Substance P and serotonin independently affect intragastric pressure when microinjected into the nucleus raphe obscurus of the rat.
We have recently shown that microinjection of substance P (SP) into the nucleus raphe obscurus (NRO) of the rat decreases intragastric pressure, whereas microinjection of serotonin (5-HT) increases it. The purpose of the present study was to investigate whether there exists a functional interaction between SP and 5-HT in the NRO of the rat in their effects on gastric motor function. This was accomplished by microinjection of SP (135 pmol) and 5-HT (0.6 and 6 nmol) into the NRO in a rapid, sequential order in alpha-chloralose-anesthetized rats, while monitoring intragastric pressure and pyloric and greater curvature motilities. Substance P evoked significant decreases in intragastric pressure when microinjected into the NRO after vehicle and after 5-HT (at both 0.6 and 6 nmol). There was no difference in the magnitude of the SP effect after 5-HT when compared to the response after vehicle. Serotonin at a dose of 6 nmol, but not at a dose of 0.6 nmol, elicited significant increases in intragastric pressure when microinjected after vehicle or after SP, and there was no difference between the responses to 5-HT with respect to the initial treatment. We conclude that SP and 5-HT act independently in the NRO of the rat to affect intragastric pressure.
Krowicki
Z K
ZK
Department of Pharmacology and Experimental Therapeutics, Louisiana State University Medical Center, New Orleans 70112, USA.
Hornby
P J
PJ
D000818:Animals; D008297:Male; D008845:Microinjections; D011312:Pressure; D011903:Raphe Nuclei / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012701:Serotonin / Q000494:pharmacology*; D013270:Stomach / Q000187:drug effects*; D013373:Substance P / Q000494:pharmacology*
D012701:Serotonin; D013373:Substance P