Labeled norepinephrine uptake and release in rat globus pallidus

Parathyroid hormone control of free cytosolic Ca2+ in the kidney

We have established a perifusion system to monitor free cytosolic calcium concentrations ([Ca2+]i) in mouse kidney slices, which presumably reflects in vivo status more accurately than renal cells in culture, by means of the fluorescent calcium indicators quin-2 and fura-2. An increase in the extracellular calcium concentrations from 0 (no added Ca2+) to 3.0 mM resulted in an increase in [Ca2+]i from 52 to 239 nM. Replacement of 118 mM of extracellular Na+ with choline, or the addition of ouabain, an inhibitor of Na+,K+-ATPase, at 10(-6) M in the perfusate caused an increase in [Ca2+]i from 161 +/- 13 to 873 +/- 78 nM (n = 10) and 161 +/- 13 to 395 +/- 68 nM (n = 4), respectively, suggesting the possible existence of a Na+,Ca2+ exchange mechanism in the kidney slice. We further examined the effects of PTH on [Ca2+]i mobilization in the kidney. Both human PTH-(1-34) and hPTH-(1-84) increased [Ca2+]i within 60 s at physiologic concentrations of 10(-11)-10(-9) M in a dose-dependent manner. On the other hand, an increase in intracellular cAMP in the slice was also detected above 3 X 10(-9) M hPTH-(1-34) [base 2.1 +/- 0.4 pmol/mg, 3.2 +/- 0.6 pmol/mg (p less than 0.05 versus control values) 5 minutes after the application of 3 X 10(-9) M hPTH-(1-34) and 17.3 +/- 4.3 pmol/mg (p less than 0.05 versus control values) 3 X 10(-8) M hPTH-(1-34), mean +/- SEM, n = 7, p less than 0.05 versus control values].(ABSTRACT TRUNCATED AT 250 WORDS)

Noradrenergic effects in tardive dyskinesia, akathisia and pseudoparkinsonism via the limbic system and basal ganglia

1. This paper proposes that the neuropsychiatric symptoms of tardive dyskinesia, akathisia and pseudoparkinsonian tremor are modulated by a noradrenergic pathway that projects from the locus coeruleus to the limbic system. 2. The proposed pathway is found to the consistent with neuroanatomical and neurochemical data in the literature. 3. The proposed pathway is found to be clinically consistent with observations by ourselves and others on the efficacy of clonidine and beta-adrenoreceptor blockers like propranolol for treating akathisia and pseudoparkinsonian tremor. It is also consistent with reports by ourselves and others that some patients with tardive dyskinesia benefit from treatment with propranolol or clonidine. 4. Noradrenergic modulation of the limbic system by way of the locus coeruleus accounts for a number of clinical observations, such as the worsening of tardive dyskinesia by stress, the greater risk for tardive dyskinesia in patients with affective disorder, the time-of-onset of tardive dyskinesia, and the coexistence of tardive dyskinesia and pseudoparkinsonism. 5. The functional significance of beta-adrenoreceptors in the basal ganglia is considered from an evolutionary perspective. 6. The model proposed in this article appears to have considerable heuristic value because it may further our understanding of Gilles de la Tourette syndrome and attention deficit disorder (hyperkinesis).

Lack of selectivity between the uptake of [3H]adrenaline and [3H]noradrenaline into rat hypothalamic slices

The uptake of [3H]adrenaline and [3H]noradrenaline into rat hypothalamic slices was compared for determination of whether adrenaline uptake was independent of uptake into noradrenergic neurones. Kinetic analysis revealed a similar high-affinity uptake process for both adrenaline and noradrenaline, with Km and Vmax values within similar ranges. These uptakes were inhibited by desipramine and maprotiline in a dose-dependent manner, but the selective dopamine and 5-hydroxytryptamine uptake inhibitors benztropine and fluoxetine, respectively, were without effect. Competition for uptake sites by unlabelled adrenaline with [3H]adrenaline and [3H]-noradrenaline and by unlabelled noradrenaline with [3H]-adrenaline and [3H]noradrenaline was very similar. Lesioning of the major adrenaline-containing cell group (C1 cell group) decreased the hypothalamic adrenaline concentration but had no effect on hypothalamic [3H]adrenaline or [3H]noradrenaline uptake. The results suggest that exogenous adrenaline is largely taken up by high-affinity sites on noradrenergic nerve terminals.

Differential behavioral effects of tryptophan and 5-hydroxytryptophan in vervet monkeys: influence of catecholaminergic systems

In previous studies tryptophan and 5-hydroxy-tryptophan (5-HTP) treatments produced opposite effects on aggression and vigilance and differing effects on eating and locomoting in vervet monkeys. This study examined the effects of the serotonin reuptake inhibitor fluoxetine, and the catecholamine reuptake inhibitor desmethylimipramine (DMI) on tryptophan and 5-HTP induced behavioral changes. Thirty-two adult males from 16 different social groups were studied. Tryptophan (10, 20, and 40 mg/kg/day) produced dose-dependent reductions in aggression, vigilance, and locomotion and increases in eating. In contrast, 5-HTP (20, 40, and 80 mg/kg/day) increased aggression and vigilance and did not affect locomotion or eating. Fluoxetine (0.5, 1.0, and 2.0 mg/kg/day) produced effects identical to tryptophan while DMI (1.5, 3.0, and 6.0 mg/kg/day) resulted in dose-dependent increases in aggression, vigilance, and locomotion, and decrements in eating. When combined with tryptophan, fluoxetine augmented and DMI diminished the effects of tryptophan on all behaviors. Fluoxetine decreased and DMI increased the effects of 5-HTP on aggression and vigilance. Thus concurrent DMI enhanced and concurrent fluoxetine reduced the differences between 5-HTP and tryptophan. These results suggest that 5-HTP's effects on catecholaminergic systems may underlie the differing behavioral effects of tryptophan and 5-HTP on behavior in a species closely related to humans.

Dopamine release and presynaptic dopaminergic regulation in guinea pig spinal cord

Using pharmacological approaches, we obtained evidence for the release of dopamine (DA) and its dopaminergic regulation in the guinea pig spinal cord. Electrical stimulation of the cord pieces increased the endogenous DA release and the efflux of [3H]dopamine [( 3H]DA) from tissues preloaded with [3H]DA. The evoked release of [3H]DA was current- and frequency-dependent and was prevented by tetrodotoxin (10(-6) M) or Ca2+-free medium containing EGTA (10(-4) M), while benztropine allowed a recovery of a more extensive amount of [3H]DA in the superfusing medium by inhibiting the reuptake process. The stimulated [3H]DA release was reduced by LY-171555, but not by SKF-38393 and 8-Br-cAMP. (-)Sulpiride enhanced the stimulated endogenous DA and [3H]DA release. (-)Sulpiride reversed the inhibition of evoked [3H]DA release induced by LY-171555, while SKF-38393 and 8-Br-cAMP did not affect LY-171555-induced inhibition of evoked [3H]DA release. These findings provide additional evidence for the neurotransmitter role of DA in the spinal cord of the guinea pig, and they strongly suggest the presence of presynaptic regulation of DA release via the dopamine receptor which is the D2 type.

Influence of hypoxia on release and uptake of neurotransmitters in guinea pig striatal slices: dopamine and acetylcholine

We studied the influence of hypoxia on the release of [3H]dopamine ([3H]DA) and [3H]acetylcholine ([3H]ACh), uptake of [3H]DA and [3H]choline and Ca2+-influx in guinea pig striatal slices. Tetrodotoxin (TTX)-sensitive and Ca2+-dependent electrically evoked release of [3H]DA was not affected by hypoxia, while spontaneous release of [3H]DA was rapidly increased. On the other hand, by hypoxia, the evoked [3H]ACh release gradually decreased and was diminished to about 45% 40 min later. Hypoxia suppressed the Vmax of [3H]DA uptake to one third and that of [3H]choline to half of the control values, but with no change in either of the Km values. Hypoxia reduced both the acetylation and the uptake of [3H]choline in slices preliminarily incubated with 3 mM or 25 mM K+ medium. Stimulation-induced Ca2+-influx was slightly suppressed and was 78.1% of the control values even after 40 min exposure to hypoxia. The Ca2+-dependent neurotransmitter release process itself appears to be well preserved against hypoxia as compared with the uptake process. Our findings imply that hypoxia could result in differential alterations of neural activity depending on the specific sensitivity of the presynaptic process of neurotransmission.

Epinephrine release and presynaptic alpha 2-adrenoceptic regulation in the guinea pig hypothalamus

The release of epinephrine (E) and its regulation system were investigated in the slices of guinea pig hypothalamus. Electrical stimulation produced an efflux of [3H]E from tissues preloaded with [3H]E, in a current- and frequency-dependent manner. Stimulated [3H]E release was inhibited by tetrodotoxin and by a calcium-free medium containing ethylene glycol bis(beta-aminoethylether)-N,N,N',N'-tetraacetic acid (EGTA). Stimulated [3H]E release was enhanced by yohimbine and this effect was suppressed by clonidine. These results provide strong evidence for the neurotransmitter role of E in the hypothalamus, and suggest the possible existence of regulatory mechanism of E release via presynaptic alpha 2-receptors.

Evidence for the neurotransmitter role of norepinephrine in the ventral thalamic nucleus of the guinea pig: localization, uptake and release

The localization, uptake and release of norepinephrine (NE) by the isolated guinea pig ventral thalamic nucleus (VT) were studied to determine the possible neurotransmitter role of this catecholamine. The NE content in the VT was 356 +/- 24 ng/g wet weight and intraneuronal localization of NE was demonstrated in the VT by histofluorescence. [3H]NE accumulation into the VT slices was about 3 times that of [3H]NE (10(-7) M) in the medium 10 min after incubation. Kinetic analyses indicated 2 components of [3H]NE accumulation, one representing a high (Km1 4 X 10(-7) M and Vmax1 1.5 pmol/mg/10 min) and a low (Km2 1.8 X 10(-6) M and Vmax2 5 pmol/mg/10 min) affinity uptake system. Desmethylimipramine (10(-5) M) reduced the high affinity uptake of [3H]NE by 30% of the control value. Electrical stimulation of the slices increased the efflux of [3H]NE from tissues preloaded with [3H]NE, in a current- and frequency-dependent fashion. The release of [3H]NE induced by stimulation of up to 1 mA was inhibited by tetrodotoxin (10(-6) M) or Ca-free medium containing EGTA (10(-4) M). These findings provide strong evidence for the neurotransmitter role of NE in the VT.