Shuttlebox Self-Stimulation Behavior Following Intracerebral Microinjections of Morphine Into the Ventral Tegmental-Substantia.

Systemic analgesic injections of morphine have been shown to increase the rate at which rats will lever-press for electrical brain stimulation as well as decrease the current intensity required for this self-stimulation. In the shuttlebox paradigm, the animal crosses from one side of the case to the other in order to turn the current on and off. Similar doses of morphine will selectively increase average ON times per crossing without affecting OFF times. It has been suggested that these effects reflect a sensitization of natural reward pathways by the opioids. Previous work has identified the ventral tegmental-substantia nigral area (VT-SN) area to be quite sensitive to morphine's facilitative effects on intracranial self-stimulation (ICSS). The present study attempted to replicate the reward-enhancing effects of morphine injected into the VT-SN area using the shuttlebox paradigm, a rate-independent measure of reward facilitation. It was found that 5 μg morphine injected into the VT-SN area selectively increased ON times per crossing without affecting OFF times. Systemic naloxone (5 mg/kg) blocked these effects. A dose of 5 μg morphine microinjected into structures surrounding the VT-SN area had no effect on shuttlebox ICSS.

Level thesis:degree_level

Thesis

Year

1982

Author dc:creator

• Horn, Craig Anderson

• Shuttlebox paradigm
• Electrical brain
• Intracranial self-stimulation
• Morphine injected

Repository record dc:identifier

https://digitalcommons.library.uab.edu/etd-collection/7070

OAI identifier oai:identifier

oai:digitalcommons.library.uab.edu:etd-collection-8062