Biomedical subjects

M C Austin

Publications and source records attributed to M C Austin.

42 records · Page 3Linked to original sources

PubMed1990

Tyrosine hydroxylase and galanin mRNA levels in locus coeruleus neurons are increased following reserpine administration.

The neuropeptide galanin coexists in 80-90% of the norepinephrine-containing neurons in the locus coeruleus. In situ hybridization histochemistry was used to examine the effects of reserpine treatment or swim stress on tyrosine hydroxylase and galanin mRNA concentrations in locus coeruleus neurons. Reserpine administration significantly increased tyrosine hydroxylase and galanin mRNA levels in the locus coeruleus. The reserpine-induced increase in tyrosine hydroxylase mRNA was significantly correlated with the reserpine-induced increase in galanin mRNA. Three consecutive days of swim stress did not significantly alter either tyrosine hydroxylase or galanin mRNA concentrations in the locus coeruleus. These data suggest that both tyrosine hydroxylase and galanin gene expression in locus coeruleus neurons may be regulated by a reserpine-sensitive mechanism.

Animals↗

PubMed1990

Activity of centrally administered galanin fragments on stimulation of feeding behavior and on galanin receptor binding in the rat hypothalamus.

Synthetic fragments of galanin 1-29 were administered intraventricularly or into the paraventricular nucleus of the hypothalamus for analysis of the critical amino acid sequence necessary to stimulate feeding behavior in rats. Galanin 1-29 and galanin fragment 1-16 significantly increased feeding at doses of 6 nmol microinjected into the lateral ventricles and 1 nmol microinjected into the hypothalamus. There was no significant effect of D-TRP2 galanin 1-16 microinjected into the hypothalamus, and no significant effect of galanin fragments 1-9, 10-20, 12-29, 17-29, or 21-29 microinjected intraventricularly, on food consumption. Synthetic fragments of galanin 1-29 were assayed for displacement of 125I-galanin 1-29 binding to rat hypothalamic membranes. The efficacies of the galanin fragments in the feeding paradigm were consistent with the relative affinities of these fragments for the hypothalamic galanin receptor in equilibrium binding experiments. The first 16 N-terminal amino acids appear to contain galanin agonist activity on increasing food consumption and to bind to the galanin receptor in the rat hypothalamus.

Animals↗

PubMed1990

Enkephalinergic and GABAergic modulation of motor activity in the ventral pallidum.

Injection of the mu-opioid receptor agonist, Tyr-D-Ala-Gly-NMe-Phe-Gly-ol (DAMGO), produced a dose-dependent increase in horizontal motor activity after injection into the ventral pallidum or substantia innominata (VP/SI) of the rat. INjection of the delta-opioid receptor agonist, [D-Pen2,5]-enkephalin, produced a markedly reduced motor stimulant action, as did injection of DAMGO outside the VP/SI. Injection of the GABAA receptor antagonist, bicuculline, or the antagonist of the GABAA chloride channel, picrotoxin, also produced a dose-related elevation in horizontal motor activity. In contrast, the GABAB receptor antagonist, phaclofen, was without effect. The motor stimulant actions of both DAMGO and picrotoxin were attenuated by pretreatment in the VP/SI with the GABAA receptor agonist, muscimol. In contrast, pretreatment with the opioid receptor antagonist, naloxone, abolished only the actions of DAMGO on motor activity. These data demonstrate that motor activity can be regulated in the VP/SI by mu-opioid and GABAA neurotransmission, and that the response to mu-opioids can be modulated by GABAergic transmission.

Animals↗

PubMed1989

Blockade of enkephalinergic and GABAergic mediated locomotion in the nucleus accumbens by muscimol in the ventral pallidum.

The mu-opioid agonist, DAGO, and the indirect GABAA antagonist, picrotoxin, produced a dose-dependent increase in horizontal motor activity following injection into the nucleus accumbens that was independent of dopamine release. Injection of muscimol into the ventral pallidum antagonizes the motor stimulant effect of dopamine agonists. It was shown that muscimol abolished the locomotor stimulant effect of DAGO microinjection into the nucleus accumbens, and partially antagonized the effect of picrotoxin.

Animals↗

PubMed1988

The effect of cholinergic stimulation in the nucleus accumbens on locomotor behavior.

The present study was designed to investigate the effect of cholinergic stimulation of the nucleus accumbens (NA) on locomotor behavior. Microinjection of the cholinergic agonist, carbachol, into the NA resulted in a dose-dependent increase in spontaneous locomotor activity. Pretreating rats with the nicotinic antagonist, mecamylamine, significantly reduced the carbachol-induced locomotor response, whereas pretreatment with the muscarinic antagonist, atropine, was ineffective. Injection of the dopamine antagonist, haloperidol, prior to stimulation of the NA with carbachol, significantly attenuated the motor stimulant effect of carbachol. Evidence has accumulated to suggest that the increased locomotor response elicited from NA stimulation is mediated by GABAergic efferents from the NA to the substantia innominata (SI). Pretreatment with the GABA agonist, muscimol, into the SI significantly antagonized the locomotor hyperactivity induced by carbachol injection into the NA. Taken together, these data indicate that carbachol produces a motor stimulant effect by activating nicotinic receptors which may modulate the release of dopamine in the NA and inhibit the GABAergic efferents to the SI.

Animals↗

PubMed1986

Nuclear scanning in the diagnosis and localization of parathyroid adenomas.

Technetium-thallium nuclear scanning was performed in 17 patients whose clinical and biochemical findings were suggestive of the presence of hyperparathyroidism. An adenoma was located by scanning in 12 patients. Ten of these 12 patients underwent surgery; the scan had located the adenoma correctly in all these patients. One patient with a negative result of a scan examination subsequently had an adenoma removed at operation. Thyroid pathology interfered with the interpretation of the scan. This technique is recommended as a useful preoperative procedure for the detection of parathyroid adenomas, and its role in the rapid evaluation of hypercalcaemia seems promising. A prospective study to compare the sensitivity and specificity of this technique with computerized tomographic scanning and ultrasound is warranted.

Adenoma↗