A novel approach based on nanotechnology for investigating the chronic actions of short-lived peptides in specific sites of the brain

This review presents a novel experimental approach for investigating the chronic actions of short-lived peptides in specific sites of the brain. This method combines the advantages of three different techniques: liposome encapsulation, site-specific microinjection and telemetry. First, liposomes can be designed to remain located at the injection site for a long period of time, where they protect encapsulated peptide from rapid degradation and act as a sustained-release system. Secondly, microinjection allows the administration of peptides in specific sites of the brain with minimal side effects. Finally, using telemetry, it is possible to register physiological parameters and their circadian variations in undisturbed free-moving animals for several days. Angiotensin-(1–7) and angiotensin II were used as peptide models, in order to validate the proposed method. Following the unilateral microinjection of the liposome-encapsulated peptides into the rostral ventrolateral medulla (RVLM) of Wistar rats, long-lasting cardiovascular actions were elicited, for several days. Importantly, new physiological actions of angiotensin-(1–7) at the RVLM were unmasked: modulation of the circadian rhythms of blood pressure and heart rate. It is felt that this method can be applied to a wide variety of short-lived bioactive peptides and should encounter numerous applications in the field of neurosciences.