Serotonin- and substance P-containing projections to the nucleus tractus solitarii of the rat

The objective of the present study was to determine the location of the neurons that give rise to serotonin- and substance P-containing terminals in the nucleus tractus solitarii. This was done by injecting rhodamine-filled latex microspheres into the nucleus tractus solitarii of rats to retrogradely label neuronal cell bodies and by processing sections from the brains of these animals to determine whether the labelled neurons contained serotonin or substance P immunoreactivity. Serotonin-immunoreactive neurons that projected to the nucleus tractus solitarii were found in the nucleus raphe magnus, nucleus raphe obscurus, nucleus raphe pallidus, and in the ventral medulla, lateral to the pyramidal tract. Substance P-immunoreactive neurons that projected to the nucleus tractus solitarii were found in similar areas but were proportionately less numerous in the nucleus raphe magnus and proportionately more numerous in the nucleus raphe pallidus. It is concluded that neurons in the medullary raphe nuclei, some of which presumably utilize serotonin or substance P as a neurotransmitter, could regulate autonomic function via direct projections to the nucleus tractus solitarii.

Regional peripheral and CNS hemodynamic effects of intrathecal administration of a substance P receptor agonist

Regional CNS and peripheral hemodynamic effects of the intrathecal (i.t.) administration of a substance P receptor agonist, [pGlu5,MePhe8,MeGly9]-substance P5-11 ([DiMe]-SP), were studied in anesthetized rats with the radioactive microsphere technique. It was previously shown that [DiMe]-SP caused a sympathetically mediated increase in mean arterial pressure (MAP) by an action within the spinal cord. In this study, [DiMe]-SP (5 and 33 nmol, i.t.) increased MAP. The 5 nmol dose increased resistance in cutaneous, renal, splanchnic, and adrenal vascular beds but decreased resistance, and increased blood flow in some skeletal muscle beds. Total peripheral resistance was unchanged. The 33 nmol dose increased resistance in each peripheral vascular bed analyzed and increased total peripheral resistance. Whereas each dose increased heart rate, stroke volume and cardiac output were unchanged with the 5 nmol dose and were reduced with the 33 nmol dose. Neither dose of [DiMe]-SP significantly altered regional brain or spinal cord blood flows. These data show that the i.t. administration of the SP agonist, [DiMe]-SP, increased vascular tone to most peripheral vascular beds whereas the low dose caused a vasodilation of skeletal muscle. These effects are consistent with the notion of a dose-related activation of SP receptors in the spinal cord affecting sympathetic outflow to the adrenals and to the vasculature.

Lack of effect of chronic carbamazepine on brain somatostatin in the rat

We investigated the effects of chronic carbamazepine treatment in rats on brain somatostatin. Following 12 days of carbamazepine treatment, no changes in somatostatin levels were found in any of the brain areas examined which included: amygdala, hippocampus, caudate-putamen, median eminence, arcuate nucleus, nucleus accumbens, nucleus interstitialis of the stria terminalis, nucleus periventricularis, parietal cortex, and occipital cortex. Thus, carbamazepine in low doses does not affect basal levels of brain somatostatin in the rat, in contrast to the previous reports of decreased somatostatin in the cerebrospinal fluid of affectively ill patients.

Substance P-containing medullary projections to the intermediolateral cell column: identification with retrogradely transported rhodamine-labeled latex microspheres and immunohistochemistry

Substance P (SP)-containing medullary neurons that project to the intermediolateral cell column (IML) of the rat were studied. Neurons were retrogradely labeled with rhodamine-labeled latex microspheres (RITC-M) injected into the T-3 IML, and SP-immunoreactive neurons were identified with immunocytochemistry. RITC-M labeled cells occurred in the nucleus reticularis paragigantocellular lateralis (RPgcl), adjacent and lateral to the pyramidal tract at the level of the rostral inferior olivary nucleus and extended to the mid-facial nucleus in the medulla. Cells were also labeled caudal to the RPgcl, in the nucleus reticularis ventralis, pars alpha (RVa), rostral to the RVa, in the nucleus reticularis gigantocellularis (RGc), and in the raphe nuclei. SP immunoreactivity (SP-IR) was seen in cells that were also retrogradely labeled. These double-labeled cells were observed in the RPgcl, RVa and the raphe pallidus. These data show that the IML receives SP-neuronal projections from multiple locations in the medulla. The SP-neuronal projections from the RPgcl of the ventral medulla to the IML likely represent one component of the ventral medullary region that influences cardiovascular functions.

Intrathecal administration of a substance P receptor antagonist: studies on peripheral and central nervous system hemodynamics and on specificity of action

Regional central nervous system and peripheral hemodynamic effects of the intrathecal (i.t.) administration of a substance P (SP) receptor antagonist, [D-Arg1, D-Pro2, D-Trp7,9, Leu11]-substance P ([D-Arg]-SP), were studied in anesthetized rats. It was found that [D-Arg]-SP (3.3 nmol i.t.) reduced mean arterial pressure and cardiac output due to a reduction in stroke volume. Total peripheral resistance was not altered. Whereas most vascular beds showed no alterations in vascular resistance, a renal vasoconstriction was noted. The hypotensive effect of [D-Arg]-SP was blocked by phentolamine (10 mg/kg i.v.) but not by propranolol (1 mg/kg i.v.). In the absence of changes in vascular arterial resistance due to [D-Arg]-SP, it appears that a change in venous return may contribute to the [D-Arg]-SP-induced reduction in stroke volume. These data provide evidence that a spinal cord SP system may tonically affect sympathetic neurons controlling venous, but not arterial, vasomotor tone. [D-Arg]-SP (i.t.) did not alter brain blood flow but significantly decreased blood flow in the thoracolumbar spinal cord 15 to 20 min after administration. The reduction in spinal cord flow did not appear to be responsible for the [D-Arg]-SP-induced hypotension because kainic acid (i.t.), an agent that interacts with glutamate receptors, produced similar pressor responses in the presence and absence of [D-Arg]-SP. In addition, whereas the pressor effect of low doses of a SP agonist [pGlu5, MePhe8, MeGly9]-substance P (5-11) were blocked by [D-Arg]-SP, a higher dose produced the typical pressor effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Pharmacologic characterization and autoradiographic distribution of binding sites for iodinated tachykinins in the rat central nervous system

P-type, E-type, and K-type tachykinin binding sites have been identified in the mammalian CNS. These sites may be tachykinin receptors for which the mammalian neuropeptides substance P, neuromedin K, and substance K are the preferred natural agonists, respectively. In the present investigation, we have compared the pharmacology and the autoradiographic distribution of CNS binding sites for the iodinated (125I-Bolton-Hunter reagent) tachykinins substance P, eledoisin, neuromedin K, and substance K. Iodinated eledoisin and neuromedin K exhibited an E-type binding pattern in cortical membranes. Iodinated eledoisin, neuromedin K, and substance K each labeled sites that had a similar distribution but one that was considerably different from that of sites labeled by iodinated substance P. CNS regions where there were detectable densities of binding sites for iodinated eledoisin, neuromedin K, and substance K and few or no sites for iodinated substance P included cortical layers IV-VI, mediolateral septum, supraoptic and paraventricular nuclei, interpeduncular nucleus, ventral tegmental area, and substantia nigra pars compacta. Binding sites for SP were generally more widespread in the CNS. CNS regions where there was a substantial density of binding sites for iodinated substance P and few or no sites for iodinated eledoisin, neuromedin K, and substance K included cortical layers I and II, olfactory tubercle, nucleus accumbens, caudate-putamen, globus pallidus, medial and lateral septum, endopiriform nucleus, rostral thalamus, medial and lateral preoptic nuclei, arcuate nucleus, dorsal raphe nucleus, dorsal parabrachial nucleus, parabigeminal nucleus, cerebellum, inferior olive, nucleus ambiguus, retrofacial and reticular nuclei, and spinal cord autonomic and somatic motor nuclei. In the brainstem, iodinated substance P labeled sites in both sensory and motor nuclei whereas iodinated eledoisin, neuromedin K, and substance K labeled primarily sensory nuclei. Our results are consistent with either of two alternatives: (1) that iodinated eledoisin, neuromedin K, and substance K bind to the same receptor site in the rat CNS, or (2) that they bind to multiple types of receptor sites with very similar distribution.

Studies on the cellular localization of spinal cord substance P receptors

Substance P-immunoreactivity and specific substance P binding sites are present in the spinal cord. Receptor autoradiography showed the discrete localization of substance P binding sites in both sensory and motor regions of the spinal cord and functional studies suggested an important role for substance P receptor activation in autonomic outflow, nociception, respiration and somatic motor function. In the current studies, we investigated the cellular localization of substance P binding sites in rat spinal cord using light microscopic autoradiography combined with several lesioning techniques. Unilateral injections of the suicide transport agent, ricin, into the superior cervical ganglion reduced substance P binding and cholinesterase-stained preganglionic sympathetic neurons in the intermediolateral cell column. However, unilateral electrolytic lesions of ventral medullary substance P neurons which project to the intermediolateral cell column did not alter the density of substance P binding in the intermediolateral cell column. Likewise, 6-hydroxydopamine and 5,7-dihydroxytryptamine, which destroy noradrenergic and serotonergic nerve terminals, did not reduce the substance P binding in the intermediolateral cell column. It appears, therefore, that the substance P binding sites are located postsynaptically on preganglionic sympathetic neurons rather than presynaptically on substance P-immunoreactive processes (i.e. as autoreceptors) or on monoamine nerve terminals. Unilateral injections of ricin into the phrenic nerve resulted in the unilateral destruction of phrenic motor neurons in the cervical spinal cord and caused a marked reduction in the substance P binding in the nucleus. Likewise, sciatic nerve injections of ricin caused a loss of associated motor neurons in the lateral portion of the ventral horn of the lumbar spinal cord and a reduction in the substance P binding. Sciatic nerve injections of ricin also destroyed afferent nerves of the associated dorsal root ganglia and increased the density of substance P binding in the dorsal horn. Capsaicin, which destroys small diameter primary sensory neurons, similarly increased the substance P binding in the dorsal horn. These studies show that the cellular localization of substance P binding sites can be determined by analysis of changes in substance P binding to discrete regions of spinal cord after selective lesions of specific groups of neurons. The data show the presence of substance P binding sites on preganglionic sympathetic neurons in the intermediolateral cell column and on somatic motor neurons in the ventral horn, including the phrenic motor nucleus.(ABSTRACT TRUNCATED AT 400 WORDS)

Ontogeny of substance P receptors in rat spinal cord: quantitative changes in receptor number and differential expression in specific loci

Anatomic distribution and functional studies of substance P (SP) and its binding sites show a role for the peptide in sensory (nociception), autonomic and somatic motor control. These physiologic functions show postnatal developmental changes, which, if mediated by SP, suggest that the receptors for the peptide may also undergo postnatal changes. This hypothesis was tested by using light microscopic autoradiography and membrane homogenate binding of 125I-Bolton-Hunter-SP (125I-BH-SP) to study SP binding sites in the spinal cord of rats of different ages. In cervicothoracic segments of rat spinal cord, the autoradiographs showed that specific binding of 125I-BH-SP occurred predominantly in the grey matter and varied inversely to age. In pups, up to about 15 days old, binding sites were diffusely distributed over the grey matter, and became progressively more defined in specific nuclei as the rats aged. A novel nucleus which is located in the ventrolateral ventral horn of caudal cervical segments and contained a high density of SP binding sites has been identified. High densities of SP binding sites in this nucleus and the intermediolateral cell column were visualized from the first postnatal day; however, those in the phrenic motor nucleus and in the dorsal horn were not fully expressed until after the 8th postnatal day. The age-related binding was confirmed in a membrane homogenate binding study of whole spinal cord which showed that the ratio for the concentration (cpm/mg protein) of specific binding was 106:12:4:1, for rats 11 (26 g), 38 (145 g), 90 (329 g) and 260 (553 g) days old. The ratio for the specific binding to the spinal cord (uncorrected for tissue weight) for the same groups of rats was 6:3:2:1. These data suggest that SP receptors decreased as a function of age. Furthermore, the decrease in SP receptors was not entirely due to growth of the spinal cord.

Thyrotropin-releasing hormone-immunoreactive neurons project from the ventral medulla to the intermediolateral cell column: partial coexistence with serotonin

Projections from medullary thyrotropin-releasing hormone (TRH) containing neurons to the intermediolateral cell column (IML) of the thoracic spinal cord were studied in the rat. Lesions of the ventral medullary reticular formation nuclei, nucleus paragigantocellularis lateralis and nucleus interfascicularis hypoglossi, decreased the thyrotropin-releasing hormone immunoreactivity in the IML. The ventral horn and dorsal horn contents of TRH were also reduced in rats with nucleus paragigantocellularis lateralis lesions. Coexistence of spinal cord TRH and serotonin was evaluated and quantified in 5,7-dihydroxytryptamine-treated rats. Treatment with the serotonin neurotoxin reduced the TRH content of the IML by 45% and of the ventral horn by 92%. These data show that TRH containing neurons project from the ventral medulla to IML and that approximately one-half of these TRH neurons are also serotonergic. Comparisons of the effects of the same lesions on the substance P and TRH content of the IML show that neither the origin of the SP and TRH neuronal projections to the IML, nor their coexistence with serotonin, are identical.

Changes in substance P and somatostatin in the spinal cord after traumatic spinal injury in the rat

Immunoreactive substance P (SPI) and somatostatin (SOMI) are found in spinal cord but their physiological roles remain speculative. Several classes of neuropeptides, including endogenous opioids and thyrotropin-releasing hormone (TRH), have been implicated in the pathogenesis or recovery from spinal cord injury. In the present studies, changes in SPI and SOMI were examined in the spinal cord after traumatic injury in the rat. Both peptides showed time-dependent, localized decreases at the injury site, which were statistically related to the degree of post-traumatic neurological dysfunction. Such changes differ from those of a number of other peptides after spinal injury and suggest that substance P and/or somatostatin may play a role in the secondary pathophysiological responses which follow trauma to the spinal cord.

Autoradiographic localization and characterization of spinal cord substance P binding sites: high densities in sensory, autonomic, phrenic, and Onuf's motor nuclei

The presence of the neurotransmitter or neuromodulator, substance P (SP), in the spinal cord implies that a discrete localization of SP receptors also occurs. To map the distribution of and to characterize SP binding sites in the spinal cord, light microscopic autoradiography was used. SP binding sites occurred in the dorsal horn, intermediolateral cell column (IML) and lamina X-region. In the ventral horn, the phrenic, Onuf's and sacral ventromedial motor nuclei were densely labeled. Other regions of the ventral horn were moderately labeled for SP binding sites. The localization of binding sites parallels the regional distribution of SP-containing nerve fibers in the spinal cord. A close correlation between the binding sites for SP and the presence of cholinesterase-stained neurons occurred, and suggest that the SP receptors are located on or proximal to cholinergic neurons. The density of the binding sites in the dorsal horn was highest in the sacral section, followed by the lumbar, thoracic and cervical section. In the lamina X region, however, the density was highest in the thoracic followed by the sacral, lumbar and cervical sections. The high density binding of 125I-Bolton-Hunter reagent labeled SP was inhibited, in a dose-dependent manner, by unlabeled SP. Quantification of the dose-dependent inhibition binding, using computer densitometry, showed differences in the inhibition curves for the cervical lamina X-region and the IML as compared with the other loci containing high density binding sites. The differential sensitivity of the SP receptors to unlabeled SP suggests that there are heterogeneous receptors for SP in the spinal cord, which may be relevant to the role of SP in different spinal cord functions. The binding to specific motor nuclei in the ventral horn also suggest that SP may play a role in the function of specialized striated muscles.

Cardiovascular effects of spinal cord substance P: studies with a stable receptor agonist

The role of spinal cord substance P (SP) in regulating sympathetic outflow to the cardiovascular system was assessed with the stable active analog [pGlu5,MePhE8,MeGly9]-SP(5-11) (DiME-SP). The interaction of DiME-SP with spinal cord SP receptors was evaluated initially in binding studies. Saturable, high-affinity binding of [125I]Bolton-Hunter-SP to rat spinal cord membranes was dose-dependently inhibited by DiME-SP (IC50 = 1.5 microM). Intrathecal (i.t.) injections of DiME-SP (1.0-33 nmol) in anesthetized rats produced dose-dependent increases in blood pressure and heart rate that were accompanied by increases in plasma epinephrine and norepinephrine. Intravenous injections of the ganglionic blocker pentolinium blocked the cardiovascular and plasma catecholamine responses to i.t. injections of DiME-SP. Bulbospinal sympathoexcitatory pathways originating in the ventral medulla and their mediation by SP were also assessed. As demonstrated previously, application of bicuculline, the gamma-aminobutyric acid receptor antagonist, to the ventral surface of the medulla produced sympathetic mediated increases in blood pressure and these effects were blocked by i.t. injection of the SP receptor antagonist [D-Arg1,D-Pro2,D-Trp7,9,Leu11]-SP. In this study, we studied the specificity of the SP antagonist for SP receptors by attempting to alter the actions of the SP antagonist with a SP agonist. Administration of DiME-SP (33 nmol i.t.) blocked the effects of [D-Arg1,D-Pro2,D-Trp7,9,Leu11]-SP (3.3 nmol i.t.). Specifically, the SP agonist countered the SP antagonist-mediated 1) hypotensive response and 2) inhibitory effect on bicuculline-induced sympathoexcitatory responses elicited from the ventral surface of the medulla. These data provide further evidence that SP transmits excitatory information to the cardiovascular system via spinal sympathetic pathways.

Spinal cord substance P mediates bicuculline-induced activation of cardiovascular responses from the ventral medulla

Substance P (SP) and serotonin are contained in ventral medullary projections to the intermediolateral cell column (IML) of the spinal cord, and both neurotransmitters excite sympathetic preganglionic neurons upon injection into the IML. Since gamma-aminobutyric acid (GABA) in the ventral medulla inhibits, and GABA-receptor antagonists excite sympathetic outflow to the cardiovascular system, experiments were done to determine if SP and serotonin in the spinal cord were responsible for mediating these GABAergic effects. Anesthetized rats were either given intrathecal injections of SP antagonists acutely, or pretreated with intrathecal injections of the serotonin neurotoxin, 5,7-dihydroxytryptamine. The effects of these drugs on mean arterial pressure (MAP) and heart rate (HR), as well as their ability to block the responses to topical application of GABA or the GABA antagonist, bicuculline, at the ventral medulla were assessed. Three SP antagonists (50 micrograms) decreased MAP to 2/3 baseline values, but did not change HR. They also blocked the characteristic increases in MAP and HR elicited by application of bicuculline to the ventral medulla. A lower dose (5 micrograms) of a SP antagonist also decreased MAP and blocked the bicuculline-induced increases in MAP and HR, an effect which was reversed in 1-2 h. Neonatal capsaicin treatment reduced the SP content in the dorsal horns of the thoracic spinal cord, but did not affect the cardiovascular responses to intrathecal injection of SP antagonist nor the blockade of bicuculline-induced responses. Intrathecal injection of 5,7-dihydroxytryptamine two weeks prior to the experiments resulted in 56% depletion of serotonin in the thoracic spinal cord, but did not change either basal MAP and HR, nor the responses to bicuculline and GABA applied to the ventral surface of the medulla. These data provide evidence for a role of spinal cord SP in cardiovascular regulation.

Characterization and segmental distribution of 125I-Bolton-Hunter-labeled substance P binding sites in rat spinal cord

Substance P (SP) is widely distributed in the spinal cord and has been implicated as a neurotransmitter in several spinal cord neuronal systems. To investigate SP receptors in the spinal cord, 125I-Bolton-Hunter-SP (125I-BH-SP) was used to identify and characterize spinal cord binding sites for the peptide. The binding of 125I-BH-SP had the following characteristics: high affinity; time, temperature, and membrane concentration dependent; reversible; and saturable. The IC50 of SP in whole spinal cord was 0.46 nM as compared with 0.95, 60, and 150 nM for physalaemin, eledoisin, and kassinin. Four putative antagonists of SP were less than 0.0001 times as potent as SP in inhibiting 125I-BH-SP binding. IC50s were 5, 7.5, 7.0, and 45 microM for D-Pro2, D-Trp7,9-SP; D-Pro2, D-Phe7, D-Trp9-SP; D-Arg1, D-Pro2, D-Trp7,9, Leu11-SP; and D-Pro4, D-Trp7,9,10-SP(4-11), respectively. The lumbosacral section bound 3 times more SP than the cervical and thoracic sections, although IC50 for the cervical section was 0.06 of that for the lumbosacral and thoracic sections. The data suggest more than one class of binding site for SP in the spinal cord and indicate a direct role for SP in spinal cord functions.

Corticotropin releasing factor-like immunoreactivity in sensory ganglia and capsaicin sensitive neurons of the rat central nervous system: colocalization with other neuropeptides

Immunohistochemistry and radioimmunoassay (RIA) revealed that corticotropin releasing factor (CRF)-like immunoreactivity was found to be colocalized with substance P (SP)-, somatostatin (SST)- and leu-enkephalin (LENK)-like immunoreactivity in the dorsal root- and trigeminal ganglia, the dorsal horn of the spinal cord (laminae I and II), the substantia gelatinosa, and at the lateral border of the spinal nucleus and in the tractus spinalis of the trigeminal nerve. These peptides were also located in fast blue labeled cells of the trigeminal ganglion following injection of the dye into the spinal trigeminal area. This indicates that there are possible sensory projections of these peptides into the spinal trigeminal area. Capsaicin treatment of neonatal rats resulted in a marked decrease in the density of CRF-, SP-, VIP- and CCK-containing neurons in the above mentioned hindbrain areas, whereas SST- and LENK-immunoreactivity were not changed. RIA revealed that, compared to controls, CRF, SP and VIP concentrations in these areas were decreased in rats pretreated with capsaicin, while SST levels were increased; CCK and LENK levels were unchanged. It is concluded that the primary afferent neurons of the nucleus and tractus spinalis of the trigeminal nerve are richly endowed with a number of peptides some of which are sensitive to capsaicin action. The close anatomical proximity of these peptide containing neurons suggests the possibility of a coexistance of one or more of these substances.

Suicide transport of ricin demonstrates the presence of substance P receptors on medullary somatic and autonomic motor neurons

Suicide transport of the toxic lectin, ricin, by hypoglossal and vagus neurons resulted in motor neuron loss in the associated nuclei, and reduced the binding of the 125I-Bolton-Hunter labeled substance P in the same nuclei. These data show that substance P receptors are located on the cell bodies of medullary somatic and preganglionic motor neurons of the hypoglossal and vagus nerves, and that suicide transport is a useful technique to determine the cellular localization of binding sites within a nucleus.

Capsaicin reduces substance P immunoreactivity in the lateral nucleus of the solitary tract and nodose ganglion

The effects of the neonatal administration of capsaicin on substance P (SP) immunoreactivity of the vagal sensory ganglion (nodose ganglion) and the CNS site of termination of vagal afferents (nucleus of the solitary tract-NTS) were evaluated with immunocytochemistry and radioimmunoassay. The SP content of the nodose ganglion was reduced by 58%, and a loss of immunoreactive cell bodies was found in capsaicin treated rats. Regional differences were found in the effects of capsaicin treatment on the SP immunoreactivity in the NTS. Whereas the SP in the medial portions of the nucleus was not altered, a reduction of SP immunoreactivity in the lateral portions of the nucleus was shown with immunocytochemistry and with radioimmunoassay. The data confirm that at least a portion of the vagal afferent cell bodies of the nodose ganglion and their projections to the brainstem are capsaicin sensitive. The finding that the SP in the lateral NTS is depleted by capsaicin administration may be of importance in the use of capsaicin in functional studies, particularly of the role of SP containing vagal afferents in respiration.

Bulbospinal substance P and sympathetic regulation of the cardiovascular system: a review

The neurotransmitter role of substance P in mediating sympathoexcitatory effects in the spinal cord and cardiovascular effects elicited from the ventral medulla is presented. SP neurons located in the ventral medulla project to the intermediolateral cell column (IML) of the thoracic spinal cord. Intrathecal administration of a SP analog excites sympathetic outflow to the cardiovascular system. Likewise, activation of the ventral medulla results in sympathetically mediated increases in blood pressure and heart rate which are blocked with SP antagonists. The IML contained a high density of SP binding sites through which the peptide likely exerts its sympathoexcitatory influence on the cardiovascular system.

Primate model of Parkinson's disease: alterations in multiple opioid systems in the basal ganglia

A motor disorder similar to idiopathic Parkinson's Disease develops in rhesus monkeys after several daily repeated doses of N-methyl-4-phenyl, 1,2,3,6-tetrahydropyridine (MPTP). The concentrations of peptides derived from proenkephalin A, proenkephalin B, substance P and somatostatin were measured by specific radioimmunoassays in the basal ganglia of MPTP-treated monkeys. In MPTP-treated monkeys, dynorphin B concentration was reduced in the caudate. In the putamen, the concentrations of peptides derived from both proenkephalin A and proenkephalin B were decreased. In the globus pallidus, the concentrations of all opioid peptides tend to be increased, reaching significance only for alpha-neo-endorphin. In the substantia nigra, only Met-enkephalin concentration was reduced, while other peptides derived from either proenkephalin A or proenkephalin B were not changed. Substance P and somatostatin were not changed in any brain area examined. Some of the symptoms associated with Parkinson's Disease may be related to altered activity of endogenous opiates in basal ganglia.

Substance P administration to neonatal rats increases adult sensitivity to substance P

Substance P (SP) administered subcutaneously to neonatal rats on days 1-7 after birth produced long-term physiological changes. The changes included altered pain perception and increased sialogogic response to SP, although the hypotensive response to SP was unchanged. Early exposure to the peptide therefore influenced development, particularly with respect to two systems in which SP is physiologically active. Both changes may reflect an increased sensitivity of these systems to the effects of SP.

Autoradiographic localization of substance P receptors in rat medulla: effect of vagotomy and nodose ganglionectomy

Light microscopic autoradiography of [125I]Bolton-Hunter substance P binding sites was used to study the localization and denervation-induced changes in substance P receptors in the medulla oblongata. Substance P binding sites were widely distributed. The highest density was in the rostral nucleus ambiguus, dorsal motor nucleus of the vagus, nucleus of the solitary tract, hypoglossal nucleus, spinal trigeminal nucleus and inferior olive. Moderate density was apparent in the commissural nucleus of the solitary tract, area postrema, parvocellular reticular nucleus, medial vestibular nucleus and facial nucleus. The remainder of the medullary nuclei contained few or no specific substance P binding sites. Specific binding was inhibited by the addition of unlabeled substance P (1 microM). The association of substance P binding sites with the spinal trigeminal nucleus and with several nuclei involved in autonomic function suggest a role for substance P receptor activation in nociceptive and autonomic regulation, respectively. To study the influence of afferent and efferent denervation, the substance P binding sites in the medulla of sham operated rats were compared with those of both unilateral nodose ganglionectomized and cervical vagotomized rats. Substance P binding was unilaterally reduced in the rostral nucleus ambiguus and the rostral dorsal motor nucleus of the vagus with either surgical procedure. No changes in substance P binding were detected in other medullary nuclei, including the nucleus of the solitary tract, the site of termination of afferent vagal fibers.(ABSTRACT TRUNCATED AT 250 WORDS)

The ventral surface of the medulla in the rat: pharmacologic and autoradiographic localization of GABA-induced cardiovascular effects

Experiments were done to evaluate a rat model for studying the cardiovascular effects of pharmacological manipulations of the ventral surface of the medulla. GABAergic drugs were used because of their well-characterized actions at the ventral surface of the medulla in the cat. GABA and muscimol, applied to the exposed ventral surface with filter paper pledgets, produced dose-dependent decreases in heart rate (HR) and mean arterial pressure (MAP) which were reversed with bicuculline but not with strychnine. Bicuculline alone raised HR and MAP. The GABA- or bicuculline-induced cardiovascular effects were mediated primarily by inhibition of sympathetic outflow. The most sensitive site was localized to an intermediate area on the ventral surface of the medulla, between the trapezoid body and exits of the hypoglossal nerves and just lateral to the pyramids. Topical application of [3H]GABA to the intermediate area resulted in labeling that was concentrated at the site of application, and which penetrated the parenchyma 1 mm dorsally. The heaviest labeling was found primarily in the ventral halves of the lateral paragigantocellular nuclei. No tritium was detected in peripheral blood. These data provide evidence for a neuronal system at the ventral medullary surface of the rat which influences sympathetic outflow and is modulated by GABA.

Studies on the origin and release of somatostatin-immunoreactivity in the nucleus of the solitary tract

The somatostatin content of the nucleus of the solitary tract (NTS) was regionally distributed within the nucleus and a calcium-dependent release of the neuropeptide was evoked by potassium-induced depolarization in vitro. The origin of the somatostatin in the NTS was studied with various denervation procedures. Unilateral NTS deafferentation decreased the concentration of somatostatin in the NTS. However, neither midbrain hemisection nor nodose ganglionectomy reduced the somatostatin content of the NTS. In addition, the nodose ganglion contained very low quantities of the peptide. These results suggest that (1) somatostatin may function as a neurotransmitter in the NTS and (2) the somatostatin-containing innervation of the NTS is at least in part from extrinsic neurons located in the lower brainstem and not from vagal afferent or forebrain neurons.

The effects of cysteamine and capsaicin on somatostatin and substance P in medullary nuclei

Administration of the thiol reagent, cysteamine, reduced the somatostatin content (70-80%) in each of the discrete medullary nuclei assayed without altering the substance P content of the same nuclei. In contrast, capsaicin, the putative neurotoxin for primary sensory afferent neurons had no effect on the somatostatin content of any of the medullary nuclei assayed while depleting the substance P content of the spinal trigeminal nucleus in the same animals.

Distribution and origin of bombesin, substance P and somatostatin in cat spinal cord

Bombesin (BN), substance P-(SP) and somatostatin (SRIF) were measured in individual laminae of the cervical, thoracic and lumbar (L) spinal cord of control cats, and in the L6 segment of cats receiving a spinal hemisection (L2) or deafferentation via dorsal rhizotomy at L6, 7, S1. The interlaminar distribution of BN, SP, and SRIF was remarkably similar. Highest concentrations were found in the superficial dorsal horn, and progressively less was found proceeding ventrally. Some intersegmental variations in peptide concentration within a single lamina were found. Dorsal rhizotomy caused a significant decline in BN, SP and SRIF in lamina I-III, therefore all three peptides appear to be contained in dorsal root ganglion cells. Evidence is presented for the existence of ascending BN and SP projections originating in lamina I-III and VII, for a descending SRIF pathway terminating in lamina VIII, and for an ascending BN path in lamina VIII. Dorsal root afferents to lamina VIII influence levels of BN, SP and SRIF.