Plants in the Solenace family have a history of use in traditional medicine for pain relief. We have shown that extracts from these plants induce significant and varying effects in rodent models of nociceptive responsivity [SFN 2004, 519.5], presumably resulting from the actions of anti-cholinergic alkaloids (i.e. scopolamine and atropine) found in such plants. Specifically, in rats, these extracts cause decreases in responsivity in hot-plate assays of thermal nociceptive response, increases in responsivity in tail-flick assays of spinal nociceptive responsivity, and both increases and decreases in specific nociceptive behaviors in the formalin assay of responsivity to a chronic, chemical irritant. The current study examined the effects of pure scopolamine-hydrobromide and scopolamine-methylbromide on nociceptive responsivity. Results show that systemic administrations of pure scopolamine-hydrobromide cause significant, dose-dependent nociceptive alterations paralleling results from whole-plant extracts. F...