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H Klemfuss

Publications and source records attributed to H Klemfuss.

24 records · Page 2Linked to original sources
PubMed1987

Do antidromic latency jumps indicate axonal branching in nigrostriatal and hypothalamo-neurohypophysial neurons?

Neurons in many brain regions exhibit discontinuous decreases in antidromic latency with small increases in stimulating current. We used an electrophysiological test requiring a single stimulating electrode to determine whether these 'latency jumps' are due to shifts in the site of spike initiation to the same or different axon branches. Latency jumps in response to stimulation of the striatal terminal fields of substantia nigra, pars compacta neurons represent spike initiation on different branches while those seen in paraventricular neurons with pituitary stalk stimulation usually reflect a change in site on a single branch.

Animals↗
PubMed1986

Hypothalamic catecholamine metabolism is increased by acute water imbalance.

Disruption of water balance alters the metabolism of norepinephrine (NE) and dopamine (DA) in specific regions of the hypothalamus in the rat. Rats received one of the following treatments: hypertonic saline injection (1 M NaCl, 15 ml/kg), polyethylene glycol (40% polyethylene glycol in normal saline, 15 ml/kg), intragastric water load (10 ml), or ligation of the inferior vena cava. Catecholamine metabolism was determined by measuring the concentrations of NE and DA in the hypothalamus after catecholamine synthesis inhibition by alpha-methyl-p-tyrosine methyl-ester hydrochloride (200 mg/kg). No two treatments affected catecholamine metabolism in the same region of the hypothalamus. Intracellular dehydration by hypertonic saline increased NE metabolism in the paraventricular nucleus. Caval ligation, which stimulates the renal renin-angiotensin system, specifically increased NE metabolism in the preoptic area. Water loading increased the metabolism of NE and DA in the dorsomedial/ventromedial region. The effectiveness of the various treatments in increasing catecholamine metabolism was independent of the magnitude of their effects on blood pressure or water intake. The results suggest that there are multiple noradrenergic systems in the hypothalamus which respond to different types of water balance disruption.

Animals↗
PubMed1986

Autonomic mechanisms for morphine and amphetamine mydriasis in the rat.

Morphine sulfate and amphetamine sulfate dilate the pupil of the conscious, unrestrained rat. To examine the mechanisms underlying amphetamine and morphine mydriasis, the pupil diameter of freely moving rats was measured from photographs taken before and after these drugs were administered s.c., i.c.v. or by instillation into the eye. Some rats received monoamine antagonists, sympathetic denervation, or adrenalectomy before drug administration. The results indicate that both amphetamine and morphine mydriasis are primarily due to centrally mediated inhibition of parasympathetic outflow, although for both drugs there may be a sympathetic component. Pharmacological evidence indicates that the mydriatic effect of a low dose of amphetamine is mediated by actions on both alpha-1 and alpha-2 adrenergic receptors, whereas only alpha-2 adrenergic receptors are involved in morphine mydriasis.

Adrenalectomy↗
PubMed1985

Water deprivation increases anterior hypothalamic norepinephrine metabolism in the rat.

Rats were limited to 10 min of access to water per day. After 1 week, concentrations and rate of metabolism of dopamine, norepinephrine and epinephrine were determined in hypothalamic and limbic areas associated with regulation of water homeostasis. Chronic water deprivation caused hypovolemia, hypotension and ingestion of a large volume of water when water became available. Norepinephrine metabolism was consistently increased in samples containing the anterior hypothalamic nucleus, but no other catecholamine in any other brain area was significantly affected by the deprivation schedule. We conclude that the anterior hypothalamic nucleus is involved in the response to chronic disruption of water balance in the rat.

Animals↗
PubMed1979

Morphine-induced mydriasis and fluctuation in the rat: time and dose relationships.

The purpose of this investigation was to establish complete dose- and time-response relationships of morphine action on the rat pupil using serial observations. Adult male, albino rats of the Sprague-Dawley strain were used. Pupil size was measured by a series of photographs taken every 60 sec for at least 90 min under dim red illumination. The pupil began to dilate within 20 min after s.c. administration of doses of morphine sulfate as low as 1 mg/kg. The dose-related mydriasis reached a maximum with a dose of 32 mg/kg at 35 to 50 min after injection and lasted for 3 to 4 hr. The mydriasis was characterized by a rapid and marked fluctuation which was also dose-related and reached a peak with 32 mg/kg of morphine sulfate. Naloxone HCl (1 mg/kg) rapidly reversed both the mydriasis and the oscillation, thereby implicating an opiate receptor-mediated mechanism. In addition to providing a convenient measure of narcotic actions, the pupil may offer a particularly useful means for studying opiate receptor mechanisms since it is one of the few cases where, in many species, the anatomical pathways and neurochemical innervations are known.

Animals↗