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Endomorphin-2 in the medial NTS attenuates the responses to baroreflex activation
- Source :
- Brain Research. :365-373
- Publication Year :
- 2006
- Publisher :
- Elsevier BV, 2006.
-
Abstract
- We have previously reported that microinjections of endomorphin-2 (E-2; an endogenous mu-receptor agonist) into the medial subnucleus of the NTS (mNTS) elicit depressor and bradycardic responses via activation of ionotropic glutamate receptors located on secondary mNTS-neurons. Based on this report, it was hypothesized that activation of secondary mNTS neurons by E-2 may result in an exaggeration of baroreflex responses. In order to test this hypothesis, baroreflex responses were studied in adult, urethane-anesthetized, artificially ventilated, male Wistar rats before and after the microinjections of E-2 into the mNTS. Baroreceptors were stimulated by applying pressure increments (80-100 mm Hg) in the carotid sinus and by electrical stimulation (stimulus intensity: 0.5 V, frequencies 5, 10, and 25 pulses/s, pulse duration: 1 ms) of the aortic nerve for 30-s periods. Baroreceptor stimulation elicited depressor and bradycardic responses. Microinjections (100 nl) of E-2 (0.4 mmol/l) into the mNTS attenuated the baroreflex responses. Microinjections of naloxone (an opioid receptor antagonist) into the mNTS (0.5 mmol/l) did not alter baroreflex responses. Based on these results, it was concluded that activation of mu-opioid receptors in the mNTS attenuates baroreflex responses. Possible mechanisms for excitatory effects of E-2 in the mNTS resulting in depressor and bradycardic responses, on one hand, and inhibitory effects resulting in attenuation of baroreflex responses, on the other, are discussed.
- Subjects :
- Male
Agonist
medicine.medical_specialty
Time Factors
Baroreceptor
Microinjections
medicine.drug_class
Narcotic Antagonists
Models, Neurological
Glutamic Acid
Blood Pressure
Stimulation
Baroreflex
chemistry.chemical_compound
Heart Rate
Opioid receptor
Internal medicine
Solitary Nucleus
medicine
Animals
Rats, Wistar
Molecular Biology
Naloxone
business.industry
musculoskeletal, neural, and ocular physiology
General Neuroscience
Carotid sinus
Vagus Nerve
Electric Stimulation
Rats
Analgesics, Opioid
Carotid Sinus
Endocrinology
medicine.anatomical_structure
nervous system
chemistry
cardiovascular system
Neurology (clinical)
business
Oligopeptides
Endomorphin
circulatory and respiratory physiology
Developmental Biology
Subjects
Details
- ISSN :
- 00068993
- Database :
- OpenAIRE
- Journal :
- Brain Research
- Accession number :
- edsair.doi.dedup.....70226363f6b8b71044d807a6b7f3526b