Medulla-pons Of Rats Research Articles

Modification by oxazepam of the diurnal variations in brain 125I-melatonin binding sites in sham-operated and pinealectomized rats.

Sham-operated and pinealectomized male rats were maintained at 14 h light:10 h dark cycles (lights-on 5.00 h) and injected daily, for 14 days, with oxazepam or vehicle. 125I-melatonin binding was recorded in synaptosomes prepared at 10.00, 18.00, and 24.00 h from the hypothalamus, hippocampus and medulla-pons of the rats. In the sham-operated, vehicle treated rats, specific 125I-melatonin binding in all brain areas studied was higher at 18.00 h, whereas in the oxazepam-treated animals, binding was higher at 24.00 h than at the other times tested. In the pinealectomized, vehicle-treated rats, the binding recorded at 18.00 h in all three brain areas, was lower than at the other times of day tested. Oxazepam treatment decreased 125I-melatonin binding at 24.00 h in the hippocampus and medulla-pons of the pinealectomized rats and did not significantly affect the binding in the hypothalamus. These results indicate the ability of oxazepam, pinealectomy and their combination, to manipulate the diurnal variations in 125I-melatonin binding sites in the rat brain.

Release of high molecular weight forms of met 5-enkephalin-arg 6-gly 7-leu 8 from rat brain

The release of various molecular weight forms of met 5-enk-arg 6-gly 7-leu 8 (MERGL) from slices prepared from rat medulla-pons and hypothalamus was studied. The release of MERGL-IR from both medulla-pons and hypothalamic slices was elevated four- to ten-fold in response to potassium depolarization. Gel filtration chromatography revealed that in both tissues, substantial quantities of 8 to 10 kilodalton MERGL-IR peptide(s), as well as MERGL itself, were released in response to stimulation with 50 mM K +.

Independent origin and modulation of vasopressin as compared to dynorphin and α-neo-endorphin in the medulla-pons of the rat

Bilateral, radiofrequency destruction of the hypothalamic paraventricular nucleus resulted in a pronounced depression in levels of immunoreactive (ir-) vasopressin (VP) in the medulla-pons of rats. The contents of ir-dynorphin 1–17 (DYN), ir-DYN 1–8 and ir-α-neo-endorphin (α-NE) therein were not, in contrast, affected. Exposure of naive rats to acute foot-shock stress was associated with an elevation in levels of ir-VP in the medulla-pons whereas those of ir-DYN, ir-DYN 1–8 and ir-α-NE were not significantly altered. The data indicate that the paraventricular nucleus is a major source of ir-VP but not of ir-DYN, ir-DYN 1–8 or ir-α-NE in the medulla-pons, and that these pools of ir-VP, in contrast to those of ir-DYN, ir-DYN 1–8 and ir-α-NE, are involved in the response to stress. It is concluded that ir-DYN, ir-DYN 1–8 and ir-α-NE exists in (a) neuronal network(s) independent of that of ir-VP in the medulla-pons of the rat.

Acetylarsenocholine: a cholinergic agonist.

The pharmacological properties of acetylarsenocholine, an arsenic analogue of acetylcholine, were investigated. Acetylarsenocholine behaved as a cholinergic ligand both in the central and peripheral nervous system. It bound to nicotinic receptors in rat medulla-pons with a KD of 15 microM and to muscarinic receptors in rat cerebral cortex with a KD of 10 microM. It behaved also as an agonist at presynaptic muscarinic receptors in guinea pig ileum myenteric plexus preparation. Arsenocholine is an alternative substrate for choline acetyltransferase and acetylarsenocholine is an alternative substrate for acetylcholinesterase.