Inhibitory effect of apomorphine on hippocampal stimulation-induced "wet-dog shakes" in rats may be due to a stereotyped behavior.
The effect of apomorphine on "wet-dog shakes" (WDS) elicited by hippocampal stimulation was investigated. Apomorphine in doses of 1.0 and 2.0 mg/kg given to rats s.c. reduced the number of WDS. Haloperidol in doses of 0.2-1.0 mg/kg given i.p. also significantly and dose-dependently reduced the number of WDS. The inhibitory effect of apomorphine in doses of 1.0 and 2.0 mg/kg on WDS was completely inhibited by haloperidol given in a dose of 0.5 mg/kg. It is, therefore, conceivable that the inhibition of WDS produced by apomorphine in doses of 1.0 and 2.0 mg/kg may result from the occurrence of stereotyped behavior and that the dopaminergic blocking action may be crucial for the inhibition of WDS induced by hippocampal stimulation. Despite a 50% increase in stimulation intensity, as compared with the afterdischarge threshold, the number of WDS remained unchanged. We tentatively concluded that apomorphine fails to increase the number of WDS, as a result of the ceiling phenomenon.
Araki
H
H
Department of Pharmacology, Taisho Pharmaceutical Co. Ltd., Saitama, Japan.
Uchiyama
Y
Y
Aihara
H
H
Yamamoto
T
T
Ohno
M
M
Ueki
S
S
D000818:Animals; D001058:Apomorphine / Q000494:pharmacology*; D004558:Electric Stimulation; D006220:Haloperidol / Q000494:pharmacology; D006624:Hippocampus / Q000502:physiology*; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D013239:Stereotyped Behavior / Q000187:drug effects / Q000502:physiology*
D006220:Haloperidol; D001058:Apomorphine