ABSTRACT
In the present work, we have shown electrochemically that in the rat olfactory bulb (OB), extracellular dopamine (DA) was highest in the glomerular layer (GL), whereas extracellular noradrenaline (NA) appeared to be more uniformly distributed across layers. The GL catecholamine (CA) responses to amphetamine (AMPH) and phenylethylamine (PEA) were also characterized electrochemically using an in vivo model. Results of this investigation show that at a lower dose (1 mg/kg), PEA had no effect on CA release. In contrast, at a higher dose (10 mg/kg), it produced similar increases in either extracellular DA (17.5 +/- 7%) or extracellular NA (14 +/- 3%), and DA exhibited dose-independent increases to AMPH (93 +/- 8%: 1 mg/kg vs. 97 +/- 6%: 10 mg/kg) whereas NA exhibited dose-dependent increases to AMPH (24.5 +/- 6%: 1 mg/kg vs. 39 +/- 7%: 10 mg/kg). These data indicate that (i) PEA may increase CA release but less efficiently than AMPH. (ii) AMPH is more efficient on the DAergic than on the NAergic system since AMPH-induced DA release exceeded 2-4 times the AMPH-induced NA release.
Subject(s)
Amphetamine/pharmacology , Dopamine/metabolism , Norepinephrine/metabolism , Olfactory Bulb/drug effects , Phenethylamines/pharmacology , Animals , Dose-Response Relationship, Drug , Male , Neurons/metabolism , Olfactory Bulb/metabolism , Olfactory Bulb/ultrastructure , Rats , Rats, WistarABSTRACT
Protein content and ATPase activities have been determined in the superficial and deep layers of the rat olfactory bulb. Protein levels, Mg2(+)-ATPase and Na+,K(+)-ATPase activities were significantly higher in the whole homogenate for the superficial layers. These differences were amplified when activity was expressed on a wet weight basis in a crude microsomal preparation isolated by differential centrifugation. Specific activities, however, showed similar values in the microsomal fractions from superficial and deep layers. The results are discussed in terms of differences in the density of neuronal processes and efficiency of K+ reuptake mechanisms.
Subject(s)
Olfactory Bulb/enzymology , Sodium-Potassium-Exchanging ATPase/metabolism , Animals , Ca(2+) Mg(2+)-ATPase/metabolism , Male , Rats , Rats, Inbred StrainsABSTRACT
gamma-Aminobutyric acid (GABA) and baclofen were iontophoresed into the glomerular and plexiform layers of the olfactory bulb of rats at different ages. Subsequent changes in K+ activity and mitral cell firing rates were monitored to specify GABA receptor activation. Only bicuculline-insensitive receptors are shown to be already present in the glomerular layer of the newborn rat. The possible distribution and maturation of GABA receptors on the olfactory nerve endings or on the dendrites of the mitral or periglomerular cells is discussed.
Subject(s)
Baclofen/pharmacology , Bicuculline/pharmacology , Olfactory Bulb/physiology , Potassium/physiology , gamma-Aminobutyric Acid/pharmacology , Action Potentials/drug effects , Animals , Olfactory Bulb/drug effects , Olfactory Bulb/growth & development , Rats , Rats, Inbred Strains , Receptors, GABA-A/drug effects , Receptors, GABA-A/physiologyABSTRACT
Using K+-sensitive microelectrodes inserted into the olfactory bulb, the effects of distant K+ ejection on the extracellular K+ activity (aK), were monitored in the glomerular and plexiform layers. A ouabain-sensitive mechanism, which appeared to be markedly more efficient in the glomerular layer, prevents spread of distal ejected K+. The results are discussed on the basis of Na+,K+-pump activation in both glomerular neuronal networks and the glial capsule enclosing each glomerulus.
Subject(s)
Olfactory Bulb/physiology , Potassium/physiology , Animals , Male , Membrane Potentials/drug effects , Olfactory Bulb/drug effects , Olfactory Bulb/enzymology , Ouabain/pharmacology , Potassium/pharmacokinetics , Rats , Rats, Inbred Strains , Sodium-Potassium-Exchanging ATPase/metabolismABSTRACT
Primary olfactory nerve stimulation induces a two-step increase in extracellular potassium, as recorded by K+-sensitive microelectrodes inserted into single glomeruli of the rat olfactory bulb. The second rise in K+ (K-peak) occurs in a graded, activity-dependent manner at the basal pole of the glomerular neuropile. This phenomenon appears to be directly related to the rate of extracellular K+ accumulation and is accompanied by a substantial depression of the mitral cell firing rate.
Subject(s)
Olfactory Nerve/physiology , Potassium/physiology , Animals , Electric Stimulation , Membrane Potentials/drug effects , Potassium/pharmacology , Rats , Rats, Inbred StrainsSubject(s)
Aging , Olfactory Bulb/physiology , Animals , Electric Stimulation , Food Deprivation , Neural Inhibition , Neurons/physiology , RatsSubject(s)
Olfactory Bulb/physiology , Synaptic Transmission , Age Factors , Animals , Calcium/pharmacology , Dominance, Cerebral/physiology , Electric Stimulation , Evoked Potentials/drug effects , Neural Inhibition/drug effects , Neurons/drug effects , Neurons/physiology , Olfactory Bulb/drug effects , Rats , Synaptic Transmission/drug effectsABSTRACT
Activities of adenylate cyclase, measured either in the absence or presence of sodium fluoride and Triton X-100, are determined in cerebral cortex and olfactory bulb homogenate of rats of 1 to 35 days of postnatal age. Differences in properties of the enzyme in the 2 structures are demonstrated.
Subject(s)
Adenylyl Cyclases/analysis , Cerebral Cortex/enzymology , Olfactory Bulb/enzymology , Age Factors , Animals , Animals, Newborn/metabolism , Cyclic AMP/biosynthesis , Rats , Sodium Fluoride/pharmacologyABSTRACT
Ontogenetic changes in calcium activity were directly measured using an ion-selective micropipette in rat blood plasma and olfactory bulb extracellular fluid. Significant differences were observed according to the age and the nutritional state of the animal.