Abstract
In a series of experiments it was demonstrated that defecation responses induced in rats by exposure to novel environments did not habituate if the animals were treated with alpha-melanocyte stimulating hormone (alpha-MSH). The MSH-treated rats sustained high defecation responses on 6 successive days of exposure, whereas control rats habituated. The role of plasma 11-hydroxycorticosterone (11-OHCS) levels and brain catecholamines (CAs) in this novelty-induced defecation following alpha-MSH administration was also investigated. Baseline studies showed that MSH treatment alone increased plasma 11-OHCS levels in the resting condition and lowered brain dopamine (DA) but not norepinephrine (NE) concentrations. It was found, however, that plasma 11-OHCS levels in MSH-treated rats were not significantly increased on successive days of combined MSH and novelty treatments but that whole brain DA and NE concentrations were both lowered. A strong negative correlation was observed between defecation responses and brain DA concentrations on successive days of the joint MSH and novelty treatment. In all the experiments alpha-MSH treatment had no effect on step-down activity.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callMore From: Journal of comparative and physiological psychology
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
