Midgut gland toxins of Hawaiian sea hares—II. A preliminary pharmacological study

Abstract

We report some preliminary studies on ether-soluble and water-soluble residues obtained from the midgut glands of two Hawaiian species of sea hares (Aplysiidae). Sublethal doses of the crude ether-soluble residue produce hypertension when injected intravenously into anesthetized rats, whereas the crude water-soluble residue produces a transient hypotension, bradycardia and apnea. Dose-effect curves for more purified extracts show actions similar to those seen with crude extracts. The hypertension produced by the ether-soluble toxin is resistant to both alpha- and beta-adrenergic blocking agents. The hypotensive effect of the water-soluble extract could not be abolished by vagotomy or pretreatment with either atropine (25 mg/kg) or Benadryl (22 mg/kg). It is concluded that both extracts may have direct effects on the contractility of vascular smooth muscle which are not mediated by alpha-adrenergic or cholinergic mechanisms. The possible relationship of these toxic extracts to the previously described aplysin is discussed.