The mapped pattern of kainate on blood pressure responses is similar to that of L-proline in the ventrolateral medulla of the rat.
Kainate is an excitatory amino acid receptor agonist with a structure similar to the amino acid L-proline. Our previous studies demonstrated that microinjections of L-proline into the ventrolateral medulla (VLM) of the rat induce a mapped pattern of blood pressure responses distinct from L-glutamate, and the depressor response to L-proline in the caudal VLM (CVLM) is abolished by the kainate/AMPA receptor antagonist CNQX. The present study investigated whether kainate produces the L-proline-mapped pattern of responses in the VLM, compared with the pattern by AMPA. Kainate is known to activate AMPA receptors at higher concentrations. Therefore, responses to kainate were investigated at a low concentration. Microinjections of AMPA or NMDA showed the pattern of the L-glutamate-type; a pressor response in the rostral VLM and caudal pressor area (CPA) and a depressor response in the CVLM. Microinjections of kainate showed depressor responses in the CVLM but minor pressor responses in the rostral VLM, suggesting the same responses to L-proline. However, the response sites in the CPA did not enable us to clearly determine the L-proline-type. Further trials at sites defined by a pressor response to L-glutamate in the CPA, successive injections of L-proline and kainate produced no response, indicating that L-glutamate responding neurons in the CPA are not sensitive to L-proline and kainate. These results suggest that kainate stimulation in the VLM produces a mapped pattern of ABP responses similar to the mapped pattern with L-proline. Kainate receptors could therefore be involved in the depressor response to L-proline in the medulla.
Takemoto
Yumi
Y
Department of Neurophysiology, Graduate School of Biomedical Sciences, Hiroshima University, Kasumi 1-2-3, Minami-ku, Hiroshima 734-8551, Japan. yumitake@hiroshima-u.ac.jp
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects*; D001931:Brain Mapping; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology*; D007608:Kainic Acid / Q000494:pharmacology*; D008297:Male; D008526:Medulla Oblongata / Q000187:drug effects*; D008845:Microinjections; D011392:Proline / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar
D018690:Excitatory Amino Acid Agonists; D011392:Proline; D007608:Kainic Acid