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P Pilowsky

Publications and source records attributed to P Pilowsky.

At least 37 records · Page 2Linked to original sources
PubMed1995

Antisense to thyrotropin releasing hormone receptor reduces arterial blood pressure in spontaneously hypertensive rats.

We report in the present study the effect of intrathecal treatment with antisense oligonucleotides complementary to thyrotropin releasing hormone (TRH) receptor mRNA on the pressor response to intrathecal administration of TRH and on resting arterial blood pressure in Wistar-Kyoto (WKY) rats and spontaneously hypertensive rats (SHR). In 16-week-old male WKY rats, 18-base phosphodiester antisense or mismatch oligonucleotides to TRH receptor mRNA (100 micrograms per day) were injected intrathecally for 3 days. Twenty-four hours after the last injection, the magnitude of the pressor response to intrathecal TRH (10 micrograms) was significantly smaller in the antisense-treated group (n = 7) compared with mismatch-treated controls (n = 7) (change in mean arterial pressure, +20.3 +/- 3.0 versus +32.6 +/- 2.5 mm Hg, P < .01). No differences were observed in the pressor responses to injection of N-methyl-D-aspartic acid. Resting arterial blood pressure was unaffected by antisense treatment in WKY rats. In separate experiments, 16-week-old male SHR were treated with antisense (n = 7) or mismatch (n = 6) oligonucleotides for 3 days. Mean resting arterial blood pressure was significantly reduced by treatment with antisense oligonucleotides (from 157 +/- 4.8 to 119 +/- 8.8 mm Hg, P < .01), but no significant changes were observed in mismatch-treated animals. Our results suggest that the expression of TRH receptors in spinal sympathetic preganglionic neurons can be selectively reduced by intrathecal treatment with antisense oligonucleotides and that TRH projections to sympathetic preganglionic neurons play an important role in the elevation of arterial blood pressure in SHR.

Animals↗
PubMed1994

Intracellular recording from sympathetic preganglionic neurons in cat lumbar spinal cord.

Sympathetic preganglionic neurons (SPN) are responsible for the control of many autonomic targets including the heart and blood vessels. Previous intracellular studies have examined the morphology of SPN in the thoracic spinal cord, but there are no intracellular studies of SPN in the lumbar spinal cord. In this study we identified lumbar SPN using intracellular recording and dye-filling so that we could study their entire soma-dendritic tree, as well as their axons. At the same time, axonal conduction velocity was measured, and any evidence of an input in phase with phrenic nerve discharge was noted. Intracellular recordings were made from SPN in the L3 (n = 125) and T3 (n = 17) segments of the cat spinal cord. Axonal conduction velocities ranged from 0.6-8.4 m/s. In 85 lumbar SPN, the recordings lasted long enough to assess respiratory-related modulation. A respiratory-related modulation of the membrane potential was seen in 7 of these 85 neurons. All 7 respiratory-related neurons had a conduction velocity of 2.0 m/s or less, while none of the SPN with conduction velocities of more than 2.0 m/s had a respiratory rhythmicity. Histological analysis of 50 biocytin-filled SPN, including 3 with a respiratory-related modulation of their membrane potential, revealed that they occurred mostly in the principal part of the intermediolateral cell column and tended to be elongated in the rostro-caudal direction. Dendrites ramified in the intermediolateral cell column, the dorsolateral white matter and the ventral and medial gray matter. Axons arose either from cell bodies or from primary dendrites and did not bifurcate or have varicose intraspinal collaterals. This is the first report of the morphology of intracellularly filled SPN in the lumbar spinal cord.

Animals↗
PubMed1994

Close appositions between tyrosine hydroxylase immunoreactive boutons and respiratory neurons in the rat ventrolateral medulla.

The extent of the adrenergic input to respiratory neurons in the ventrolateral medulla oblongata of rats was assessed by using a combination of intracellular recording, dye filling, and immunohistochemistry. Twenty-two neurons that displayed a pronounced respiration-related modulation of their membrane potential, and could not be antidromically activated by electrical stimulation of the superior laryngeal, vagus, or facial nerves, were labelled by intracellular injection of biocytin. Three types of respiration-related neurons were labelled: small neurons located in the Bötzinger complex between 0.5 and 1.0 mm caudal to the facial nucleus; medium-sized neurons located in the ventral respiratory group 1.0 to 2.0 mm caudal to the facial nucleus; and large motoneurons located within the nucleus ambiguus 0.5 to 2.0 mm caudal to the facial nucleus. Small Bötzinger neurons [length = 22 +/- 5 microns, width = 13 +/- 3 microns, area = 222 +/- 79 microns2; (mean +/- SD, n = 5)] had membrane potentials of -15 to -27 mV during the recording period. Four of five of these cells had profuse axonal terminations between 50 microns caudal and 450 microns rostral to their somata, suggesting that they may form part of local networks responsible for generating respiratory activity. Medium-sized ventral respiratory group neurons (length = 26 +/- 5 microns, width = 18 +/- 4 microns, area = 377 +/- 141 microns2; n = 5) were found in the vicinity of the nucleus ambiguus dorsal to the lateral reticular nucleus. Three of five of these neurons had an axon that crossed the midline and travelled caudally. One axon had a collateral with varicosities close to its soma. The somata of motoneurons (length = 29 +/- 6 microns, width = 21 +/- 4 microns, area = 485 +/- 142 microns2; n = 12) were located within the nucleus ambiguus, and had axons that could be traced to exist points from the medulla. Tyrosine hydroxylase immunoreactive cells and their terminal fibres within the medulla were localised by immunocytochemistry. Small Bötzinger neurons received the largest number of close appositions from tyrosine hydroxylase immunoreactive boutons (13 +/- 2 appositions/neuron; n = 5). Medium-sized ventral respiratory group neurons received fewer appositions (8 +/- 4 appositions/neuron; n = 5). Most motoneurons (n = 10) received few appositions from tyrosine hydroxylase immunoreactive boutons, while two received none. The average number was 3 +/- 3 appositions/neuron (n = 12).(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1994

Projections from inspiratory neurons of the ventral respiratory group to the subretrofacial nucleus of the cat.

Arterial blood pressure and the activity of many sympathetic nerves are known to be affected by changes in central respiratory activity. The central neurons responsible for this respiratory modulation are unknown. In the present study we have labelled inspiratory neurons (n = 24) in the rostral ventral respiratory group and Bötzinger complex in the medulla oblongata of the cat using intracellular injection of biocytin. The filled neurons were examined to see if they had axonal projections to the subretrofacial nucleus, an important brainstem nucleus in the tonic and reflex control of blood pressure. The subretrofacial nucleus was identified histologically as a cluster of neurons in the rostral ventrolateral medulla, some of which are tyrosine hydroxylase immunoreactive. Varicose axons arising from labelled inspiratory neurons were mostly found dorsal to this cluster, within the area corresponding to the Bötzinger complex. A small number of axon varicosities were seen in the subretrofacial nucleus. The results suggest that a part of the respiratory modulation of sympathetic nerve activity may be due to a direct synaptic input from inspiratory neurons of the ventral respiratory group to neurons of the subretrofacial nucleus.

Animals↗
PubMed1994

Central neurons and neurotransmitters in the control of blood pressure.

1. In this paper we review recent work from our laboratory on two major pathways important in the central control of blood pressure. 2. We report experiments on the sympatho-excitatory bulbospinal pathway from the rostral ventral medulla. Here we focus particularly on the role of excitatory amino acids. 3. We review studies on the short inhibitory or depressor pathway ascending from the caudal to the rostral ventral medulla, which is thought to use gamma-aminobutyric acid (GABA) as its neurotransmitter. We report on experiments with the immediate early gene, c-fos, demonstrating that its expression in the bulbospinal pressor neurons is increased by stimuli that activate these nerves, and that this expression can be blocked in vivo by treatment with an antisense oligonucleotide. We also show that basal and stimulated expression of the c-fos gene is important in the central control of blood pressure.

Animals↗
PubMed1994

c-fos antisense in rostral ventral medulla reduces arterial blood pressure.

The effect of blocking the expression of c-fos in the rostral ventral medulla (RVM) on the control of arterial blood pressure was determined. In six male Wistar-Kyoto rats (WKY), unilateral injection of an antisense oligonucleotide to c-fos mRNA suppressed the expression of Fos-like immunoreactivity in neurons in the RVM in response to inhibition of depressor neurons in the caudal ventrolateral medulla (CVLM). Under pentobarbital anesthesia the mean arterial pressure of rats injected with antisense oligonucleotide (n = 10) bilaterally into RVM was significantly reduced after 6 h compared with sense-treated controls (n = 9) (76.5 +/- 3.7 vs. 92.4 +/- 3.5 mmHg; P < 0.05). Furthermore, the pressor response to bilateral injection of muscimol into CVLM was significantly smaller in rats injected with antisense oligonucleotide 6 h earlier (n = 6) compared with sense-treated controls (n = 6) (changes in mean arterial pressure, +40.3 +/- 3.6 vs. +68.7 +/- 4.8 mmHg, P < 0.005). These studies demonstrate that expression of c-fos in the RVM can be blocked in vivo by treatment with an antisense oligonucleotide, and that basal and stimulated expression of the c-fos gene is important in the central control of arterial blood pressure.

Animals↗
PubMed1993

The tungstate-stabilized tetramethylbenzidine reaction for light and electron microscopic immunocytochemistry and for revealing biocytin-filled neurons.

A peroxidase reaction product that can be easily distinguished from standard diaminobenzidine (DAB) reaction products is needed for pre-embedding electron microscopic double-antibody labelling studies. Benzidine dihydrochloride (BDHC) and gold-substituted silver peroxidase reactions are unsatisfactory for double labelling because they lack sensitivity and reliability and/or compromise ultrastructure. We show here that light and electron microscopic immunocytochemistry can be done with a modification of the tungstate-stabilized tetramethylbenzidine (TMB) reaction (Weinberg and Van Eyck 1991) which yields a crystalline reaction product. With this method, we have obtained excellent immunolabelling for a variety of antigens, including tyrosine hydroxylase, enkephalin, serotonin, Fos protein and retrogradely transported cholera toxin B subunit (CTB). The TMB-tungstate reaction is useful for ultrastructural double labelling because the crystals contrast well with the amorphous product of diaminobenzidine reactions. The TMB-tungstate reaction is more sensitive and reliable for immunocytochemistry than the benzidine dihydrochloride reaction and gives better ultrastructure than the gold-substituted silver peroxidase reaction. We also show that neurons filled with biocytin by intracellular injection can be visualized with TMB-tungstate for either light (LM) or electron (EM) microscopy.

Animals↗
PubMed1992

Cheap thrills.

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Bedding and Linens↗
PubMed1992

Sympathetic preganglionic neurons projecting to the adrenal medulla and aorticorenal ganglion in the rabbit.

The distribution of sympathetic preganglionic neurons (SPN) projecting to the adrenal medulla and the aorticorenal ganglion in the rabbit was studied using a dual retrograde transport technique. The B subunit of cholera toxin (CTB) was injected into the left adrenal medulla and wheatgerm agglutinin-apo-horseradish peroxidase-7 nm gold (WGA-apo-HRP-gold) was injected into the left aorticorenal ganglion. Retrogradely transported CTB was detected by immunohistochemistry, while gold particles were detected by silver intensification. SPN projecting to the adrenal medulla were observed in segments T2-L2 of the spinal cord in 5 rabbits, with the majority of cells within segments T6-T11 (79%). SPN projecting to the aorticorenal ganglion were seen in segments T2-L1 of the spinal cord in 5 rabbits, with the greatest number of the cells within T6-T11 (81%). Only a small number of doubly labelled cells (1%) were found in two rabbits. The results suggest that despite their similar segmental distribution SPN projecting to the adrenal medulla or the aorticorenal ganglion belong to separate populations and few, if any, individual SPN have axonal projections to both locations.

Adrenal Medulla↗
PubMed1992

Substance P immunoreactive boutons form synapses with feline sympathetic preganglionic neurons.

In this study, the relationship between substance P-immunoreactive boutons and antidromically activated sympathetic preganglionic neurons was examined by light and electron microscopy. Sympathetic preganglionic neurons in the T2-T4 spinal segments of the cat were identified by intracellular recording and antidromic activation from the corresponding white ramus. Neurons were filled with lucifer yellow and then stained to reveal, simultaneously, substance P and lucifer yellow immunoreactivity. All of the neurons examined with the light microscope (n = 13) received appositions from substance P-immunoreactive boutons. Appositions were found on all parts of the neuron, including the somata, dendrites, and axon initial segment. In most cases (11/13) few close appositions were seen; however, two neurons received large numbers of appositions from substance P-immunoreactive boutons. On one neuron, 16 substance P-immunoreactive varicosities that were identified as being closely apposed at the light microscope level were serially sectioned and examined with the electron microscope. Of these 16 varicosities, eight either directly contacted the neuron or formed morphologically identifiable synapses. The remaining eight varicosities were separated from the neuron by thin glial processes. Two other sympathetic preganglionic neurons that were examined ultrastructurally also received substance P-immunoreactive synapses and close contacts. These findings suggest that substance P-containing nerve fibres could affect all sympathetic preganglionic neurons but are likely to be important in regulating the activity of only a small proportion of these neurons.

Animals↗
PubMed1992

Sympathetic preganglionic neurons in rabbit spinal cord that project to the stellate or the superior cervical ganglion.

The segmental distribution of sympathetic preganglionic neurons in the rabbit spinal cord that project to the stellate or the superior cervical ganglion was determined using retrograde tracing with cholera toxin B subunit from the stellate ganglion and wheat germ agglutinin-apo-horseradish peroxidase-gold from the superior cervical ganglion. Sympathetic preganglionic neurons that projected to the stellate ganglion were located in spinal segments T1 to T10. Sympathetic preganglionic neurons projecting to the superior cervical ganglion were found in segments T1 to T8. Both types of neuron had somata that were elongated in the rostrocaudal direction, and dendrites that were mainly confined to the intermediolateral cell column. Almost 95% of the neurons supplying the superior cervical ganglion had axons that passed through the stellate ganglion.

Animals↗
PubMed1992

Ultrastructural evidence for GABA-mediated disinhibitory circuits in the spinal cord of the cat.

The synaptic relationships between gamma-aminobutyric acid (GABA)-immunoreactive and enkephalin-immunoreactive profiles in the cat spinal cord were examined using combined pre-embedding immunoperoxidase and post-embedding immunogold electron microscopic immunocytochemistry. Although colchicine was not used, enkephalin-immunoreactive somata and dendrites were detected in regions associated with nociceptive transmission, including laminae I, II, V and X. In each of these laminae, many GABA-immunoreactive terminals were found presynaptic to enkephalin-immunoreactive cell bodies and dendrites. We propose that disinhibition of opioid-containing neurons may be a common feature of pain-related circuits in the cat spinal cord.

Animals↗
PubMed1992

Kainic acid injection in NTS evokes hypertension and c-fos expression in spinal cord.

Kainic acid injected into rat nucleus tractus solitarius (NTS) caused a slowly developing hypertension, with a 2-fold increase in Fos-immunoreactive (Fos-IR) nuclei in the area of the presympathetic bulbospinal neurons in the rostral ventrolateral medulla (RVLM) and a widespread activation of sympathetic preganglionic neurons (SPN) in the spinal cord, particularly in the mid to lower thoracic cord. The highest segmental concentration of Fos-IR SPN was in T8, with Fos-IR nuclei increased 12-fold compared with the vehicle injected group. More than 60% of retrogradely labelled sympathoadrenal neurons in T8 were Fos-IR after kainic acid injection, consistent with the 60-fold increases in plasma adrenaline levels observed in these rats.

Animals↗
PubMed1992

Axonal projections from respiratory centres towards the rostral ventrolateral medulla in the rat.

1. Efferent pathways from brainstem respiratory centres towards bulbospinal tyrosine hydroxylase immunoreactive neurons were identified in the rat using a combination of electrophysiology, retrograde and anterograde tract-tracing, and immunohistochemistry. 2. Varicose axons originating from respiratory centres were found in close apposition to bulbospinal tyrosine hydroxylase immunoreactive neurons in the ventrolateral medulla. 3. These findings support the idea that respiratory rhythms in sympathetic nerves may be due to a synaptic connection between brainstem respiratory neurons and bulbospinal tyrosine hydroxylase immunoreactive neurons of the C1 cell group.

Animals↗
PubMed1992

Amino acid neurotransmitters in hypertension.

There is compelling evidence for the participation of excitatory and inhibitory amino acids in the neural regulation of blood pressure in the normotensive rat. This is most clearly evident in the neural pathways which form the baroreceptor reflex arc. Excitatory amino acids are contained in baroreceptor afferents, neurons in the nucleus tractus solitarius (NTS) and neurons in the rostral ventrolateral medulla (RVLM). Inhibitory neurons in the caudal ventrolateral medulla (CVLM) contain gamma-aminobutyric acid. Electrophysiological and pharmacological evidence indicates that amino acid neurotransmitters are critically important to the normal function of these integrative sites in the baroreceptor reflex. Spontaneously hypertensive rats (SHR) differ from Wistar Kyoto (WKY) controls in their responses to stimulation, inhibition or lesions of neurons in the baroreceptor arc. One week after baroreceptor denervation, blood pressure is elevated in WKY but not in SHR. Stimulation of the CVLM results in a greater fall in pressure in SHR than WKY, whereas injection of tetrodotoxin into the CVLM results in a smaller increase in pressure in SHR. Blockade of glutamate receptors in the spinal cord attenuates the response to stimulation of the RVLM in both SHR and WKY, but reduces resting blood pressure in SHR only. These experiments suggest that altered activity in amino acid pathways contributes to the pathogenesis of hypertension in SHR.

Amino Acids↗
PubMed1991

Glutamate in spinally projecting neurons of the rostral ventral medulla.

Phosphate activated glutaminase (PAG), an enzyme of glutamate synthesis, was localized by immunohistochemistry in all PNMT-immunoreactive and all serotonin-immunoreactive neurons in the rostral ventral medulla of the rat. Between 71 and 83% of bulbospinal neurons localised in the rostral ventral medulla projecting to the intermediolateral cell column in the upper thoracic spinal cord contained PAG immunoreactivity. Of these bulbospinal PAG-immunoreactive neurons 17-27% contained PNMT immunoreactivity and 9-16% contained serotonin immunoreactivity. Other bulbospinal PAG-immunoreactive neurons (60-70%) contained neither PNMT- nor serotonin immunoreactivity. The results provide anatomical evidence suggestive of a glutamatergic input to the sympathetic preganglionic neurons of the spinal cord arising from different populations of neurons located in the rostral ventral medulla.

Animals↗