The substantia nigra pars reticulata mediates the enhancement of startle by the dopamine D1 receptor agonist SKF 82958 in rats.

Article date: 2004/1/22

PubMed ID: 2147981

Journal name: Psychopharmacology (ISSN: 0033-3158)


These results suggest that activation of D1 receptors in the SNr is necessary for the enhancement of startle by SKF 82958, but that activation of these receptors alone is not sufficient to increase startle. These results also suggest that GABA transmission in the SNr may be involved in the enhancement of startle by SKF 82958. Based on these data, we propose that activation of striatonigral neurons by D1 receptor agonists facilitates GABA release in the SNr to produce the observed enhancement of startle.


Male Sprague-Dawley rats were implanted with cannulae into the SNr and 1 week later infused with either the D1 antagonist SCH 23390 (0.1, 1 microg) or the GABA(A) antagonist bicuculline (0.1 microg), followed by a systemic challenge with the D1 agonist SKF 82958 (1 mg/kg). Other rats were infused with the GABA(A) agonist muscimol (0.1 microg) or SKF 82958 (0.1, 1, 5 microg).


Both SCH 23390 and bicuculline infused into the SNr completely blocked the enhancement of startle by systemic SKF 82958. Muscimol infused into the SNr produced a significant increase in startle by itself, whereas SKF 82958 had no effect.

Author List: Meloni Edward G, Davis Michael

Publication Types: Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, P.H.S.

Substances mentioned in the article: Benzazepines; Dopamine Antagonists; GABA Antagonists; Receptors, Dopamine D1; SK&F 82958; Bicuculline;

Mesh terms: Animals; Benzazepines/pharmacology; Bicuculline/pharmacology; Dopamine Antagonists/pharmacology; GABA Antagonists/pharmacology; Injections, Intraventricular; Male; Motor Activity/drug effects; Rats; Rats, Sprague-Dawley; Receptors, Dopamine D1/agonists; Reflex, Startle/drug effects; Substantia Nigra/drug effects;

Citations: - 9795128

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