Involvement of CB1 and TRPV1 receptors of the ventrolateral periaqueductal gray in physical stress-evoked cardiovascular responses during in rats

Hypertensive pregnancy (HTNP) is a risk factor for future cardiovascular disease. Exaggerated cardiovascular responses to physical stress are also considered an independent marker of cardiovascular disease risk. However, there are limited data regarding the blood pressure (BP) responses to acute stress in women, who have a history of HTNP. Hence, the aim of the study is to compare BP responses to a physical stress in postmenopausal women with a history of HTNP to age- and parity-matched women with a history of normotensive pregnancy (NP). Beat-to-beat BP and heart rate was recorded in 64 postmenopausal women with [age = 58.5 (55.2, 62.2) yr, where values are the median, 25th percentile, and 75th percentile] and without [age = 59.4 (55.9, 62.4) yr] a history of HTNP before and during isometric handgrip (IHG) exercise (30% of maximal voluntary contraction) to fatigue. Muscle metaboreflex was measured during postexercise ischemia following IHG exercise. BP variables increased similarly in response to IHG exercise [systolic: NP = 11.5 (8.9, 17.6) %, HTNP = 11.3 (9.5, 15.9) %; diastolic NP = 11.2 (7.9, 13.3) %, HTNP = 9.5 (7.1, 14.3) %; mean blood pressure: NP = 9.8 (5.0, 13.6) %, and HTNP = 7.2 (4.4, 10.4) %] and postexercise ischemia [systolic: NP = 14.1 (10.3, 23.0) %, HTNP = 15.8 (10.6, 21.4) %; diastolic NP = 12.2 (4.8, 17.0) %, HTNP = 10.4 (5.3, 17.1) %; and mean blood pressure: NP = 11.1 (6.1, 17.9) %, HTNP = 9.4 (2.9, 14.8) %] in both groups. Although having a history of HTNP is associated with future cardiovascular disease risk, results from this study suggest that the risk may not be manifested through altered cardiovascular metaboreflex response to physical stressors.

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Nitric oxide within periaqueductal gray modulates glutamatergic neurotransmission and cardiovascular responses during mechanical and thermal stimuli

Neuroscience Research ◽

10.1016/j.neures.2004.10.003 ◽

2005 ◽

Vol 51 (1) ◽

pp. 93-103 ◽

Cited By ~ 15

Author(s):

Takeshi Ishide ◽

Ahmed Amer ◽

Timothy J. Maher ◽

Ahmmed Ally

Keyword(s):

Nitric Oxide ◽

Cardiovascular Responses ◽

Periaqueductal Gray ◽

Glutamatergic Neurotransmission ◽

Thermal Stimuli

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Role of ventrolateral periaqueductal gray neurons in the behavioral and cardiovascular responses to contextual conditioned fear and poststress recovery

Neuroscience ◽

10.1016/s0306-4522(02)00744-3 ◽

2003 ◽

Vol 116 (3) ◽

pp. 897-912 ◽

Cited By ~ 88

Author(s):

P Walker ◽

P Carrive

Keyword(s):

Conditioned Fear ◽

Cardiovascular Responses ◽

Periaqueductal Gray

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c-Fos expression in the midbrain periaqueductal gray during static muscle contraction

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.2000.279.6.h2986 ◽

2000 ◽

Vol 279 (6) ◽

pp. H2986-H2993 ◽

Cited By ~ 19

Author(s):

Jianhua Li ◽

Jere H. Mitchell

Keyword(s):

Skeletal Muscle ◽

Muscle Contraction ◽

Neuronal Cells ◽

Cardiovascular Responses ◽

Periaqueductal Gray ◽

Exercise Pressor Reflex ◽

Arterial Blood ◽

Static Contraction ◽

Afferent Inputs ◽

Pressor Reflex

The periaqueductal gray (PAG) of the midbrain is involved in the autonomic regulation of the cardiovascular system. The purpose of this study was to determine if static contraction of the skeletal muscle, which increases arterial blood pressure and heart rate, activates neuronal cells in the PAG by examining Fos-like immunoreactivity (FLI). Muscle contraction was induced by electrical stimulation of the L7 and S1 ventral roots of the spinal cord in anesthetized cats. An intravenous infusion of phenylephrine (PE) was used to selectively activate arterial baroreceptors. Extensive FLI was observed within the ventromedial region (VM) of the rostral PAG, the dorsolateral (DL), lateral (L), and ventrolateral (VL) regions of the middle and caudal PAG in barointact animals with muscle contractions, and in barointact animals with PE infusion. However, muscle contraction caused a lesser number of FLI in the VM region of the rostral PAG, the DL, L, and VL regions of the middle PAG and the L and VL regions of the caudal PAG after barodenervation compared with barointact animals. Additionally, the number of FLI in the DL and L regions of the middle PAG was greater in barodenervated animals with muscle contraction than in barodenervated control animals. Thus these results indicated that both muscle receptor and baroreceptor afferent inputs activate neuronal cells in regions of the PAG during muscle contraction. Furthermore, afferents from skeletal muscle activate neurons in specific regions of the PAG independent of arterial baroreceptor input. Therefore, neuronal cells in the PAG may play a role in determining the cardiovascular responses during the exercise pressor reflex.

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Central integration of muscle reflex and arterial baroreflex in midbrain periaqueductal gray: roles of GABA and NO

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.00163.2004 ◽

2004 ◽

Vol 287 (3) ◽

pp. H1312-H1318 ◽

Cited By ~ 8

Author(s):

Jianhua Li

Keyword(s):

Muscle Contraction ◽

Pressor Response ◽

Cardiovascular Responses ◽

Periaqueductal Gray ◽

Muscle Afferents ◽

Triceps Surae ◽

Reflex Response ◽

Arterial Baroreflex ◽

Pressor Reflex ◽

Change In Mean

It has been suggested that the midbrain periaqueductal gray (PAG) is a neural integrating site for the interaction between the muscle pressor reflex and the arterial baroreceptor reflex. The underlying mechanisms are poorly understood. The purpose of this study was to examine the roles of GABA and nitric oxide (NO) in modulating the PAG integration of both reflexes. To activate muscle afferents, static contraction of the triceps surae muscle was evoked by electrical stimulation of the L7 and S1 ventral roots of 18 anesthetized cats. In the first group of experiments ( n = 6), the pressor response to muscle contraction was attenuated by bilateral microinjection of muscimol (a GABA receptor agonist) into the lateral PAG [change in mean arterial pressure (ΔMAP) = 24 ± 5 vs. 46 ± 8 mmHg in control]. Conversely, the pressor response was significantly augmented by 0.1 mM bicuculline, a GABAA receptor antagonist (ΔMAP = 65 ± 10 mmHg). In addition, the effect of GABAA receptor blockade on the reflex response was significantly blunted after sinoaortic denervation and vagotomy ( n = 4). In the second group of experiments ( n = 8), the pressor response to contraction was significantly attenuated by microinjection of l-arginine into the lateral PAG (ΔMAP = 26 ± 4 mmHg after l-arginine injection vs. 45 ± 7 mmHg in control). The effect of NO attenuation was antagonized by bicuculline and was reduced after denervation. These data demonstrate that GABA and NO within the PAG modulate the pressor response to muscle contraction and that NO attenuation of the muscle pressor reflex is mediated via arterial baroreflex-engaged GABA increase. The results suggest that the PAG plays an important role in modulating cardiovascular responses when muscle afferents are activated.

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