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This Article Full Text Full Text (PDF) All Versions of this Article: 107/5/1591    most recent 90548.2008v1 Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Krause, K. L. Articles by Forster, H. V. PubMed PubMed Citation Articles by Krause, K. L. Articles by Forster, H. V.

µ-Opioid receptor agonist injections into the presumed pre-Bötzinger complex and the surrounding region of awake goats do not alter eupneic breathing

¹Department of Physiology, Medical College of Wisconsin, ; ²Department of Veterans Affairs Medical Center, and ; ³Department of Physical Therapy, Marquette University, Milwaukee, Wisconsin

Submitted 21 April 2008 ; accepted in final form 17 August 2009

Opioids are clinically important in the alleviation of pain. An undesirable side effect of opioids is depression of breathing. Data from isolated preparations suggest this effect is due to attenuation of discharge activity of neurons in the pre-Bötzinger complex (preBötzC), a medullary area with respiratory rhythmogenic properties. The purpose of this study was to examine how [D-Ala(2),N-Me-Phe(4),Gly(5)-ol]-enkephalin (DAMGO), a µ-opioid receptor agonist, affected breathing after injection into the presumed preBötzC of the adult awake goat. We hypothesized that DAMGO would cause breathing to decrease and become irregular when injected into the presumed preBötzC and the surrounding region of the conscious animal. We further hypothesized that ventilatory sensitivity to CO₂ and hypoxia would be blunted after the injection of DAMGO. Microtubules were bilaterally implanted into the presumed preBötzC of 10 adult female goats. After recovery from the surgery, DAMGO (0.5–10 µl, 1 nM–10 µM) was injected into the presumed preBötzC during the awake state. DAMGO had no effect on pulmonary ventilation [inspiratory minute ventilation (I)], respiratory rhythm and pattern, the activation pattern of inspiratory and expiratory muscles, or arterial blood gases during eupneic breathing conditions (P > 0.10). However, DAMGO attenuated (P < 0.05) the evoked increase in breathing frequency when inspired CO₂ was increased, and DAMGO attenuated the I response to reduction of inspired O₂ to 10.8% (P < 0.05). We conclude that our data do not provide support for the concept that in awake mammals opioid depression of breathing is due to a directed action of opioids on preBötzC neurons.

chemosensitivity; [D-Ala(2),N-Me-Phe(4),Gly(5)-ol]-enkephalin