5-Methoxy-N,N-dimethyltryptamine: spinal cord and brainstem mediation of excitatory effects on acoustic startle.
Psychopharmacology – January 01, 1980
Source: PubMed
Summary
At doses starting from 0.12 mg/kg, 5-methoxy-N,N-dimethyltryptamine (5-MeODMT) significantly increased the acoustic startle reflex in rats, with effects peaking at the highest dose of 8.0 mg/kg. This increase in startle response was confirmed even in acutely decerebrate rats and when directly applied to the spinal cord. Notably, high doses' excitatory effects were entirely blocked by cinanserin, cyproheptadine, and propranolol, suggesting a complex interaction between serotonin receptors that differentially influence startle responses in the spinal cord and forebrain.
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.