the role of excitatory amino acids in cocaine’s mechanism. I will also discuss how cocaine affects another system through its mechanism on the brain—the renin angiotensin system.

Cocaine influences dopamine, norepinephrine and serotonin neurotransmission by inhibiting their reuptake. Pimozide, alpha-flupenthixol, perphenazine and chlorpromazine, all dopamine antagonists, were used to pre-treat rats in an attempt to demonstrate the reinforcing effects of dopamine. Because rats demonstrated a reduced rate of self-administration during extinction as well as after pre-treatment with antagonists, it is conceivable that dopamine receptors are involved in the reinforcing effects of cocaine (Hubner & Moreton, 1991).

Two dopamine receptors, B1 and B2, are believed to be involved in these rewarding effects of cocaine. Rats were trained to self-administer cocaine intravenously on a fixed-ratio (FR) 5 schedule of reinforcement. When these rats were pretreated with SCH23390, a D1 antagonist, and spiperone, a D2 antagonist, their response rates varied. At doses up to l0ug/kg, the rats exhibited an increased response rate; whereas at doses higher than this, the rats showed a decrease in their response rate. A similar decrease in response rate was produced when central dopamine containing neurons were destroyed with the neurotoxin, 6-hydroxy-dopamine (Hubner &Moreton, 1991).

The mode of action of the D1 receptor subtype is on adenylate cyclase. Upon activation, it s...

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