title: Anatomic and pharmacologic differences between two types of aversive midbrain stimulation.
abstract: Chronic stimulating electrodes were implanted into two separate midbrain sites in rats. One site was the dorsal central gray area (DCG), where electrical stimulation produced frantic, escape-seeking behavior which grossly appeared fear-like and/or pain-like. The other site was in the ventral reticular formation (VRF), where stimulation produced a stereotyped circling response. Stimulation at both sites was aversive in that these animals would bar press for escape in a decremental bar-pressing paradigm. In this paradigm, each bar press decremented the current by five per cent of the initial current level. Following the acquisition of stable baseline decremental bar-pressing performance, animals were given injections of either the serotonin-depleting drug, para-chlorophenylalanine (PCPA), or the catecholamine-depleting drug, alpha-methyl-para-tyrosine (AMPT). Control animals received normal saline. Compared to saline control animals, PCPA-injected DCG-stimulated animals showed a marked increase in decremental bar pressing, whereas VRF-stimulated animals showed no change. AMPT-injected VRF-stimulated animals showed a marked decrease in decremental bar pressing, but the DCG-stimulated animals were not affected. These results suggest that escape behavior from electrical stimulation of midbrain sites is mediated by more than one neural system.
mesh_terms: D000818:Animals; D001931:Brain Mapping; D003216:Conditioning, Operant / Q000187:drug effects / Q000502:physiology; D004558:Electric Stimulation; D004924:Escape Reaction / Q000187:drug effects / Q000502:physiology*; D005239:Fear / Q000187:drug effects / Q000502:physiology; D010134:Fenclonine / Q000494:pharmacology*; D006801:Humans; D008297:Male; D008636:Mesencephalon / Q000502:physiology*; D008781:Methyltyrosines / Q000494:pharmacology*; D009619:Nociceptors / Q000502:physiology; D051381:Rats; D012154:Reticular Formation / Q000502:physiology; D012701:Serotonin / Q000378:metabolism; D013239:Stereotyped Behavior / Q000187:drug effects / Q000502:physiology
chemical_list: D008781:Methyltyrosines; D012701:Serotonin; D010134:Fenclonine