Study of the compressibility of chewing gum and its applicability as an oral drug delivery system.

Medicated chewing gum tablets were prepared and evaluated as an oral drug delivery system. The morphology and surface free energy of the components were characterized, and the tablets were prepared by direct compression with an instrumented eccentric tableting machine. The compressibility, the porosity and the texture of the tablets were investigated and the dissolution of the active pharmaceutical ingredient (caffeine) from them was tested with a specially-developed method. Cafosa gum base is a co-processed product which is compressible. Because of the sticking of the tablets to the punches and the high friction that arises during ejection from the die, the use of lubricants and suitable (e.g. Teflon-coated) punches is necessary on a production scale. For this purpose, magnesium stearate with high specific surface area was applied. The release of caffeine in response to the mechanical effect applied proved to be rapid and quantitative and the profile closely obeyed the Korsmeyer-Peppas equation, which is valid in the case of matrix systems. Medicated chewing gum tablets can be used as matrix tablets for oral pharmaceutical administration.

Formulation study of directly compressible chewable polymers containing ascorbic acid.

The topic of this article is the compression physics of different gum bases which can be used to prepare chewing gum tablets by direct compression. Three different gum bases, Pharmagum(®) C, M and S, were tested alone and in different combinations. The preparations were compressed with a Korsch EK0 eccentric tableting machine at compression forces of 5, 7.5, 10, 12.5 and 15 kN. The compression and breaking processes and the physical parameters of the tablets were investigated. The results revealed that increase of the compression force did not significantly change the studied parameters of the tablets.

Distribution of oxytocin-immunoreactive neuronal elements in the rat spinal cord.

We investigated the distribution of oxytocin in rat spinal cord using immunocytochemistry and radioimmunoassay (RIA). Each segment of the spinal cord from cervical to coccygeal contained oxytocin-immunoreactive fibers. The Rexed laminae I and II of the dorsal horn showed moderate to intense immunoreactivity. A dense network was found around the central canal where some fibers apposed the ependyma. The autonomic centers of the spinal cord at the thoracolumbar and sacral segments were heavily innervated. Few fibers were found around the motoneurons. In the white matter, the immunoreactivity was localized mainly in the dorsal part of the lateral funiculus, in the pars funicularis of the nucleus intermediolateralis and in a longitudinal network of the lateral funiculus below the spinal cord surface. Some fibers from this network entered the pia mater. RIA measurements revealed that the cervical spinal cord had lower oxytocin content than that found in either the thoracic, lumbar, sacral or coccygeal region. Our results show that the distribution of oxytocin-immunoreactive fibers in the spinal cord correlates with anatomic locations related to nociceptive, autonomic and motor functions. We assume that oxytocin-containing axons play a role in secreting oxytocin directly into the liquor space of the spinal cord.

Specific radioimmunoassay of oxytocin in rat plasma.

Sensitive, specific and reproducible radioimmunoassay (RIA) was developed for the measurement of oxytocin (OXT) in rat blood plasma after various extraction methods. The assay is based on an antiserum raised against OXT in rabbit. The sensitivity, affinity constant, and cross-reactivity of the antiserum were determined. The 125I-labelled OXT for RIA was produced by chloramine-T method and purified with high pressure liquid chromatography (HPLC). Two extraction procedures were employed: 1. adsorption to an artificial silicate, Lichroprep Si 60 (Merck); 2. immunoextraction of the hormone applying a magnetic bearer covered with purified antibodies against OXT. The specificity of the extraction methods was characterized in comparative HPLC/RIA studies of specimens extracted from blood plasma in different ways. The basal level of the peptide measured after the extraction with thermally activated Lichroprep Si 60 or after the immunoextraction method was found to be 9.6 +/- 2.3 pg/ml (mean +/- S.E.) and 15.3 +/- 0.9 pg/ml (mean +/- S.E.), respectively. Various well known factors (ether exposure, hyperosmotic stress and suckling) appeared to be potent peripheral stimuli of OXT release, and thus indicated the suitability of the RIA method for the measurement of OXT in blood plasma.

Chromatographically identified oxytocin in the human peripheral nervous system.

Immunoreactive oxytocin (OXT) detected in extracts of human coeliac ganglia and nn. vagi was characterized by high-performance liquid chromatography (HPLC). HPLC/RIA examinations demonstrated that a major part of the immunoreactive material in both investigated areas co-eluted with a reference synthetic OXT, but in the extracts of coeliac ganglia a second immunoreactive peak was also observed.

Central effects of antiserum against human atrial natriuretic polypeptide on water and electrolyte metabolism and plasma arginine-8-vasopressin level in conscious rats.

Although synthetic atrial natriuretic polypeptide (ANP) is known to influence the water and electrolyte metabolism and arginine-8-vasopressin (AVP) secretion, the physiological role of endogenous ANP in the rat brain is still unclear. Accordingly, an investigation was made of the effects of intracerebroventricular (icv) administration of human h-ANP antiserum, which can neutralize endogenous ANP, on the water intake, urine output, urinary excretion of potassium and sodium, and plasma AVP level in normally hydrated rats. Apart from the water intake, all the parameters were also determined in 48-h water-deprived rats after h-ANP antiserum treatment. The icv administration of the h-ANP antiserum significantly increased the spontaneous water intake, urine output and urinary potassium excretion in rats given water ad libitum. These effects developed by 24 h after icv treatment. The h-ANP antiserum had no effect on the urine volume in 48-h water-deprived rats, suggesting a primary effect of endogenous ANP in the brain on the spontaneous water intake in rats given water ad libitum. These results suggest that ANP may have a physiologically important role in the central regulation of the water and electrolyte metabolism. The h-ANP antiserum did not alter the basal and dehydration-induced AVP release. This raises the possibility that the endogenous ANP in the brain may not participate in the control of AVP secretion.

Characterization of oxytocin immunoreactivity in human sympathetic paravertebral ganglia.

Immunoreactive oxytocin (IR-OXT) detected in extracts of human lumbar sympathetic paravertebral ganglia was characterized by high-performance liquid chromatography (HPLC). The immunoreactive substance was found to elute at the same position as the reference preparation of oxytocin (OXT). The results revealed the presence of chromatographically identified OXT in human sympathetic ganglia.

Acute effects of peripheral histamine administration on arginine-8-vasopressin and oxytocin levels in rat spinal cord.

The effects of a single injection of 20 mg/kg histamine on the immunoreactive arginine-8-vasopressin (AVP) and oxytocin (OXT) levels in the rat spinal cord were studied after peripheral (intraperitoneal) administration. Histamine induced a 60% elevation in the AVP content of the spinal cord, whereas the spinal level of OXT decreased by 36%. The findings suggest that peripheral histamine differentially affects the AVP and OXT levels in the spinal cord.

The effect of atrial natriuretic factor on arginine-8-vasopressin and oxytocin levels in various brain regions and plasma.

The effect of intracerebroventricular (i.c.v.) treatment of rat atrial natriuretic factor III (ANF III; 0.5 microgram) was measured on the arginine-8-vasopressin (AVP) and oxytocin (OXT) contents of rat hypothalamic and limbic brain areas as well as those in the plasma. The hormone concentrations were determined by radioimmunoassay (RIA). The administration of ANF III in conscious euhydrated rats resulted in a significant reduction of both AVP and OXT contents in the hippocampus. Ether anesthesia interfered with the effect of ANF III, since in anesthetized rats ANF III reduced the levels of AVP and OXT in the septal regions, too. ANF III had no effect on the basal plasma AVP and OXT concentrations, however, the peptide inhibited the plasma AVP and OXT elevation induced by hyperosmosis (intraperitoneal injection of 2.5% NaCl). The results suggest that ANF III may be important in the control of the activity of both the peripheral (hypothalamo-neurohypophyseal) and the central (brain) AVP-ergic and OXT-ergic systems.

Hyponatremia and increased secretion of vasopressin induced by vincristine administration in rat.

Administration of vincristine resulted in a hyponatremic state and concurrent elevation of the plasma immunoreactive arginine8-vasopressin (IR-AVP) level in rats. Development of the vincristine-induced hyponatremia and hypoosmolality was accompanied by a loss in weight, a decreased water intake and a large reduction in the daily urine sodium excretion. The cause of the sodium loss is thought to be the diarrhea observed during vincristine treatment. Hematocrit and serum urea nitrogen levels were increased. It is concluded that the condition differs from the syndrome of inappropriate secretion of antidiuretic hormone (SIADH): the increase in plasma IR-AVP concentration may be associated with dehydration due to vincristine toxicity.

Presence of chromatographically identified oxytocin in human sensory ganglia.

Oxytocin-like immunoreactivity (IR-OXT) was detected in extracts of human spinal L5 and Gasserian ganglia by a radioimmunoassay (RIA) specific to oxytocin (OXT) and was identified by high-performance liquid chromatography (HPLC). One of the two immunoreactive peaks obtained on HPLC was found to elute at the same position as the OXT standard. The results reveal the presence of chromatographically identified OXT immunoreactivity in human sensory ganglia.

Immunoelectronhistochemical evidence for innervation of brain microvessels by vasopressin-immunoreactive neurons in the rat.

Peroxidase-antiperoxidase (PAP) immunocytochemistry at the electron microscopic level was used to describe the fine structural characteristics of vascular connections between vasopressin (VP)-immunoreactive neuronal elements and cerebral microvessels in the rat. In the majority of connections, somata or neural processes (mainly dendrites) showing VP-like immunoreactivity were separated from the vessel wall by thin glial processes. In addition, some VP-positive elements could establish direct contacts with the basal lamina of the endothelium or of a pericyte associated with the capillary bed. The findings provide immunocytochemical evidence that the vasopressinergic neuronal elements can directly innervate microvessels in the brain and thereby participate in regulating the local permeability of and the flow through the cerebral microvessels.

Perineural microtubule inhibitors induce degenerative atrophy of central nociceptive terminals in the Rolando substance.

Short-term perineural application of a microtubule inhibitor around a peripheral nerve induces degenerative atrophy of primary central nociceptive terminals in the Rolando substance. Consequences of the local microtubule inhibitor treatment are identical, both at light- and electron microscopic levels, with those that follow transection of a peripheral nerve. Degenerative atrophy in the Rolando substance is due to arrested axoplasmic transport in, and not to Wallerian degeneration of, the peripheral axons since (1) locally applied vinblastine and vincristone do not induce peripheral degeneration at all and (2) even though local colchicine treatment may cause Wallerian degeneration of thick myelinated axons, thin Adelta and C fibers do not undergo degeneration after colchicine treatment. The intriguing possibility to use this approach in the treatment of intractable pain is discussed.