Cardiovascular mechanisms activated by microinjection  of baclofen into NTS of conscious rats

Landulpho, Carlos Daniel Almeida Pitanga; Dias, Ana Carolina; Colombari, Eduardo

doi:10.1152/ajpheart.00447.2002

Cited by 15 publications

(9 citation statements)

References 30 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…The notion that this pathway is involved is supported by the current observations that microinjection of baclofen into the NTS increases renal sympathetic nerve activity in both SHR and WKY rats and that the sympathoexcitatory response to baclofen is enhanced in SHR. This hypothesis is also supported by studies from other research groups that show the pressor response to baclofen microinjected into the NTS is attenuated by a vasopressin antagonist (20). In addition, the NTS is well known as a termination site for primary afferent fibers from baroreceptors and other peripheral cardiovascular receptors that contain blood pressure-sensitive neurons.…”

Section: Discussionsupporting

confidence: 65%

GABA<sub>B</sub> Receptor Gene Transfer Into the Nucleus Tractus Solitarii Induces Chronic Blood Pressure Elevation in Normotensive Rats

Liu

Xuan

et al. 2013

Circ J

View full text Add to dashboard Cite

Background Increasing evidence indicates that GABAergic neurons in the nucleus of the solitary tract (NTS) play a significant role in the arterial baroreceptor reflex and in the control of cardiovascular homeostasis. However, the role of these neurons in the development of hypertension is not yet fully clear. Methods and Results In the present study, we first confirmed that GABA B receptor (GBR) expression is enhanced in the NTS of SHR as compared with WKY rats using real time RT-PCR and Western Blots. To study the functional consequence of upregulated GBR expression, GBR was overexpressed in the NTS by bilateral microinjection of the AAV2-GBR1 viral vector into the NTS of WKY rats. Immunofluorescence staining and Western blots demonstrated that microinjection of AAV2-GBR1 into the NTS of WKY rats resulted in a significant increase in GBR1 expression in the NTS neurons. Overexpression of GBR in the NTS induced a chronic elevation in blood pressure and heart rate in the normotensive WKY rats. In an acute study, the pressor response to baclofen microinjected into the NTS was enhanced in SHR as compared with WKY rats. Conclusion GBR1 expression is enhanced in the NTS of SHR versus WKY rats and overexpression of this gene in the NTS results in chronic elevation of blood pressure and heart rate in normotensive rats.

show abstract

Section: Discussionsupporting

confidence: 65%

GABA<sub>B</sub> Receptor Gene Transfer Into the Nucleus Tractus Solitarii Induces Chronic Blood Pressure Elevation in Normotensive Rats

Liu

Xuan

et al. 2013

Circ J

View full text Add to dashboard Cite

show abstract

“…During exercise, Potts et al (45) showed that electrically evoked muscular contraction inhibits arterial baroreceptor signaling within the nucleus of the tractus solitarius (NTS) via activation of GABAergic receptors in rats, suggesting that skeletal muscle afferents are a potential source of synaptic drive to GABAergic neurons within the NTS. Indeed, GABA activation in conscious rats induces pressor response and tachycardia (8,31). However, the extent to which these findings can be extrapolated to humans remains unclear.…”

Section: Introductionmentioning

confidence: 99%

GABAergic contribution to the muscle mechanoreflex-mediated heart rate responses at the onset of exercise in humans

Teixeira

Ramos

Samora

et al. 2018

American Journal of Physiology-Heart and Circulatory Physiology

Self Cite

View full text Add to dashboard Cite

Previous studies have indicated that central GABAergic mechanisms are involved in the heart rate (HR) responses at the onset of exercise. On the basis of previous research that showed similar increases in HR during passive and active cycling, we reasoned that the GABAergic mechanisms involved in the HR responses at the exercise onset are primarily mediated by muscle mechanoreceptor afferents. Therefore, in this study, we sought to determine whether central GABA mechanisms are involved in the muscle mechanoreflex-mediated HR responses at the onset of exercise in humans. Twenty-eight healthy subjects (14 men and 14 women) aged between 18 and 35 yr randomly performed three bouts of 5-s passive and active cycling under placebo and after oral administration of diazepam (10 mg), a benzodiazepine that produces an enhancement in GABA activity. Beat-to-beat HR (electrocardiography) and arterial blood pressure (finger photopletysmography) were continuously measured. Electromyography of the vastus lateralis was obtained to confirm no electrical activity during passive trials. HR increased from rest under placebo and further increased after administration of diazepam in both passive (change: 12 ± 1 vs. 17 ± 1 beats/min, P < 0.01) and active (change: 14 ± 1 vs. 18 ± 1 beats/min, P < 0.01) cycling. Arterial blood pressure increased from rest similarly during all conditions ( P > 0.05). Importantly, no sex-related differences were found in any variables during experiments. These findings demonstrate, for the first time, that the GABAergic mechanisms significantly contribute to the muscle mechanoreflex-mediated HR responses at the onset of exercise in humans. NEW & NOTEWORTHY We found that passive and voluntary cycling evokes similar increases in heart rate and that these responses were enhanced after diazepam administration, a benzodiazepine that enhances GABA activity. These findings suggest that the GABAergic system may contribute to the muscle mechanoreflex-mediated vagal withdrawal at the onset of exercise in humans.

show abstract

“…Intra-NTS microinjections of GABA produce an increase in blood pressure and heart rate, which can also be evoked by microinjections of GABA A as well as GABA B receptor agonists into this nucleus [10,15,51,102,198,199,201]. It has been proposed that GABA A/B receptor-mediated pressor responses are due to an attenuation of the processing of baroreflex messages [51].…”

Section: Gabamentioning

confidence: 99%

The Key Role of Medullary 5-HT3 Receptors in the Serotonin-Mediated Neural Control of Cardiovascular Function

Sévoz‐Couche¹,

Machado²,

Hamon³

et al. 2005

View full text Add to dashboard Cite

The baroreceptor reflex plays a crucial role in the homeostatic control of cardiovascular parameters. In the central nervous system, the nucleus of the tractus solitarius (NTS) is critically involved in cardiovascular reflex control because it is both the first site of termination of glutamatergic baroreceptor afferent fibres and an important integrative area for the sensory afferent signals reaching the brainstem. In addition to glutamate, the NTS contains numerous neurotransmitters that could participate in the modulations of the baroreceptor reflex sensitivity which occur under various physiological conditions. In particular, a large body of evidence indicates that serotonin plays a modulatory role in the central control of blood pressure, especially at the level of the NTS, which is innervated by both central and peripheral serotonergic fibres. Indeed, serotonin exerts multiple cardiovascular influences through the activation of several receptors in the NTS. Actually, the NTS is the central area endowed with the highest density of serotonin 3 (5-HT 3 ) receptors whose stimulation triggers all the adaptive cardiovascular changes normally associated with behavioural responses to various stressful conditions.In this review, we first assess the current knowledge about the mechanisms underlying the cardiovascular effects of the specific activation of serotonergic receptors in the NTS. Secondly, we describe evidence that, in the NTS, 5-HT 3 receptors play a key role in one of the crucial homeostatic responses that characterise the defence reaction: the inhibitory modulation of the parasympathetic cardiac component of the baroreceptor reflex. The possible functional interactions of 5-HT 3 receptors with GABA A , NK 1 and NMDA receptors within the NTS are also discussed.

show abstract

Cardiovascular mechanisms activated by microinjection of baclofen into NTS of conscious rats

Cited by 15 publications

References 30 publications

GABA<sub>B</sub> Receptor Gene Transfer Into the Nucleus Tractus Solitarii Induces Chronic Blood Pressure Elevation in Normotensive Rats

GABA<sub>B</sub> Receptor Gene Transfer Into the Nucleus Tractus Solitarii Induces Chronic Blood Pressure Elevation in Normotensive Rats

GABAergic contribution to the muscle mechanoreflex-mediated heart rate responses at the onset of exercise in humans

The Key Role of Medullary 5-HT3 Receptors in the Serotonin-Mediated Neural Control of Cardiovascular Function

Contact Info

Product

Resources

About