Effects of angiotensin II on visual evoked potentials in the superior colliculus of juvenile rats

There are age-related changes in the relative expression of the AT(1) and A T(2) receptors of angiotensin II (Ang Il) in brain regions such as the supe rior colliculus, a midbrain visual structure where both receptor subtypes a re found. We investigated the effects of Ang II on gross visual activity in the colliculus of anesthetized rats aged between 15 and 35 post-natal days . Microinjection of Ang II in the superficial layers yielded a strong reduc tion in the amplitude of visual evoked potentials in a dose-related manner. Injection of the peptide in more ventral collicular layers did not modify the potential confirming the discrete localization of the angiotensinergic receptors in the superficial layers. Preliminary data indicated that the co -injection of Ang II with Losartan or PD 123319 yielded a partial blockade of Ang II suppressive effects, indicating that both AT(1) and AT(2) recepto rs are likely to be involved in mediating these responses. Overall, this st udy shows that the inhibitory nature of Ang II action is similar in juvenil e and adult animals (Merabet et at. 1994 and Merabet et al. 1997) (C) 2000 Harcourt Publishers Ltd.