Evidence that intracisternal injections of cholecystokinin-8 counteracts the cardiovascular effects of intracisternally injected adrenaline and neuropeptide Y in the alpha-chloralose anaesthetized rat.

Recently evidence has been obtained for the coexistence of adrenaline (A), neuropeptide Y (NPY) and cholecystokinin (CCK) in the same neurons located in the dorsal subnuclei of the nucleus tractus solitarius (nTS). Furthermore, receptor autoradiographical studies show a partial overlap between alpha 2, NPY and CCK receptors in this area. In the present study intracisternal (i.c.) co-administration of A/CCK-8 SO4 and NPY/CCK-8 SO4 was performed. Sulphated CCK-8 counteracted the hypotensive responses of NPY and A in the alpha-chloralose anaesthetized male rat. One possible explanation may be that the A/NPY/CCK neurons, which may be directly innervated by the baroreceptor afferents, release CCK peptides as endogenous antagonists to modulate the adrenergic/NPY-ergic transmission lines via a receptor-receptor interaction. An additional explanation is the possibility that the interaction between CCK, NPY and adrenaline takes place at the network level.