SYMPATHETIC THYROIDAL VASOCONSTRICTION IS NOT BLOCKED BY A NEUROPEPTIDE-Y ANTAGONIST OR ANTISERUM

Sympathetic nerve fibers to thyroid blood vessels contain both norepin ephrine (NE) and neuropeptide Y (NPY). To assess the involvement of en dogenous NPY in the sympathetic neural control of thyroid blood flow, appropriate doses of a selective NPY antagonist, alpha-trinositol, and an NPY antiserum (NPY-AS) were used during cervical sympathetic trunk stimulation in anesthetized rats. During all experiments, thyroid blo od flow was continuously monitored by laser Doppler blood flowmetry. N either a-trinositol nor NPY-AS blocked the thyroidal vasoconstriction evoked by either the first or second stimulation of the cervical sympa thetic trunks. Our results suggest that NPY is not involved either dir ectly or indirectly during acute sympathetic vasoconstriction in the r at thyroid gland.