5-Methoxy-N,N-dimethyltryptamine: spinal cord and brainstem mediation of excitatory effects on acoustic startle.
M Davis, D I Astrachan, P M Gendelman, D S Gendelman
Psychopharmacology January 1, 1980 DOI: 10.1007/BF00435302 via PubMed
Summary
AI-generated from the abstractThe drug 5-MeODMT, which acts on serotonin receptors, increased the acoustic startle reflex in rats starting at a dose of 0.12 mg/kg, with the effect growing stronger up to the highest dose tested (8.0 mg/kg). This enhancement occurred even in rats whose brains had been disconnected from the spinal cord or when the drug was applied directly to the spinal cord, indicating the effect originates in the spinal cord. Several serotonin-blocking drugs (cinanserin, cyproheptadine, propranolol) completely blocked this excitatory effect, while others did not. The findings support a theory that serotonin receptors in the spinal cord amplify startle, while those in the forebrain dampen it.
Study at a glance
| Characteristics | Experimental study Peer reviewed |
|---|---|
| Population | Rats |
| Interventions | 5-methoxy-N N-dimethyltryptamine (5-MeODMT) |
| Dose | 0.03, 0.06, 0.12, 0.25, 1.0, 2.0, 4.0, and 8.0 mg/kg body weight |
| Citations | 39 |
| Key finding | 5-MeODMT increased the acoustic startle reflex in rats in a dose-dependent manner starting at 0.12 mg/kg, an effect that originates in the spinal cord and is blocked by certain serotonin antagonists. |
Abstract
The effects of different doses (0.03, 0.06, 0.12, 0.25, 1.0, 2.0, 4.0, and 8.0 mg/kg body weight) of 5-methoxy-N,N-dimethyltryptamine (5-MeODMT) were tested on the acoustic startle reflex in rats. Beginning at 0.12 mg/kg, 5-MeODMT increased startle monotonically up to the highest dose used. 5-MeODMT still increased startle in acutely decerebrate rats or when infused directly onto the spinal cord. The excitatory effects of a high systemic dose of 5-MeODMT were completely blocked by cinanserin, cyproheptadine, and propranolol, but not by parachlorophenylalanine, alpha-methyl-p-tyrosine, haloperidol, sotalol, or phenoxybenzamine. The results were discussed in terms of a new theory, which suggests that stimulation of serotonin receptors in the spinal cord enhance startle whereas serotonin receptors in the forebrain inhibit startle.