Effects of morphine and neuroleptics on wet-dog shaking behavior elicited by hippocampal stimulation in rats.

The relationship between wet-dog shaking (WDS) and afterdischarge (AD) elicited by dorsal hippocampal stimulation was investigated. The number of the WDS during a 150-s observation period was 9.6 +/- 2.0 (mean +/- SEM) and no WDS was seen during the non-seizure period. The effects of morphine and neuroleptics on WDS and AD were also investigated. Morphine significantly inhibited the number of WDS elicited by hippocampal stimulation. Naloxone significantly antagonized the inhibitory effect of morphine. Haloperidol and chlorpromazine significantly and dose-dependently inhibited the number of WDS at very small doses. The inhibitory effect of chlorpromazine on WDS was not antagonized by pretreatment with naloxone. The present results suggest that central dopaminergic mechanisms may be important in WDS elicited by hippocampal stimulation. The effect of morphine on WDS is probably mediated via an opioid receptor having a modulating effect on central dopaminergic mechanisms.