PMID- 1352860
OWN - NLM
STAT- MEDLINE
DCOM- 19920820
LR  - 20181130
IS  - 0028-3835 (Print)
IS  - 0028-3835 (Linking)
VI  - 55
IP  - 6
DP  - 1992 Jun
TI  - Repetitive injections of L-glutamic acid, in contrast to those of 
      N-methyl-D,L-aspartic acid, fail to elicit sustained hypothalamic GnRH release in 
      the prepubertal male rhesus monkey (Macaca mulatta).
PG  - 660-6
AB  - The purpose of the present study was to examine whether repetitive intravenous 
      injections of L-glutamic acid (Glu), like those of N-methyl-D,L-aspartic acid 
      (NMA), are able to elicit a sustained train of gonadotropin releasing hormone 
      (GnRH) discharges from the hypothalamus of the prepubertal male monkey. In order 
      to utilize pituitary luteinizing hormone (LH) secretion as a bioassay of 
      hypothalamic GnRH release, the responsiveness of the gonadotroph of the 
      prepubertal animals was enhanced prior to the study with a chronic intermittent 
      intravenous infusion of the synthetic decapeptide (0.1 microgram/min for 3 min 
      every h). Sequential intravenous injections of Glu (150 mg/kg BW) were 
      administered at 3-hour intervals for 6 or 24 h. Although the first injection of 
      this acidic amino acid elicited a robust discharge of GnRH, subsequent 
      stimulation with Glu resulted in GnRH discharges with progressively decreasing 
      magnitudes, and by the 9th injection Glu-induced GnRH release was abolished. Peak 
      concentrations of circulating Glu following the 1st and 4th Glu injection were 
      indistinguishable (3,959 +/- 437 vs. 4,139 +/- 72 nmol/ml, respectively). 
      Interestingly, the failure of repetitive intravenous injections of Glu to sustain 
      pulsatile GnRH release was not associated with a loss of responsiveness to NMA 
      administration, nor was it accompanied by a corresponding decrement in Glu 
      induced growth hormone (GH) discharges. As previously demonstrated, repetitive 
      intravenous administration of NMA (2-5 mg/kg BW) every 3 h for 9 h sustained 
      pulsatile GnRH secretion without decrement. A similar intermittent infusion of 
      kainic acid (KA; 1 mg/kg BW every 3 h for 6 h), however, elicited a GnRH response 
      that mimicked that observed in response to intermittent Glu treatment.(ABSTRACT 
      TRUNCATED AT 250 WORDS)
FAU - Medhamurthy, R
AU  - Medhamurthy R
AD  - Department of Physiology, University of Pittsburgh School of Medicine, Pa.
FAU - Gay, V L
AU  - Gay VL
FAU - Plant, T M
AU  - Plant TM
LA  - eng
GR  - HD08610/HD/NICHD NIH HHS/United States
GR  - HD13254/HD/NICHD NIH HHS/United States
PT  - Journal Article
PT  - Research Support, U.S. Gov't, P.H.S.
PL  - Switzerland
TA  - Neuroendocrinology
JT  - Neuroendocrinology
JID - 0035665
RN  - 0 (Glutamates)
RN  - 33515-09-2 (Gonadotropin-Releasing Hormone)
RN  - 3KX376GY7L (Glutamic Acid)
RN  - 6384-92-5 (N-Methylaspartate)
RN  - SIV03811UC (Kainic Acid)
SB  - IM
MH  - Animals
MH  - Biological Assay
MH  - Glutamates/*administration & dosage
MH  - Glutamic Acid
MH  - Gonadotropin-Releasing Hormone/*metabolism
MH  - Hypothalamus/*drug effects/metabolism
MH  - Injections, Intravenous
MH  - Kainic Acid/administration & dosage
MH  - Macaca mulatta
MH  - Male
MH  - N-Methylaspartate/*administration & dosage
MH  - Sexual Maturation/*physiology
MH  - Time Factors
EDAT- 1992/06/01 00:00
MHDA- 1992/06/01 00:01
CRDT- 1992/06/01 00:00
PHST- 1992/06/01 00:00 [pubmed]
PHST- 1992/06/01 00:01 [medline]
PHST- 1992/06/01 00:00 [entrez]
AID - 10.1159/000126186 [doi]
PST - ppublish
SO  - Neuroendocrinology. 1992 Jun;55(6):660-6. doi: 10.1159/000126186.