Effects of microiontophoretically-applied opioid peptides on Purkinje cells in the cat cerebellum.
OBJECTIVE
The purpose of the present study was to examine the effects of microiontophoretically-applied opioid peptides on Purkinje cell of the cerebellum.


METHODS
The effects of microiontophoretically-applied morphine, leucine-enkephalin (Leu-Enk), methionine-enkephalin (Met-Enk), and dynorphin 1-13 (Dyn) on the spontaneous discharge of Purkinje cells in the cerebellum of the anesthetized cat were examined.


RESULTS
Microiontophoretic applications of Leu-Enk and morphine produced inhibitory and excitatory responses, respectively in Purkinje cells. Application of both morphine and Leu-Enk induced dose-dependent responses. The excitatory responses were antagonized by naloxone, whereas the inhibitory responses were not. Bicuculline, a GABA-A antagonist, completely abolished both the Leu-Enk- and morphine-induced-inhibitory responses. Iontophoretic application of Met-Enk and dyn produced inhibitory responses only. Met-enk- and dyn-induced inhibition was antagonized by naloxone.


CONCLUSIONS
In Purkinje cell activity, microiontophoretically applied Leu-Enk- and morphine-induced excitation is connected with opiate receptors, whereas inhibition is related to the GABA receptor. However, Met-Enk and dyn produced only inhibitory effects via an opiate receptor in the cerebellum of cats.
Taguchi
K
K
Department of Neuroscience, Showa Pharmaceutical University, 3-3165, Higashitamagawagakuen, Machida, Tokyo 194-0042, Japan. taguchi@ac.shoyaku.ac.jp
Abe
K
K
Chyuma
T
T
Kato
M
M
Shigenaga
T
T
Kushida
K
K
Chikuma
T
T
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D002415:Cats; D002531:Cerebellum / Q000502:physiology*; D004399:Dynorphins / Q000494:pharmacology; D004743:Enkephalin, Leucine / Q000494:pharmacology; D004744:Enkephalin, Methionine / Q000494:pharmacology; D005260:Female; D007478:Iontophoresis; D008297:Male; D009020:Morphine / Q000494:pharmacology*; D018847:Opioid Peptides / Q000494:pharmacology*; D010446:Peptide Fragments / Q000494:pharmacology; D011689:Purkinje Cells / Q000502:physiology*
D018847:Opioid Peptides; D010446:Peptide Fragments; D004744:Enkephalin, Methionine; D004743:Enkephalin, Leucine; C026843:dynorphin (1-13); D004399:Dynorphins; D009020:Morphine