Bradykinin microinjection in the paratrigeminal nucleus triggers neuronal discharge in the rat rostroventrolateral reticular nucleus.
A small collection of neurons in the dorsal lateral medulla, the paratrigeminal nucleus (Pa5), projects directly to the rostroventrolateral reticular nucleus (RVL). Bradykinin (BK) microinjections in the Pa5 produce marked pressor responses. Also, the Pa5 is believed to be a component of the neuronal substrates of the somatosensory response and the baroreflex arc. Considering the developing interest in the functional physiology of the Pa5, the present study was designed to characterize RVL neuronal activity in response to BK microinjections in the Pa5 as well as to phenylephrine-induced blood pressure increases in freely behaving rats. Of the 46 discriminated RVL neurons, 82% responded with a 180% mean increase in firing rate after BK application to the paratrigeminal nucleus, before the onset of the blood pressure increase. Thirty (79%) of the RVL BK-excited neurons were baroreceptor-inhibited units that responded with a 30% decrease in firing rate in response to a phenylephrine-produced increase of blood pressure. Twenty-seven (71%) units of the latter population displayed cardiac-cycle-locked rhythmic activity. The findings demonstrate a BK-stimulated functional connection between the Pa5 and RVL that may represent the neural pathway in the BK-mediated pressor response. This pathway may be relevant to baroreflex mechanisms since it relates to cardiovascular pressure-sensitive neurons.
Caous
Cristofer Andre
CA
Department of Biophysics, Escola Paulista de Medicina, Universidade Federal de São Paulo, SP, Brazil.
Balan
Antonio
A
Lindsey
Charles Julian
CJ
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D001920:Bradykinin / Q000008:administration & dosage / Q000494:pharmacology*; D008297:Male; D008526:Medulla Oblongata / Q000187:drug effects / Q000502:physiology*; D008845:Microinjections; D009474:Neurons / Q000187:drug effects* / Q000502:physiology; D010507:Periodicity; D010656:Phenylephrine / Q000494:pharmacology; D011311:Pressoreceptors / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar; D014279:Trigeminal Nucleus, Spinal / Q000187:drug effects / Q000502:physiology*
D010656:Phenylephrine; D001920:Bradykinin