NEUROPHARMACOLOGY OF DELTA-AMINOLEVULINIC-ACID .1. EFFECT OF ACUTE ADMINISTRATION IN RODENTS

Delta-aminolevulinic acid (ALA) is suspected of being responsible for the neuropsychiatric symptoms of acute porphyria [in humans]. The effects of ALA were examined in vivo on a range of behavioral and physiological functions which are known to be affected in the acute porphyric attack. ALA was administered by i.p. or s.c. injection to mice in doses up to 1000 mg/kg, and effects on nociception (hot-plate and abdominal constriction tests), CNS excitability (pentobarbitone sleep-time and pentylenetetrazole-induced seizures), motor co-ordination and grip (rotating rod test) were studied. Rats were given i.v. injections or infusions of ALA of up to 24 mg and changes in blood pressure, heart rate and ED50 for noradrenaline, [norepinephrine], acetylcholine and isoprenaline examined. No statistically significant effects were noted, using buffered solutions of ALA (pH 7.0-7.4). Unbuffered solutions of ALA caused significant bradycardia and hypotension. Evidently, ALA has no significant acute neuropharmacological activity in vivo when the blood-brain barrier is intact.