Reserpine-induced depletion of neuropeptide Y in the guinea-pig: tissue-specific effects and mechanisms of action.

The effects of treatment with reserpine (5 mg.kg-1, s.c., 24 h prior to sacrifice) or 6-hydroxydopamine (6-OHDA; 250 mg.kg-1, s.c., for 4 days, one week before sacrifice) on the content of neuropeptide Y (NPY)-like immunoreactivity (LI) and noradrenaline (NA) were compared in a variety of tissues from the guinea-pig. Reserpine and 6-OHDA treatment markedly reduced the NA content of all peripheral organs investigated. Reserpine treatment also caused depletion of the content of NPY-LI in larger blood vessels and in organs containing mainly perivascular nerves. Furthermore, reserpine treatment depleted NPY-LI in the heart, spleen and adrenal gland. In other organs dominated by parenchymal adrenergic innervation such as genital organs (vas deferens, uterus) or iris, treatment with 6-OHDA but not reserpine caused significant depletions of NPY-LI. The urinary bladder and gastrointestinal tract seem to be mainly innervated by non-adrenergic NPY-containing neurons resistant to reserpine and 6-OHDA treatment. The content of NPY-LI was elevated in sympathetic ganglia after reserpine treatment while no increase in axonal transport occurred in the sciatic nerve. Cerebellum was the only studied area in the central nervous system where the NPY content was depleted by reserpine or 6-OHDA treatment suggesting presence of NPY-LI in perivascular nerves. The reserpine-induced depletion of NPY-LI in the spleen, kidney and skeletal muscle was prevented by preganglionic denervation. This suggests that enhanced nerve impulse discharge in sympathetic nerves caused a situation where NPY release exceeded the amount which could be replaced by axonal transport.(ABSTRACT TRUNCATED AT 250 WORDS)