Early postnatal administration of 5,7-dihydroxytryptamine: effects on substance P and thyrotropin-releasing hormone neurons and terminals in rat brain.
Substance P, thyrotropin-releasing hormone (TRH) and serotonin are putative neurotransmitters which have been proposed to co-exist in some brain neurons. Our previous immunocytochemical and biochemical studies have demonstrated that 85-100% of all serotonin neurons are destroyed following neonatal 5,7-dihydroxtryptamine (5,7-DHT) treatment. In this study, we have determined the effect of neonatal 5,7-DHT and desipramine (DMI) treatment on the biochemical content and immunocytochemical localization of substance P and TRH throughout the brain. Interestingly, we have observed that virtually all substance P- and TRH-immunoreactive cells in the ventral pons-medulla are destroyed by the neurotoxin. However, peptide-containing neurons in other regions were not affected. Additionally, we measured the peptide content and found that TRH is significantly decreased in the spinal cord (-50%) and pons-medulla (-20%), but not in other brain regions. Substance P content was not significantly altered in any region, even after a greater than 90% reduction of serotonin. These data indicate that the co-localized substance P and TRH forms a small proportion of the total peptide in brain.
Towle
A C
AC
Breese
G R
GR
Mueller
R A
RA
Hunt
R
R
Lauder
J M
JM
D015116:5,7-Dihydroxytryptamine / Q000494:pharmacology*; D000818:Animals; D000831:Animals, Newborn; D001921:Brain / Q000378:metabolism*; D004102:Dihydroxytryptamines / Q000494:pharmacology*; D007124:Immunoenzyme Techniques; D008526:Medulla Oblongata / Q000378:metabolism; D008636:Mesencephalon / Q000378:metabolism; D011149:Pons / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D013116:Spinal Cord / Q000378:metabolism; D013373:Substance P / Q000378:metabolism*; D013973:Thyrotropin-Releasing Hormone / Q000378:metabolism*
D004102:Dihydroxytryptamines; D015116:5,7-Dihydroxytryptamine; D013373:Substance P; D013973:Thyrotropin-Releasing Hormone