Differential neurobehavioral effects of neurotensin and structural analogues

Neurobehavioral effects of neurotensin and structural analogues in which tyrosine in position 11 was replaced by either its d-isomer [D-Tyr11]-NT, phenylalanine [Phe11]-NT or D-phenylalanine [D-Phe11]-NT were studied. Results demonstrate that whereas neurotensin and [Phe11]-NT significantly decreased motor activity in rats, [D-Tyr11]-NT and [D-Phe11]-NT produced a marked and significant increase in activity. Such dichotomous action between analogues was not found for the hypothermic and muscular relaxation effects of neurotensin.