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

ABSTRACT

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.

KEYWORDS:

• Maternal protein malnutrition
• hypertension
• nucleus of the solitary tract
• glutamatergic system
• L-glutamate microinjection
• acid kinurenic microinjection
• respiratory variability
• cardiac variability

Acknowledgments

We thank Fundação de Amparo à Ciência e Tecnologia de Pernambuco for financial support.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by Conselho Nacional de Desenvolvimento Científico e Tecnológico: [Grant Number 484452/ 2011-8; 459341/2014-6] and Fundação de Amparo à Ciência e Tecnologia de Pernambuco: [Grant Number IBPG 1436-4.05/14; PRONEM 0797-4.05/14; APQ 1365-2.07/10; APQ 1312-4.05/15].

Notes on contributors

D. S. Alves

D. S. Alves is a Nutritionist from the Federal University of Pernambuco (UFPE), Master in Nutrition, Physical Activity and Phenotypic Plasticity, and PhD student in Nutrition (UFPE).

D. F. S. Barbosa

D. F. S. Barbosa is Physical Educator from the Federal University of Pernambuco (UFPE).

V. O. Nogueira

V. O. Nogueira is Biologist from the Federal University of Pernambuco (UFPE), Master in Neuropsychiatry and Behavioral Sciences (UFPE) and Ph.D. in Nutrition (UFPE). Professor at Nutrition Department and researcher at the Laboratory of Nutrition, Physical Activity and Phenotypic Plasticity (UFPE).

Y. Tourneur

Y. Tourneur is an Engineer from Claude Bernard Lyon-1 University (UCBL), Ph.D. in Biological Sciences from UCLB.

D. A. F. Fontes

D. A. F. Fontes is a Pharmacist from the Federal University of Pernambuco (UFPE), Master and Ph.D. in Pharmaceutical Sciences from UFPE. Researcher at the Laboratory of Drug Technology, Department of Pharmacy, UFPE.

J. L. Brito-Alves

J. L. Brito-Alves is a Nutritionist from the Federal University of Pernambuco (UFPE), Master in Nutrition (UFPE), and Ph.D. in Neuropsychiatry and Behavioral Sciences (UFPE). Professor at Nutrition and researcher at Nutrition Department from Federal University of Paraíba (UFPB).

J. H. Costa-Silva

J. H. Costa-Silva is a Pharmacist from the Federal University of Pernambuco (UFPE), Master in Pharmaceutical Sciences from UFPE, and Ph.D. in Physiology from São Paulo University (USP). Professor at Sports Sciences Department and researcher at the Laboratory of Nutrition, Physical Activity and Phenotypic Plasticity (UFPE).