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The mechanism of suppression of the baroreceptor response by the locus ceruleus in rats was investigated by probing the noradrenergic projections from this region of the brain to the paraventricular nucleus at the hypothalamus. Studies using agonists and antagonists of the neurotransmitters believed to act in the area revealed that the noradrenergic projections participate in the regulation of the baroreceptor response through alpha1-adrenergic receptors.

The physiological role of Fos protein expressed in the nucleus tractus solitarii (NTS) in central cardiovascular regulation was assessed through bilateral microinjection of antisense oligonucleotide into the caudal NTS of adult male rats. Results have shown that microinjection of oligonucleotide enhanced the spontaneous baroreceptor reflex response. The presence of expressed Fos protein at the NTS was critical to beat-to-beat baroreflex regulation of systemic arterial pressure.

A study was performed to compare the vasomotor element of the systemic arterial pressure (SAP) signals coming from the brain stem among brain-dead patients and patients in a vegetative state. Analysis of systolic blood pressure and interpulse interval was conducted in relation to cardiovascular regulatory mechanisms. Slow oscillations in SBP signals were noted in brain-dead patients compared with those in the vegetative state. Results of the study concluded that the vasomotor element of SAP signals and baroreflex was associated with brain stem functions.

The effects of exogenous application of angiotensin (ANG) II and III on the rostral nucleus reticularis ventrolateralis (NRVL) on the modulation of baroreceptor reflex (BBR) were analyzed in rat cerebellum. Microinjections of ANG II and ANG III in the rat NRVL inhibited BRR response in a dose-dependent manner. The inhibitory effects of ANG III were more significant at lower doses while ANG II was more potent in high doses. Furthermore, the tonic inhibitory response to ANG II and ANG III was caused by the depression of ANG type two receptors and increased glutamate levels.

The transfer function between the electrical stimulation of rostral nucleus reticularis ventrolateralis (NRVL) and response of systemic arterial pressure (SAP) was analyzed in Sprague-Dawley rats. Administration of phentolamine and yohimbine enhanced the magnitude of NRVL-SAP transfer functions in pentobarbital sodium-anesthetized rats. Furthermore, the low-pass pressor response to the activation of NRVL is characterized by the selective activation of the vasomotor component of SAP.

A modified model showing the relationship between respiration and systemic arterial pressure (SAP) is presented. This model is demonstrated using anesthetized rats as experimental animals. Unlike previous studies of the respiration-SAP relationship, this model includes an analysis of the transfer function between lung volume and SAP signals, and between lung volume and pulse pressure signals. A diagram of the experimental and analysis set-up is provided.

The role of the galanin (Gal) peptide in baroreceptor reflex (BRR) inhibition of heart rate by the hypothalamic paraventricular nucleus (PVN) was determined. A simulation of BRR inhibition was conducted using Sprague-Dawley rats. Immunohistochemical techniques revealed that suppression of the BRR was caused by the overlap of Gal-containing neurons in the PVN and in the site of electrical stimulation in the hypothalamic loci. It was suggested that galanin plays an important role in the regulation of cardiovascular control.

Pentobarbital is an anesthetic that possess suppressant actions on the cardiovascular system. Administration of pentobarbital in the rat caused mild hypertension and tachycardia, and very low dose-dependent suppression of systemic arterial pressure and heart rate. Continuous infusion of pentobarbital had no effect on normal cardiovascular functions. These results suggest that pentobarbital is an effective anesthetic that allows maintenance of cardiovascular regulation.

The periventricular nucleus (PVN) of the hypothalamus may be part of the outward pathway through which the locus cerulus (LC) evokes inhibition of the baroreceptor reflex (BRR). This pathway can also be activated through PVN alpha 1-adrenoceptors and neuropeptide A receptors. Adult male Sprague-Dawley rats were used to evaluate the potential role of the PVC of the hypothalamus in the suppression of BRR response by the LC. Electric stimulation of the LC evokes noticeable reduction in the BRR response.

The power spectral analysis of systemic arterial pressure (SAP) signals during cardiopulmonary bypass showing the different frequency components undergo differential changes at the various stages of the surgery. The contribution of vasomotor activity to SAP is given by the very low frequency component and it decreases slightly during hypothermic cardioplegia. The low, high, and very high components are eliminated for the time-period during the process.

Continuous, on-line, real-time analysis of the power spectrum (CORAPS) of systemic arterial pressure (SAP) signals provides an algorithm for power spectral analysis. The spectra of SAP signals, which portrays the cardiovascular activity, contains informative details about heart and blood vessels, as elucidated by the algorithm. The algorithm includes three window options aimed at improving the frequency or temporal resolution and distinguishing the spectral modifications seen during hypotension. The CORAPS algorithm serves as an important tool in monitoring acute hemodynamic changes.