Mescaline increases startle responding equally in normal and raphe-lesioned rats
Mark A. Geyer, Gary J. Rose, Lyle R. Petersen
Pharmacology Biochemistry and Behavior February 1, 1979 DOI: 10.1016/0091-3057(79)90103-5 (opens in new tab)
Study at a glance
AI-extracted from the abstract| Characteristics | Observational study with experimental intervention Peer reviewed |
|---|---|
| Population | Rats |
| Intervention | Mescaline |
| Dose | 10 mg/kg |
| Duration | One week after lesion, then two test sessions on consecutive days |
| Measures | startle magnitude |
| Topics | Mescaline Serotonin |
| Keywords | Dorsal raphe nucleus Raphe nuclei Midbrain Median raphe nucleus Moro reflex Anesthesia |
| Citations | 7 |
| Key findings | Mescaline produced comparable 25% increases in startle magnitudes in both sham- and raphe-lesioned animals, failing to support the hypothesis that its effects are mediated by the midbrain raphe nuclei. |
Abstract
To test the possible involvement of serotonin-containing cells of the midbrain in mediating the effects of mescaline on startle responding, electrolytic lesions were made in either the dorsal or median raphe nucleus in rats. Decreases in either striatal or hippocampal tryptophan hydroxylase activity confirmed the effectiveness of the lesions. One week later, startle was measured in response to 30 air-puff stimuli for each rat. Median, but not dorsal, raphe lesions increased startle magnitudes throughout the test session. The following day each group was divided into matched halves and were given 60 trials, 30 minutes after intraperitoneal injection of either saline or 10 mg/kg mescaline. Despite the large differences in baseline startle among the groups, mescaline produced comparable 25% increases in startle magnitudes in both sham- and raphe-lesioned animals. This result fails to support the hypothesis that increased startle responding produced by mescaline is mediated by the midbrain raphe nuclei.