SEARCH · PubMed Health

Results for “Neural Pathways”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,351 records · Page 75Linked to original sources

PubMed1991

Pharmacological approaches to appetite suppression.

It is relatively easy to demonstrate drug-induced anorexia in animals, but the significance of-such suppression of eating is often doubtful. Of the many agents shown to be 'active' in animals, only a very few are genuine appetite suppressants with clinical potential. Drugs that increase central 5-HT levels, or that activate peripherally acting peptides, are currently among the most promising candidates. John Blundell advocates a systems approach to the study of appetite control. Drug-induced changes in feeding should be interpreted according to a system which involves behaviour, peripheral physiology and brain neural pathways. Appetite involves more than alterations of food intake; the concept should take into account changes in hunger, food preferences, responses to taste and changes in macronutrient preferences.

Animals↗

PubMed1992

Neurobiology of opiate abuse.

Opiates interact with cell surface receptors on neurons involved in the transmission of information along neural pathways that are related to behaviours essential for the life of the self and of the species. Opiates are provided with powerful and multifaceted rewarding properties that are fundamental for the acquisition, maintenance and relapse of opiate addiction. Gaetano Di Chiara and Alan North argue that both dopaminergic and non-dopaminergic systems are involved in opiate reward, and that opiate addiction results from adaptive and learning processes involving both positive reinforcing mechanisms related to the rewarding properties of opiates and negative reinforcing mechanisms related to the aversive properties of withdrawal in dependent subjects.

Animals↗

PubMed1996

A neurological dissociation between shape from shading and shape from edges.

We studied the ability of a neurological patient, who has deficits in various aspects of form perception, to perform region segregation tasks requiring discriminations based on several image properties that are related to the three-dimensional structure of objects. The patient could discriminate the apparent three-dimensional structure and orientation of shapes defined by shading gradients, but could not make such discriminations for shapes in which edges were depicted as lines or as luminance discontinuities. These results suggest that the neural pathways that compute shape from shading gradients may be independent of those that compute shape based on edges, and, based on the patient's pattern of brain damage, they also indicate a relatively early functional separation in the requisite inputs.

Adult↗

PubMed1996

The effects of lesions in the mesencephalic raphe systems on male rat sexual behavior and locomotor activity.

Lesions were produced in the median and the dorsal raphe nuclei of the rat, and the effects of these injuries on various behaviors were studied. The median raphe lesions had facilitatory effects on the male rat sexual behavior, as evidenced by a decrease in the number of intromissions prior to ejaculation, as well as shortening of the ejaculation latency and the postejaculatory interval. No effects were seen on the masculine sexual behavior after lesions in the dorsal raphe nucleus. The median raphe lesions drastically increased the locomotory activity whereas the dorsal raphe lesions did not. Treatment with FG5893, a 5-HT1A agonist/5-HT2A receptor antagonist, increased the locomotor activity of the dorsal-raphe-lesioned rats but did not affect the median-raphe-lesioned animals. These results suggest that the dorsal and the median raphe nuclei play different roles in the neural regulation of the sexual behavior and locomotor activity of the male rat. The median raphe nucleus appears to exert a modulatory influence upon these behaviors, which probably is mediated by serotonergic neural pathways.

Animals↗

PubMed1996

Role of the hypothalamic paraventricular nucleus in 5-HT1A, 5-HT2A and 5-HT2C receptor-mediated oxytocin, prolactin and ACTH/corticosterone responses.

To test the hypothesis that the mechanisms of 5-HT1 and 5-HT2 receptor-mediated hormonal responses are different, we compared the effects of hypothalamic paraventricular nucleus (PVN) lesions on the ACTH/corticosterone, prolactin and oxytocin responses to the 5-HT1A agonist ipsapirone (1 and 2 mg/kg), the 5-HT2C agonist m-chlorophenylpiperazine (m-CPP, 0.6 mg/kg), which also binds to other 5-HT receptors with lower affinity, and the 5-HT2A/2C agonist 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI, 1 mg/kg) in chronically cannulated, freely moving male rats. Pharmacological characterization using antagonists with different affinity for 5-HT2A and 5-HT2C receptors revealed that DOI's responses were mediated mainly by 5-HT2A receptors and m-CPP's responses were almost exclusively mediated by 5-HT2C receptors. ACTH/corticosterone responses to ipsapirone, DOI and m-CPP were almost completely blocked after PVN lesions. Prolactin responses were significantly different in lesioned rats only after DOI and m-CPP challenges. Oxytocin responses to ipsapirone and DOI, but not m-CPP were markedly attenuated after PVN lesions. The present findings suggest that the PVN, or neural pathways close to it, mediate corticosterone and in some cases prolactin and oxytocin responses to selective stimulation of 5-HT1A, 5-HT2A, or 5-HT2C receptors.

Adrenocorticotropic Hormone↗

PubMed1993

Alzheimer's disease--from cause to cure?

The tools of molecular biology have only been applied to the study of the brain since the early 1980s, but it is already apparent that this approach holds promise for identifying strategies and drugs that are able to modify the activity and function of particular neural pathways. One of the greatest prizes--both for society and commercially--will be the discovery of a safe and effective drug to treat Alzheimer's disease.

Alzheimer Disease↗

PubMed1984

Noxious inputs to supraoptic neurosecretory cells in the rat.

The effects of noxious stimuli were studied on discharge activity of the neurosecretory cells identified in the supraoptic nucleus by antidromic excitation after pituitary stimulation, in anaesthetized rats. Tail pinching excited 24% and inhibited spontaneous discharge of 6% of the 91 cells tested. Noxious heat stimuli (44-63 degrees C) applied to the hindlimb paw produced a transient excitation in 26% of the 23 cells tested. Electric stimulation of either the sciatic or cutaneous nerve with 20-Hz pulses for 1 s, at an intensity 5 times stronger than the threshold for evoking the changes in respiratory movements and blood pressure similar to those after tail pinching or noxious heat stimuli, excited about 30% of the cells tested. The excitation produced by these noxious stimuli preceded, on some occasions, the respiratory movement and blood pressure decrease which occurred concomitantly. Peristimulus time histograms of spontaneous discharges constructed during stimulation of either nerve at 1 Hz, revealed the presence of excitatory synaptic inputs in about 35% of the neurosecretory cells tested. These data indicate the existence of direct neural pathways which mediate excitatory synaptic inputs originating from nociceptors to supraoptic neurosecretory cells. Since 9 of the 22 cells which were excited by tail pinching exhibited a "phasic" pattern of spontaneous discharge which is known to characterize certain vasopressin-secreting neurones in rats, it is suggested that these excited cells were, at least in part, vasopressinergic.

Animals↗

PubMed1992

A histaminergic H2-receptor antagonist, ranitidine, blocks the suppressive vasopressin response to fear-related emotional stress in the rat.

The effects of intracerebroventricularly (i.c.v.) administered histaminergic receptor antagonists on plasma levels of vasopressin, oxytocin, prolactin and adrenocorticotrophic hormone (ACTH) after fear-related emotional stress were investigated in the male rat. Pyrilamine, a histaminergic H1-receptor antagonist did not significantly alter the suppressive vasopressin or the facilitative prolactin response to nonassociatively applied emotional stress. On the other hand, i.c.v. administered ranitidine, a histaminergic H2-receptor antagonist, blocked these responses to stress. Pyrilamine again did not significantly change the suppressive vasopressin response to the associatively applied emotional stress. However, the drug attenuated the prolactin response slightly but significantly. Ranitidine blocked the suppressive vasopressin and the facilitative prolactin responses to the associatively applied emotional stress, but the drug did not change the facilitative oxytocin or ACTH response to the stress. Suppression of motor activity during the associatively applied emotional stress was not significantly changed by either of these antagonists. These results suggest that histaminergic H2 receptors are selectively involved in the neural pathways which mediate the suppressive vasopressin and the facilitative prolactin responses to fear-related emotional stress.

Animals↗

PubMed1995

The origin of the human auditory brain-stem response wave II.

Auditory brain-stem responses (ABRs) were recorded from human subjects undergoing neurosurgical procedures which exposed the auditory nerve. Scalp recordings indicated that the latency of the negativity between waves I and II (In) and the latency of positive peak II (IIp) were shorter when the nerve was suspended in air than when the nerve was submerged in cerebrospinal fluid or saline, while earlier and later waves remained unaffected. These results could not be attributed to changes in stimulus or recording parameters or conduction velocity. Computational and somatosensory experimental evidence of stationary potentials generated by physical properties of the volume conductor, including changes in conductivity or geometry, are presented to develop a model of wave IIp generation. The results of this study suggest that wave IIp (and probably In) are manifestations of current flux asymmetries across conductivity boundaries created by the temporal bone-cerebrospinal fluid intradural space-brain-stem interfaces. The current flux asymmetries are generated as the propagating auditory nerve action potential crosses the conductivity boundaries. These results also indicate that the physical characteristics of the volume conductor and neural pathways must be considered when interpreting surface recorded evoked potentials.

Action Potentials↗

PubMed1996

Co-expression of steroid hormone receptors in opioid peptide-containing neurons correlates with patterns of gene expression during the estrous cycle.

The anteroventral periventricular nucleus (AVPV) of the preoptic region represents an essential component of neural pathways regulating gonadotropin secretion, and contains sexually dimorphic populations of neurons that express dynorphin or enkephalin. In the present study we used in situ hybridization to measure prodynorphin (PDYN) and proenkephalin (PENK) mRNA in the AVPV of intact animals killed on each day of the cycle. Levels of PDYN mRNA were lowest in animals killed on the afternoon of proestrus and then increased by over 60% by the morning of the following day. Expression of PENK mRNA was generally stable during the cycle, but a small yet significant reduction was detected on proestrus relative to levels of PENK mRNA in animals killed on the day of diestrus. In addition, we used double in situ hybridization to demonstrate that the majority of PDYN mRNA-containing neurons express both estrogen (50%) and progesterone receptor (85%) mRNAs. Only one quarter of the PENK-containing neurons also co-express estrogen receptor mRNA, and fewer than 10% of the PENK mRNA neurons express PR mRNA. Thus, the differential expression of PDYN and PENK during the cycle generally correlates with distinct differences in the degree of colocalization of ER and PR mRNA in PDYN and PENK mRNA-containing neurons in the AVPV.

Animals↗

PubMedDate not supplied

Inhibitory effect of ceruletide on haloperidol-induced catalepsy in rats.

Ceruletide (CLT: 160 micrograms/kg, SC) produced a relatively long-lasting inhibition of haloperidol (HPD: 2 mg/kg, PO) catalepsy in rats. Neither bilateral vagotomies nor hypophysectomy abolished the anticataleptic effect of CLT. However, (-)-L-364,718 and proglumide blocked the effect of CLT. CLT (160 micrograms/kg) significantly inhibited HPD (2 mg/kg)-induced increase in dopamine (DA) release from the rat striatum. This effect of CLT was also antagonized by proglumide. These results suggest that CLT (160 micrograms/kg) primarily acts on cholecystokinin-A receptor in the brain, exerts some modulatory influence on HPD binding to striatal DA receptors via unknown neural pathways and, consequently, inhibits HPD catalepsy.

3,4-Dihydroxyphenylacetic Acid↗

PubMedDate not supplied

Mechanism of noncholinergic excitation of canine ileal circular muscle by motilin.

In the isolated perfused canine ileal segment, exogenous motilin infused for 9 min, at concentrations from 10(-10) M and 10(-8) M, increased circular muscle motility concomitant with inhibiting tonic VIP release, maximum at 10(-8) M. Both effects increased with increasing motilin concentrations. Atropine 10(-7) M pretreatment did not alter these responses. Naloxone 10(-7) M pretreatment eliminated both the increase in motor activity and the inhibition of VIP levels. Thus the nonmuscarinic neural pathway responsible for motor activation by motilin probably involves the stimulation of release of opiates, which in turn inhibit the release of VIP. Reduction of tonic inhibition of the muscle by continuous VIP release may in part account for increases in motor activity induced by motilin.

Animals↗

PubMed1983

Newer concepts of analgesia and anesthesia.

Intracerebroventricular (ICV) administration of the peptidase inhibitors amastatin, trasylol, bacitracin, or phe-D-ala and systemic administration of phenylmethylsulfonyl fluoride resulted in one or more of the following responses: analgesia, reduced withdrawal severity in opiate tolerant rats, alterations in motor activity and behavior, hypo- and hyperthermia and others; some of these effects were antagonized by naloxone, suggesting participation of opioid and other endogenous peptides. In addition, peptidase inhibitors enhanced analgesic and other responses to opioid peptides given ICV. Peptidase inhibition affords another method of inducing selective pharmacological responses such as pain relief in individuals resistant to other forms of therapy. ICV administration of beta-endorphin in the rat induces general anesthesia that is instantly reversed by systemic naloxone. Extensions of this work include identification of specific neural pathways that mediate anesthesia and characterization of opiate receptor subtype(s) at these sensitive loci. This approach offers the potential for the design of systemically effective opioid peptide anesthetics with little or no secondary effects and rapid reversibility.

Analgesia↗

PubMed1996

Individual and combined effects of ethanol and cocaine on intracellular signals and gene expression.

1. Ethanol and cocaine are drugs of abuse that can produce long-lived changes in behavior, including dependence. 2. A common set of neural pathways appears to mediate the addictive actions of ethanol and cocaine. 3. Many prominent aspects of drug dependence may be the result of alterations in intracellular signals as well as specific patterns of gene expression. 4. For instance, changes in G proteins and cAMP, phosphorylation of proteins and induction of c-fos and zif/268 in specific drug-sensitive brain regions may represent adaptive changes in response to a drug-dependent state. 5. The concurrent use of ethanol and cocaine is the most prevalent pattern of drug abuse in humans. However, the number of studies investigating the behavioral and molecular effects of this combination are few. 6. Emerging evidence indicates a possible antagonistic effect of ethanol and cocaine action on transcription factor function. In addition, cocaethylene (a psychoactive metabolite derived from combined ethanol and cocaine exposure) has significant effects on gene expression as well.

Animals↗

PubMed1988

Intra-arterially administered vasopressin inhibits nocturnal pineal melatonin synthesis in the rat.

1. In order to investigate the possible involvement of arginine-vasopressin (AVP) in the inhibition of nocturnal pineal melatonin synthesis following electrical stimulation of the hypothalamic paraventricular nuclei, adult male rats received injections of 5 micrograms/100 g body weight of the peptide during either day- or night-time. Following survival times of 30 or 120 min, animals were killed and the activity of the melatonin synthesis enzyme N-acetyltransferase (NAT) was determined. 2. At night, NAT activity was significantly decreased 30 and 120 min following AVP injection. 3. During the daytime, NAT activity was unchanged following AVP administration. 4. It is suggested that pineal melatonin synthesis may be affected by PVN stimulation not only via neural pathways but possibly also by PVN-released blood-borne AVP.

Animals↗

PubMed1996

Neurochemical modulation of cardiovascular control in the nucleus tractus solitarius.

The central control of cardiovascular function has been keenly studied for a number of decades. Of particular interest are the homeostatic control mechanisms, such as the baroreceptor heart-rate reflex, the chemoreceptor reflex, the Bezold-Jarisch reflex and the Breuer-Hering reflex. These neurally-mediated reflexes share a common termination point for their respective centrally-projecting sensory afferents, namely the nucleus tractus solitarius (NTS). Thus, the NTS clearly plays a critical role in the integration of peripherally initiated sensory information regarding the status of blood pressure, heart rate and respiratory function. Many endogenous neurochemicals, from simple amino acids through biogenic amines to complex peptides have the ability to modulate blood pressure and heart rate at the level of the NTS. This review will attempt to collate the current knowledge regarding the roles of neuromodulators in the NTS, the receptor types involved in mediating observed responses and the degree of importance of such neurochemicals in the tonic regulation of the cardiovascular system. The neural pathway that controls the baroreceptor heart-rate reflex will be the main focus of attention, including discussion of the identity of the neurotransmitter(s) thought to act at baroafferent terminals within the NTS. In addition, this review will provide a timely update on the use of recently developed molecular biological techniques that have been employed in the study of the NTS, complementing more classical research.

Animals↗

PubMed1982

Cobalt destroys neurons without destroying fibers of passage in the lateral geniculate nucleus of the cat.

When several injections of 4 mM cobalt chloride are made into the lateral geniculate nucleus of the cat, cell somata are destroyed while fibers-of-passage are spared. Nissl and Wiel stains were used to assess the extent of cell and fiber damage, respectively, for cobalt lesions of layer A. Retrograde transport of horseradish peroxidase from the visual cortex to geniculate cells surrounding the lesions was used to demonstrate the integrity of fibers passing through the area depleted of cells. Cobalt provides a versatile and precise method of disrupting neural pathways. Depending upon the number and timing of the injections, the disruption can be temporary, resulting from a reversible inactivation of synaptic transmission, or permanent, caused by soma death.

Animals↗

PubMed1988

Long-latency baroreceptor inhibition of supraoptic neurones in the cat.

Experiments were done to determine the central delay to inhibition of supraoptic neurosecretory neurones by carotid baroreceptors in chloralose-anaesthetised, paralysed cats. Fourteen out of 18 neurosecretory cells (identified by antidromic activation from the pituitary neural lobe) were tested for their response to inflation of the ipsilateral carotid sinus (prepared as a blind sac). This stimulus inhibited the spontaneous activity of 10 neurones, which were thus identified as putative vasopressin cells. Repetitive, precisely timed pressure pulses were delivered to the carotid sinus and used to construct post-stimulus histograms of this inhibition. The latency measured from the baroreceptor afferent barrage (recorded from the sinus nerve) to the onset of inhibition in supraoptic neurones was 251 +/- 58 ms (range 152-328, n = 10). The significance of this long latency for the neural pathways involved is discussed.

Afferent Pathways↗