FACTORS INFLUENCING BRAIN AND TISSUE LEVELS OF TRYPTAMINE: SPECIES, DRUGS AND LESIONS

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Abstract
—: With a modification of the spectrophotofluorometric (SPF) method of HESS & UDENFRIEND (1959) (J. Pharmac. exp. Ther.127, 175‐177), brain tryptamine levels in the rat (20.9 ng/g) and guinea‐pig (20.7 ng/g) were found to be less than those in the dog (32.1 ng/g) and cat (52.2 ng/g). Regional distribution studies in the dog and cat showed that tryptamine was present in all major brain regions with highest concentrations in the spinal cord. Blood levels of tryptamine in the guinea‐pig, dog and cat (6‐7 ng/ml) were lower than brain levels. Pargyline significantly increased brain tryptamine in both the dog and cat; whereas, isocarboxazid (after 4 h) increased brain tryptamine levels in the dog but decreased brain levels in the cat. Reserpine (0.5‐1.0 mg/kg per day for 1‐4 days) did not significantly decrease brain, spinal cord or blood tryptamine levels in the dog. Spinal cord transection did not decrease tryptamine levels below the lesion in the chronic spinal dog.