Behavioral actions of baclofen in the rat ventromedial thalamic nucleus: antagonism by delta-aminovalerate.
Baclofen, an agonist at GABAB receptors injected locally into the rat ventromedial thalamic nucleus (VM) induced catalepsy in a dose-dependent, stereospecific and site-specific way. Baclofen-induced catalepsy was accompanied by tonic activity in the electromyogram (EMG) recorded from the gastrocnemius muscle, which is considered to be a measure of limb rigidity. delta-Aminovalerate (delta-AVA) coadministered with baclofen into the VM prevented the development of both catalepsy and limb rigidity. delta-AVA injected alone into the VM was devoid of depressant or stimulating behavioral effects. In contrast to delta-AVA, bicuculline, a GABAA antagonist, failed to antagonize baclofen-induced catalepsy. On the other hand, catalepsy due to local injection of a GABAA agonist, muscimol into the VM was antagonized by bicuculline, but not by delta-AVA. The present results suggest that delta-AVA may be useful as an antagonist of central pharmacological actions of baclofen.
Wüllner
U
U
Max-Planck-Institute for Experimental Medicine, Göttingen, F.R.G.
Klockgether
T
T
Schwarz
M
M
Sontag
K H
KH
D000596:Amino Acids / Q000008:administration & dosage* / Q000494:pharmacology; D021542:Amino Acids, Neutral; D000818:Animals; D001418:Baclofen / Q000008:administration & dosage* / Q000037:antagonists & inhibitors / Q000494:pharmacology; D001640:Bicuculline / Q000494:pharmacology; D002375:Catalepsy / Q000139:chemically induced* / Q000503:physiopathology; D004305:Dose-Response Relationship, Drug; D004338:Drug Combinations; D004576:Electromyography; D005106:Exploratory Behavior / Q000187:drug effects; D008297:Male; D008845:Microinjections; D051381:Rats; D011919:Rats, Inbred Strains; D013787:Thalamic Nuclei / Q000187:drug effects / Q000503:physiopathology*; D013997:Time Factors
D000596:Amino Acids; D021542:Amino Acids, Neutral; D004338:Drug Combinations; C013809:5-aminovaleric acid; D001418:Baclofen; D001640:Bicuculline