Maternal protein restriction affects cardiovascular, but not respiratory response to L-glutamate microinjection into the NTS of conscious rats

• Published in: Nutritional neuroscience 2021-11, Vol.24 (11), p.907-918
• Main Authors: Alves, D. S., Barbosa, D. F. S., Nogueira, V. O., Tourneur, Y., Fontes, D. A. F., Brito-Alves, J. L., Costa-Silva, J. H.
• Format: Article
• Language: English
• Subjects: acid kinurenic microinjection; Animals; Blood Pressure; cardiac variability; Cardiovascular System; Consciousness; Diet, Protein-Restricted; Female; glutamatergic system; Glutamic Acid - metabolism; Heart Rate - physiology; Humans; hypertension; L-glutamate microinjection; Maternal protein malnutrition; Microinjections; nucleus of the solitary tract; Pregnancy; Rats; Rats, Wistar; respiratory variability; Solitary Nucleus - metabolism
• ISSN: 1028-415X; 1476-8305
• DOI: 10.1080/1028415X.2019.1692508

Purpose: Dysregulation of glutamatergic neurotransmission (GN) is linked to sympathetic-respiratory overactivity and hypertension. We investigated whether maternal protein restriction is able to alter GN into the nucleus of the solitary tract (NTS) in adult offspring. Methods: Wistar rat dams were fed with control (NP; 17% protein) or low-protein (LP; 8% protein) diet during pregnancy and lactation, and their offspring were evaluated at 70-90d old. Direct measurements of mean arterial pressure (MAP), heart rate (HR), respiratory frequency (RF) and respiratory (RV) and cardiac (CV) variabilities were assessed in consciousness. The evaluation of GN into NTS over cardiovascular system were assessed by microinjections of unilateral glutamate (L-glu 0.5 nmol/100nL) and bilateral kynurenic acid (Kyn 2.5 nmol/50nL). The NP and LP groups were compared using unpaired Student's t-test where p < 0.05 was considered significant. Results: The LP exhibited higher MAP at rest (p = 0.03) and after L-glu microinjection (p = 0.04), as well as an increase over HR after Kyn microinjection when compared to the NP (p = 0.049). In the RV, the LP group showed an increase of the component-standard deviation 1 (p = 0.037) at rest. In the CV, the LP presented an increase of the low frequency (LF) component of the pulse interval (PI) (p = 0.034), a decrease of high frequency (HF) of the PI (p = 0.034), beyond an increased LF/HF ratio of the PI (p = 0.027) when compared to the NP. The kynurenic acid microinjection did not produce changes in RV or CV (p > 0.05). Conclusions: Altered GN into the NTS may contribute to augmented blood pressure in protein-restricted offspring.