Brain stimulation of the ventral tegmental area attenuates footshock escape: an in vivo autoradiographic analysis of opiate receptors.
An in vivo autoradiographic technique was employed to visualize discrete neuroanatomical changes in opiate receptor binding as a result of aversive footshock (FS) and rewarding electrical brain stimulation (ICS). Footshock-induced escape responding was shown to be attenuated by the simultaneous presentation of non-contingent ICS. Rats were divided into 4 groups (n = 6) receiving ICS, FS, ICS + FS or neither stimulus in an escape paradigm. During the final behavioral test session, rats were injected with 0.002 mg/kg [3H]diprenorphine ( [3H]Dpr) and subsequently prepared for autoradiography. Results indicated two groups of brain areas distinguishable by their treatment-induced changes in [3H]Dpr binding. One group of areas included the nucleus accumbens, claustrum, claustrocortex, perirhinal cortex and ventral tegmental area. These structures showed increased binding due to both FS and ICS. The other group consisted of the diagonal band of Broca, bed nucleus of the stria terminalis, lateral hypothalamus-medial forebrain bundle and amygdala. In these regions, an increase in binding ipsilateral to the electrode was observed in animals receiving ICS with no apparent effect of FS. These results demonstrate that non-contingent ICS may not be strictly aversive and suggest an anatomic, opioid-sensitive basis for both a rewarding and aversive component of this stimulus. It appears, further, that ICS can inhibit the release of endogenous opioid peptides in areas along the mesotelencephalic dopamine pathways, possibly to regulate the activity of neurons conveying reward information. Finally, the observed changes in opiate receptor binding may indicate a mechanism for ICS to produce both drive and reward.
Blake
M J
MJ
Biology Department, Marquette University, Milwaukee, WI 53233.
Stein
E A
EA
D000818:Animals; D001345:Autoradiography; D001921:Brain / Q000033:anatomy & histology / Q000502:physiology*; D004174:Diprenorphine / Q000378:metabolism; D004558:Electric Stimulation; D004597:Electroshock; D004924:Escape Reaction; D008297:Male; D009928:Organ Specificity; D051381:Rats; D011957:Receptors, Opioid / Q000502:physiology*; D012201:Reward; D013681:Tegmentum Mesencephali / Q000502:physiology*; D014316:Tritium
D011957:Receptors, Opioid; D014316:Tritium; D004174:Diprenorphine