Circling behavior induced by intranigral administration of ruthenium red and 4-aminopyridine in the rat.
We have studied the effects of the unilateral intranigral microinjection of Ruthenium Red and 4-aminopyridine in the rat, as compared with that of muscimol. The three drugs produced contralateral turning when injected into the central nigra reticulata. Muscimol was the most effective but its effect disappeared in 3-4 h, whereas that of Ruthenium Red lasted for up to 3 days. When injected into the caudoventromedial nigra, Ruthenium Red produced intense ipsiversive turning, 4-aminopyridine weak ipsiversive turning and muscimol intense contraversive turning. Pretreatment with haloperidol (i.p.) abolished the effect of Ruthenium Red after injection into the caudoventromedial nigra but only partially reduced it after administration into the central nigra. The effect of muscimol, when injected into either of the nigral regions studied, was only slightly diminished by haloperidol. The release of [3H]GABA in slices of the Ruthenium Red-injected substantia nigra was not altered. Histological examination showed that the microinjected Ruthenium Red was located mainly inside the soma of nigral neurons. It is concluded that alterations of transmitter release are probably responsible for the circling behavior induced by 4-aminopyridine, but the effects of Ruthenium Red seem to be secondary to its penetration into the neuronal somas. Dopaminergic neurons seem to play an important role in the ipsilateral turning induced by Ruthenium Red when injected into the caudoventromedial nigra.
Tapia
R
R
Departamento de Neurociencias, Universidad Nacional Autónoma de México, México, D.F.
Flores-Hernández
J
J
D015761:4-Aminopyridine / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D007839:Functional Laterality; D006220:Haloperidol / Q000494:pharmacology; D008297:Male; D009118:Muscimol / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D012016:Reference Values; D012430:Ruthenium Red / Q000008:administration & dosage / Q000494:pharmacology*; D013238:Stereotaxic Techniques; D013239:Stereotyped Behavior / Q000187:drug effects*; D013378:Substantia Nigra / Q000187:drug effects / Q000502:physiology*; D013997:Time Factors
D012430:Ruthenium Red; D009118:Muscimol; D015761:4-Aminopyridine; D006220:Haloperidol