Drug addiction refers to the continued use of mood altering substances despite adverse consequences. The need for pleasure is what drives people to addiction. Studies on animals like rats help to understand effects of drugs in human beings. Gilpin, Richardson, and Koob studied the selective breeding of rats over generations and alcohol dependence. The researchers hypothesized that dependence-induced increase in consumption of alcohol by rats was sensitive to naltrexone. They also hypothesized that dependence induced increases in the consumption of alcohol by rats were sensitive to CRF1-receptor antagonist MPZP. Roberto et al. conducted a study on Corticotropin-releasing factor (CRF) and gamma-aminobutyric acid (GABA)ergic system in the central amygdala (CeA) and their implication on to alcohol induced behavior. The study hypothesis was that CRF and GABAergic systems in the CeA were implicated in the high-anxiety and high-drinking profile that was associated with ethanol dependence. Another hypothesis was that Ethanol augmented the release of CA GABA in ethanol-naive rats and mice. Walker, Zorrila and Koob researched on the effects of systematic k-Opioid receptor antagonism by nor-binaltorphimine on dependence induced excessive alcohol use in rats. Their hypothesis was that peripherally-administered nor-binaltorphimine could reduce dependence-induced self administration of ethanol. All the three studies attempted to explore affects alcohol on rats.
Gilpin, Richardson, and Koob trained 20 rats to respond for water and alcohol in a two lever operant condition during daily sessions that lasted 30 minutes. The researchers then matched the rats for alcohol intake and exposed them to chronic intermittent alcohol vapor or ambient air for about ten weeks. The rats were later given MPZP and naltrexone in two "separate and consecutive Latin-square designs". MPZP refers to a small molecule CRF- receptor antagonist. Naltrexone refers to a general opioid receptor antagonist. The results were that MPZP abated dependence-induced increases in the intake of alcohol by the rats. In addition, MPZP had no effect on the consumption of alcohol by non-dependent controls. Naltrexone reduced, in similar proportions, the operant alcohol response in dependent and non dependent rats. The study led to the conclusion that brain CRF1-receptor systems were crucial in the regulation of dependence-induced consumption of alcohol, and that brain opioid systems were crucial in regulating basal alcohol consumption by rats.
Roberto et al. used naive and ethanol-dependent rats to compare electrophysiologic effects and interactions of corticotropin-releasing factor (CRF) and ethanol on CeA GABAergic transmission. The researchers measured GABA dialyzate in CeA for CRF and CRF1 through the use of real-time polymerase chain reaction. They assessed effects of chronic treatment with CRF1 antagonist on withdrawal-induced increases in alcohol consumption in dependent rats. The results were that CRF and gamma-aminobutyric acid systems in the central amygdala (CeA) were crucial in the high-anxiety and high-drinking profile that was associated with ethanol dependence. The findings indicated a key role for presynaptic CRF GABA interactions in CeA in the maintenance and development of the dependence on ethanol.
Walker, Zorrila and Koob housed and trained adult male rats to self-administer 10% alcohol. After the rats stabilized the self-administration, they were split into two groups. One group became the ethanol exposure group while the other the air exposed control group. After observation, the results were that altered dynorphin opioid peptide systems contributed to increased ethanol self-administration. The implication of the study was "the K-opioid/dynorphin system is a viable pharmacotherapeutic target for the treatment of alcoholism" (Walker, Zorrila and Koob 118).
Overall, the above studies indicate that continued drug use leads to addiction. Besides, the studies show that there may be treatment for alcoholism. This is because the observed effect in rats may also be applicable to human beings. Further research is crucial to reveal the applicability of the results to human beings.