Increased Burst Firing in Substantia Nigra Pars Reticulata Neurons and Enhanced Response to Selective D2 Agonist in Hemiparkinsonian Rats After Repeated Administration of Apomorphine.
10.3346/jkms.2001.16.5.636
- Author:
Jung Il LEE
1
;
Hee Jung SHIN
;
Do Hyun NAM
;
Jong Soo KIM
;
Seung Chyul HONG
;
Hyung Jin SHIN
;
Kwan PARK
;
Whan EOH
;
Jong Hyun KIM
;
Won Yong LEE
Author Information
1. Department of Neurosurgery, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
- Publication Type:Original Article ; Research Support, Non-U.S. Gov't
- Keywords:
Parkinsonian Disorders;
Quinpirole;
Dyskinesias;
Substantia Nigra
- MeSH:
Animal;
Apomorphine/*pharmacology;
Dopamine Agonists/*pharmacology;
MPTP Poisoning/physiopathology;
Male;
Oxidopamine/toxicity;
Parkinsonian Disorders/*physiopathology;
Quinpirole/pharmacology;
Rats;
Rats, Sprague-Dawley;
Receptors, Dopamine D2/*drug effects;
Substantia Nigra/*drug effects/physiology
- From:Journal of Korean Medical Science
2001;16(5):636-642
- CountryRepublic of Korea
- Language:English
-
Abstract:
Intermittent administrations of dopaminergic agents in hemiparkinsonian rat enhances the behavioral response to subsequent administration of the drugs. This phenomenon is known as "priming" and thought as comparable to drug-induced dyskinesia in patients with Parkinson's disease. We investigated the behavioral and electrophysiological changes in 6-hydroxydopamine (6-OHDA)-lesioned hemiparkinsonian rats after repeated administrations of apomorphine. Administration of apomorphine (0.32 mg/kg, intraperitoneal, i.p.) twice daily for 6 days enhanced the rotation induced by apomorphine from 341 turns/hour at the beginning to 755 turns/hr at the end. At the same time, the response to selective D2 agonist quinpirole (0.26 mg/kg, i.p.) was also enhanced from 203 to 555 turns/hr. Extracellular single unit recording revealed no significant difference in the basal firing rates of substantia nigra pars reticulata (SNr) neurons between the ipsilateral and contralateral side of the 6-OHDA lesion regardless of the repeated administrations of apomorphine. In SNr of the lesion side, the units with burst firing pattern were found more frequently after repeated administrations of apomorphine and the suppressive effect of quinpirole on the firing rate was enhanced. These findings suggest that the increased percentage of the burst units is the important electrophysiological change in the development of enhanced response to selective D2 agonist.
