Article date: 1987/11/1
PubMed ID: 2447909
Journal name: Behavioural brain research (ISSN: 0166-4328)
Injections into the midbrain median raphe nucleus (MR) of the metabolically stable substance P analogue, DiMe-C7, produce dose-dependent increases in locomotor activity (LMA). Ibotenic acid (8.0 micrograms in 2.0 microliter vehicle) lesions of the MR block the hyperkinetic effects of optimal doses of both DiMe-C7 (1.0 microgram in 0.5 microliter vehicle) and the GABAA agonist, muscimol (100 ng in 0.5 microliter vehicle). This observation indicates that the increases in LMA produced by intra-MR DiMe-C7 and muscimol infusion are not due to diffusion to sites outside the MR. Intra-MR administration of the selective serotonin (5-HT) neurotoxin, 5,7-dihydroxytryptamine (6.0 micrograms in 1.5 microliter vehicle), following pretreatment with the norepinephrine and dopamine reuptake inhibitor, nomifensine maleate (15 mg/kg, i.p.), blocked the hyperactivity induced by intra-MR infusions of DiMe-C7 (1.0 microgram) but not that of muscimol (100 ng). These observations suggest that the LMA effects of intra-MR DiMe-C7 and muscimol administration are mediated by different neural mechanisms. The LMA effects of DiMe-C7 depend on intact 5-HT neurons in the MR, whereas the effects of muscimol depend on intact non-5-HT MR cells.
Author List: Paris J M, Lorens S A
Publication Types: Journal Article
Substances mentioned in the article: Peptide Fragments; Ibotenic Acid; Muscimol; 5,7-Dihydroxytryptamine; Serotonin; Substance P; substance P (5-11), pGlu(5)-MePhe(8)-MeGly(9)-; Pyrrolidonecarboxylic Acid;
Mesh terms: 5,7-Dihydroxytryptamine; Animals; Dose-Response Relationship, Drug; Hyperkinesis/chemically induced; Ibotenic Acid; Injections; Male; Muscimol/pharmacology; Neurons/physiology; Peptide Fragments; Pyrrolidonecarboxylic Acid/analogs & derivatives; Raphe Nuclei/cytology; Rats; Rats, Inbred Strains; Serotonin/physiology; Substance P/analogs & derivatives;