Endogenous Content and Release of [3H]-GABA and [3H]-Glutamate in the Spinal Cord of Chronically Undernourished Rat

Abstract

The aim of this study was to determine the effect of chronic undernutrition on the content and release of γ-amino butyric acid (GABA) and glutamate (GLU) transmitters in the rat spinal cord. The release of [(3)H]-GABA and [(3)H]-GLU was determined by radioactive liquid scintillation techniques, and the concentrations of GABA and GLU in spinal cord preparations from control and undernourished young rats (50-60 days old) were measured by reverse-phase HPLC. The GABA and GLU contents in the lumbar spinal dorsal horn (L6 segment) were significantly lower in undernourished rats relative to control rats (22.2 ± 3.7 and 10.7 ± 1.9 %, respectively; P < 0.05). Spinal cord blocks from undernourished animals also showed lower rates of [(3)H]-GABA and [(3)H]-GLU release than controls (27.6 ± 3.5 and 12.8 ± 2.5 %, respectively; P < 0.01). We propose that the decreases in GLU content and release are consistent with a reduced activation of either afferent fibers, spinal glutaminergic neurons, or both. Furthermore, we propose that the decreased content and release of GABA in undernourished animals are related to a depression in pre- and post-synaptic inhibition. In addition, we hypothesize that the reductions in GABA content and release serve as compensatory mechanisms to counterbalance decreases in sensory transmission and GLU content in the spinal cord of the chronically undernourished rat.

Blockade of Intranigral and Systemic D3 Receptors Stimulates Motor Activity in the Rat Promoting a Reciprocal Interaction among Glutamate, Dopamine, and GABA

“…The separation of GABA and glutamate was achieved in a C18 column (particle size 2.7 µm, 4.6 mm width, and 100 mm long; SUPELCO Analytical (Sigma-Aldrich Co, St. Louis, MO, USA) with a mobile phase of 100 mM disodium hydrogen phosphate, 30% methanol, 3.5% acetonitrile, and pH 6.7 adjusted with phosphoric acid 70% at 32.5 °C. Both neurotransmitters were measured by precolumn derivatization with o-phthalaldehyde (OPA) [36,37]. Briefly, derivation was achieved by mixing 5 µL of working derivation solution (2.7 mg OPA, 10% methanol, 0.5 µL 2-β-mercaptoethanol (99%), and 90% 0.1 M sodium tetraborate buffer) with 35 µL of filtered microdialysis samples (nylon-membrane/0.45 lm pore size) and detected with a glassy carbon electrode VT-03 (Antec Leyden, Zoeterwoude, Netherlands) set at −550 mV (with respect to an Ag/AgCl reference electrode) [37].…”

“…Both neurotransmitters were measured by precolumn derivatization with o-phthalaldehyde (OPA) [36,37]. Briefly, derivation was achieved by mixing 5 µL of working derivation solution (2.7 mg OPA, 10% methanol, 0.5 µL 2-β-mercaptoethanol (99%), and 90% 0.1 M sodium tetraborate buffer) with 35 µL of filtered microdialysis samples (nylon-membrane/0.45 lm pore size) and detected with a glassy carbon electrode VT-03 (Antec Leyden, Zoeterwoude, Netherlands) set at −550 mV (with respect to an Ag/AgCl reference electrode) [37]. For DA separation, 25 µL of microdialysis samples was injected into a C18 column (particle size 2.7 µm, 4.6 mm width, and 100 mm long; SUPELCO Analytical from Sigma-Aldrich Co (St. Louis, MO, USA)) with mobile phase (monocloroacetic acid 100, EDTA 0.507, 1-octanosulfonic acid 0.767 (in mM), and acetonitrile 4.5%, pH NaOH adjusted to 3.2), coupled to a Waters 2475 Multi λ Fluorescence Detector (Waters Corporation, Milford, MA, USA), λx 279 nM, and λe 320 nM [36].…”

Effects provoked by chronic undernourishment on the fibre type composition and contractility of fast muscles in male and female developing rats

“…Two groups of female Wistar rats (mean body weight: 257.4 ± 16.3 g) were subjected to the following feeding conditions: (i) Control group (C): Adult female rats ( n = 16) and their offspring had free access to commercial food (Formulab 5008, Lab diet, Framingham, MA, USA). (ii) Chronic undernourished rats (U): Adult female rats ( n = 18) were fed with approximately half of the mean food intake of the control animals, starting 2 weeks before mating and continuing during pregnancy and lactation (Quiróz‐González et al., ). At the second post‐partum day, both the gender and number of pups in the offspring were determined (litter size: Control: 14.3 ± 1.5 puppies [5.5 ± 2.4 males and 8.8 ± 2.7 females]; Undernourished: 13.3 ± 1.1 puppies [6.6 ± 1.5 males and 6.6 ± 2.0 females]), adjusted to nine pups per litter (5 males and 4 females) and weighted (males: CM: 6.4 ± 0.1 g, UM: 6.2 ± 0.3 g; Females: CF: 6.1 ± 0.3 g; UF: 5.7 ± 0.3 g).…”

Hypothalamic A11 Nuclei Regulate the Circadian Rhythm of Spinal Mechanonociception through Dopamine Receptors and Clock Gene Expression

“…Each segment was homogenized in 0.1 N perchloric acid (200 µL per sample) and centrifuged at 3000 rpm for 3 min. The pellets were washed and resuspended in 1 N NaOH, and the amount of total protein in each sample was determined using the Bradford method and processed according to Quiroz et al [32]. The supernatant was analyzed via electrochemical detection using a high-pressure liquid chromatography (HPLC) system [33].…”