Bradycardic responses to microinjection of N-methyl-D-aspartate into the nucleus tractus solitarius are inhibited by local activation of 5-HT(3) receptors.

Previous reports have described that glutamate ionotropic receptors in the nucleus tractus solitarius (NTS) are involved in the reflex control of heart rate, and that such a control can be inhibited by NTS-5-HT(3) receptor stimulation. In the present study, we examined in urethane anaesthetized rats the effects of intra-NTS microinjection of 1-(m-chlorophenyl)-biguanide (CPBG), a potent and selective 5-HT(3) receptor agonist, on the cardiovascular responses to local administration of glutamate ionotropic receptor agonists. Intra-NTS microinjection of CPBG reduced the atropine-sensitive bradycardia elicited by local microinjection of NMDA without affecting the cardiovascular responses to intra-NTS microinjections of AMPA or kainic acid. The reduction by CPBG of the NMDA-evoked cardiac response was blocked by prior intra-NTS microinjection of granisetron, a 5-HT(3) receptor antagonist, as well as bicuculline, a GABA(A) receptor antagonist. These results suggest that the stimulation of NTS 5-HT(3) receptors specifically reduces, via a GABA-dependent mechanism, the cardiac response to local NMDA administration.

[Percutaneous coronary angioscopy: 200 observations in 100 candidates for angioplasty]. / Angioscopía coronaría percutánea: 200 observaciones en 100 pacientes candidatos a angioplastía.

Due to the recent technological advances, it is possible to perform percutaneous coronary angioscopy in a straightforward fashion in most patients. To know the safety and usefulness of this technique we present 200 observations in 100 patients candidates for coronary intervention. We used a coronary angioscope (Baxter, Edwards LIS Division), that can be placed using the conventional technique for percutaneous coronary angioplasty. The system incorporates a proximal occluding balloon, and distally a movable optical fiber. Case selection considered non-ostial coronary segments relatively straight. It was possible to obtain adequate images in 86 percent of cases. The technique is safe in experienced hands: there were two cases of ventricular fibrillation, and two cases of local dissection occurred, none of these associated with clinical consequences. No myocardial infarction, surgery or death, related to this procedure occurred. Valuable diagnostic information is derived from angioscopy as the method provides some histopathological correlation. Stable plaques are usually uniformly white or yellow. Unstable plaques are yellow and ulcerated. Thrombus can be easily recognized in acute coronary syndromes. Also in percutaneously treated segments, the final result and the presence of dissection or hemorrhage can be visualized. Coronary percutaneous angioscopy is safe and brings useful clinical information. Its applications in the clinical practice are still to be determined.