Evidence for the co-storage and co-release of neuropeptide Y and noradrenaline from large dense cored vesicles in sympathetic nerves of the bovine vas deferens

The subcellular localization and the secretion of neuropeptide Y were studied in sympathetic nerve endings of bovine vas deferens. Immunostaining revealed a parallel distribution for neuropeptide Y and dopamine-beta-hydroxylase immunoreactivity in the network of varicose nerve fibers in the smooth muscle layers of the vas deferens. Following differential centrifugation and sucrose density gradient centrifugation, neuropeptide Y was found to coincide with noradrenaline in the more dense region of the gradient, where the large dense cored vesicles are found. Superfusion experiments demonstrated the release of neuropeptide Y and noradrenaline upon electrical stimulation. Furthermore, the neuropeptide Y secretion was shown to be Ca2+-dependent. We conclude that in the bovine vas deferens neuropeptide Y is only present in large dense cored vesicles of adrenergic neurons and that the peptide and noradrenaline are co-released from these vesicles in a calcium dependent manner.     

Noradrenergic neurons release both noradrenaline and neuropeptide Y from a single pool: The large dense cored vesicles

In peripheral adrenergic nerve endings, noradrenaline is stored in two different types of vesicles, the large and the small dense cored vesicles. A systematic study was undertaken to examine the release of noradrenaline and neuropeptide Y from dog spleen and rat vas deferens under various conditions of stimulation, particularly those which previously have demonstrated a differential regulation of exocytosis of the different types of storage vesicles. Here we present evidence that noradrenaline is released by exocytosis exclusively from the large dense cored vesicles, in which it is stored together with neuropeptide Y. Upon a single stimulation (at frequencies varying from 2–20 Hz), the release of noradrenaline and neuropeptide Y from the dog splenic nerve increased with the frequency of stimulation, but the ratio of noradrenaline to neuropeptide Y remained constant. After repeated stimulation of the splenic nerve, both substances' overflow decreased gradually and in parallel to values of 12.5% and 11.1% of the first stimulation for noradrenaline and neuropeptide Y, respectively. Similarly, repeated stimulation of the rat vas deferens (of which only 2–10% is large dense cored vesicles, whereas in the dog splenic nerve the large dense cored vesicles make up 30–40% of the total vesicle population) with 120 mM K⁺, in the presence of phentolamine, caused a gradual and parallel decline in the release of noradrenaline and neuropeptide Y (31.6% and 34.0%, respectively). Moreover, ω-conotoxin (10⁻⁸ M to 10⁻⁵ M) had a similar inhibitory effect on the release of both substances, α-latrotoxin (10⁻⁹ M) evoked a parallel release of both noradrenaline and neuropeptide Y. The results indicate that noradrenaline in peripheral noradrenergic nerves is released exclusively from large dense cored vesicles by an exocytotic mechanism. Synapse 25:44–55, 1997. © 1997 Wiley-Liss, Inc.     

Increase in neuropeptide Y, but not noradrenaline, in the superior cervical ganglion of rabbits chronically exposed to cold

We have investigated the effects of exposure to cold for 8 days on sympathetic neurones supplying the ear artery of the rabbit using a combination of assay and quantitative morphological techniques. The concentration of neuropeptide Y was shown to be significantly higher in the superior cervical ganglion of cold-exposed animals. Although the noradrenaline and dopamine levels in the ganglion were not significantly changed, the ratio of noradrenaline to dopamine was significantly increased after exposure to cold. The density of noradrenergic nerves supplying the ear artery was found to be unaffected by cold exposure. Since noradrenaline and neuropeptide Y have been shown to coexist in the majority of neurones of the superior cervical ganglion, the present study appears to provide an example of differential control of expression of neurotransmitters contained within the same neurone.     

Evidence for differential localization of noradrenaline and neuropeptide Y in neuronal storage vesicles isolated from rat vas deferens

Using the technique of homogenization and subsequent density gradient centrifugation combined with ultrastructural analysis, the subcellular localization of noradrenaline and neuropeptide Y (NPY) was studied in vas deferens of castrated male rats. Noradrenaline showed two peaks in the gradient: one major peak at low density and another at high density. Only one NPY peak was seen, which coincided with the high density peak of noradrenaline. Electron microscopic analysis revealed high proportions of small and large vesicles in the light and heavy fractions, respectively. The present results indicate a differential subcellular localization of noradrenaline and NPY in the noradrenergic nerve endings of vas deferens. Thus, small vesicles seem to contain only noradrenaline, whereas the large vesicles may contain both noradrenaline and NPY.     

Differential regulation of neuropeptide Y and catecholamine production in superior cervical ganglion cultures

Primary cultures of newborn rat superior cervical ganglion (SCG) neurons grown in complete serum-free medium have been used to study the regulation of catecholamine and neuropeptide Y (NPY) production. The levels of mRNA for preproNPY and for tyrosine hydroxylase were determined, and the rates of synthesis and accumulation of NPY and catecholamines were measured. Drugs which effectively blocked accumulation of newly synthesized catecholamines (tyramine, reserpine) had no effect on NPY synthesis and accumulation. The catecholamine uptake blocker desipramine and the α₂-adrenergic receptor agonist clonidine inhibited accumulation of newly synthesized catecholamines, but only after prolonged exposure to drug; NPY synthesis and accumulation were unaltered by these treatments. The α₂-adrenergic receptor antagonist yohimbine had no effect on catecholamine or NPY synthesis or accumulation, regardless of the time of treatment. The net synthesis and accumulation of catecholamines and NPY decreased in parallel in response to treatment with phorbol esters, and increased in parallel in response to treatment with glucocorticoids; there was no change in the mRNA levels for tyrosine hydroxylase or preproNPY following either treatment. The levels of tyrosine hydroxylase or preproNPY mRNA were increased following treatment with dibutyryl cyclic AMP, with no change in the net synthesis and accumulation of catecholamines or NPY. Thus, the levels of mRNA for preproNPY and tyrosine hydroxylase are not faithful indicators of the rate of catecholamine or peptide production under several treatment conditions. The complex pattern of regulation of catecholamine and NPY production in SCG neurons grown under closely controlled conditions provides an ideal system in which to examine neuronal regulation of neurotransmitter and neuromodulator production.     

重性抑郁症患者脑脊液中P物质、神经肽Y、5-羟色胺及去甲肾上腺素含量的研究

目的从神经递质角度探讨重性抑郁症的病理生理机制。方法采用酶联免疫吸附法测定40例重性抑郁症患者(患者组)、40例对照(前列腺增生症、鞘膜积液、腹股沟疝患者及部分健康人,对照组)脑脊液中P物质(SP)、神经肽Y(NPY)、去甲肾上腺素(NE)、5-羟色胺(5-HT)及5-羟吲哚乙酸含量。结果患者组SP含量[(18±24)ng/L]高于对照组[(9±13)ng/L],差异有统计学意义(P=0.010)。患者组NE[(92±88)ng/L]高于对照组[(51±35)ng/L],差异有统计学意义(P=0.009)。患者组5-HT含量女性[(0.59±0.13)μg/L]低于男性[(0.82±0.32)μg/L],差异有统计学意义(P=0.014)。患者组有自杀行为和强烈自杀观念患者的5-HT含量低于无自杀观念患者,差异有统计学意义(P分别为0.018和0.023);有自杀行为患者的NE含量高于无自杀观念和偶有自杀观念患者,差异有统计学意义(P分别为0.029和0.017)。复发性抑郁症的NPY含量[(152±89)ng/L]明显高于首发性抑郁症[(83±32)ng/L],P=0.026。5个测定指标含量间无明显相关关系。结论重性抑郁症患者可能存在多种神经递质功能异常。     

Neuropeptide Y and [Leu,Pro]neuropeptide Y potentiate potassium-induced noradrenaline release in the paraventricular nucleus of the aged rat

This microdialysis study investigated the effects of NPY and the Y₁ selective agonist [Leu³¹,Pro³⁴]NPY on basal and potassium-stimulated noradrenaline release in the PVN of 18-month-old anaesthetised male Sprague–Dawley rats. Microdialysate noradrenaline, DOPAC and HVA concentrations were measured by HPLC after i.c.v. administration of 2 nmol NPY, [Leu³¹,Pro³⁴]NPY or vehicle. [Leu³¹,Pro³⁴]NPY produced a significant 40% reduction in basal noradrenaline concentration (P<0.05). Aged rats had blunted noradrenaline responses to potassium stimulation, however stimulated noradrenaline release was similar in 18-month-old NPY-treated animals and 3-month-old saline treated age controls (2.8 and 3.2 times resting, respectively). [Leu³¹,Pro³⁴]NPY induced a significantly greater release of noradrenaline in response to KCl (5.0 times resting, P<0.05). Thus, in 18-month-old animals with reduced endogenous hypothalamic NPY content, administration of NPY or [Leu³¹,Pro³⁴]NPY increased potassium-induced noradrenaline release to levels seen in 3-month-old rats. This effect may be mediated by an NPY Y₁ receptor.     

Methamphetamine stimulates the release of neuropeptide Y and noradrenaline from the paraventricular nucleus in rats

Effects of methamphetamine (MAP) on the extracellular neuropeptide Y (NPY) and noradrenaline (NA) levels were examined in the vicinity of the paraventricular nucleus (PVN) of freely moving rats by means of push-pull perfusion. The NA and NPY levels increased significantly in 30–60 min and reached the maximum level in 90–120 min after intraperitoneal administration of MAP. The effects were dose-dependent. The maximum levels were 1.6-fold of the pretreatment level for NPY and 7-fold for NA, respectively, when 5.0 mg/kg b.w. of methamphetamine was administered. It is concluded that MAP stimulates the releases of paraventricular NPY and NA, but the effect is more strong for NA than for NPY.     

Increased endogenous noradrenaline and neuropeptide Y release from the hypothalamus of streptozotocin diabetic rats

Noradrenaline and neuropeptide Y (NPY) in the hypothalamus regulate a number of important endocrine and autonomic functions. Alterations in brain neurotransmitter content have been described in type 1 diabetes but there is little understanding of whether these changes affect neurotransmitter release. This study examined for the first time, region-specific co-release of NPY and noradrenaline from the hypothalamus of male Sprague-Dawley rats treated intravenously with 48 mg/kg streptozotocin (STZ) or vehicle. Five weeks later, the release of endogenous noradrenaline and NPY was monitored by in vitro superfusion of ventral and dorsal hypothalamus slices under basal and potassium-stimulated conditions. STZ-diabetes induced significant increases in basal noradrenaline and NPY overflow from the ventral hypothalamus (P<0.05); only NPY overflow was increased in the dorsal hypothalamus (P<0.05). Noradrenaline overflow increased similarly to potassium depolarisation in vehicle and STZ-diabetic rats, whereas diabetic rats showed a significantly increased NPY overflow response to potassium depolarisation compared to vehicle rats. These region-specific increases in endogenous noradrenaline and NPY overflow from the hypothalamus in diabetes suggest increased neuronal activity at rest and enhanced responses under some conditions. Increased hypothalamic NPY and noradrenaline overflow most likely contributes to diabetic hyperphagia.     

Inhibition of noradrenaline release by neuropeptide Y does not involve protein kinase C in mouse atria

In this study, we investigated the possible involvement of protein kinase C in the inhibitory effect of neuropeptide Y (NPY) on the electrical stimulation-induced release of radioactivity from mouse atria incubated with [3H]-noradrenaline. The protein kinase C activators, phorbol dibutyrate (PDB, 0.001-1 mumol/l) and phorbol myristate acetate (PMA, 0.001-1 mumol/l), increased the release of noradrenaline in a concentration-dependent manner. Interestingly, the maximum effect on noradrenaline release was significantly greater for phorbol dibutyrate compared to phorbol myristate acetate. The enhancement produced by both phorbol esters was significantly reduced by the protein kinase C inhibitor, K-252a (1 mumol/l). In the presence of the concentration of either phorbol ester (PMA, 0.1 mumol/l, PDB 1 mumol/l), that was supramaximal for increasing the release of noradrenaline, NPY (0.3 mumol/l) significantly inhibited the release of noradrenaline. Moreover, in the presence of the protein kinase C inhibitors, K-252a (1 mumol/l) or polymyxin B (70 mumol/l), NPY (0.3 mumol/l) also significantly inhibited the release of noradrenaline. Therefore, it is concluded that protein kinase C is not involved in the prejunctional inhibitory effect of NPY on noradrenaline release in the mouse atria. Furthermore, since K-252a also inhibits cyclic AMP-dependent protein kinase, cyclic GMP-dependent protein kinase and myosin light chain kinase, it is likely that these kinases are also not involved in the inhibitory mechanism of NPY.     

Distribution of Met-enkephalin, Leu-enkephalin, substance P, neuropeptide Y, FMRFamide, and serotonin immunoreactivities in the optic tectum of the Atlantic salmon (Salmo salar L.)

The distribution of the neuropeptides methionine- and leucine-enkephalins, substance P, FMRFamide, neuropeptide Y, and vasoactive intestinal peptide, as well as the biogenic amine serotonin was studied in the optic tectum of the Atlantic salmon by means of immunocytochemistry. Peroxidase-antiperoxidase and indirect immunofluorescence methods were used to compare the differential laminar distribution of each of these substances. Nine parts of the optic tectum were selected for analysis on frontal sections: median, dorsolateral, and ventrolateral areas at rostral, medial, and caudal levels. Methionine- and leucine-enkephalin immunoreactive fibers were found in discrete sublayers in the following strata: stratum opticum, stratum fibrosum et griseum superficiale, stratum griseum centrale, stratum, and album centrale. Most of the substance P-, serotonin-, and vasoactive intestinal peptide-immunoreactive fibers were found in the stratum album centrale, whereas the FMRFamide- and neuropeptide Y-immunoreactive fibers were more or less randomly distributed within most of the strata of the optic tectum. Neuropeptide Y-immunoreactive cell bodies were located in the stratum periventriculare. We suggest an extrinsic origin for most of the immunoreactive fibers observed in the optic tectum, except for the neuropeptide Y-immunoreactive fibers that probably originate in the periventricular neurons. Although retinal peptidergic input to the optic tectum has been proposed in other vertebrates, there is no evidence that any of the neuropeptidelike or serotonin immunoreactive fibers in the optic tectum of the salmon should be of retinal origin. Differences and similarities with the distribution of neuropeptides in the optic tectum in representatives of other vertebrate classes are discussed.     

Stimulation of cholinergic receptor mediated secretion from the bovine adrenal medulla by neuropeptide Y

The bovine adrenal medulla has been shown to possess binding sites for neuropeptide Y (NPY) and to release NPY in response to nicotinic receptor stimulation. Therefore we chose to investigate the influence of this peptide on adrenomedullary secretion using the retrogradely perfused bovine adrenal gland. The secretion of enkephalin-like peptides, norepinephrine and epinephrine was monitored after nicotinic cholinergic receptor stimulation in the presence and absence of NPY. NPY, alone, had no effect on secretion from the adrenal gland but produced a dose dependent increase in the secretion of enkephalin-like peptides and catecholamines when the cholinergic agonist, 1,1 dimethyl-4-phenylpiperizinium iodide, was present. The increase was significant at 1 X 10(-8) M when compared to release in the absence of NPY. The stimulatory action of other cholinergic agonists (nicotine and acetylcholine) was likewise potentiated by the addition of the neuropeptide. Peptide YY and pancreatic polypeptide did not mimic the effect of NPY when examined at the same concentration. In contrast to the potentiation observed in the perfused adrenal gland, NPY (1 X 10(-8) M) inhibited the cholinergic mediated release of enkephalin-like peptides and catecholamines from cultured bovine chromaffin cells. These data suggest that NPY may have the capacity to augment cholinergic receptor mediated secretion from the bovine adrenal gland.     

Metabolic fuels, neuropeptide Y, and estrous behavior in Syrian hamsters

Of the various environmental factors influencing reproduction, food availability plays a particularly significant role, and an insufficient supply of oxidizable metabolic fuels inhibits reproduction in female mammals. When ovariectomized, steroid-primed hamsters are food deprived for 48 h, estrous behavior is suppressed. However, the specific neuroendocrine alterations that mediate the suppression of estrous behavior are unknown. Several conditions that inhibit female sexual behavior are thought to be associated with altered neuropeptide Y (NPY) activity in the brain. Intracerebroventricular (ICV) infusion of NPY inhibits estrous behavior in ovariectomized steroid-primed rats and hamsters. Furthermore, food-deprived rats have an increase in NPY mRNA in the arcuate nucleus (ARC) of the hypothalamus. Unlike rats, studies in Syrian hamsters have failed to detect any alterations in ARC NPY mRNA following food deprivation. Here we show that ARC NPY immunoreactivity and mRNA is increased in food-deprived hamsters but not in hamsters given other metabolic challenges that inhibit estrous behavior. These findings support the hypothesis that NPY contribute to, but not be critical for, the nutritional inhibition of sexual receptivity.     

Ultrastructural localization of neuropeptide Y Y1 receptors in the rat medial nucleus tractus solitarius: relationships with neuropeptide Y or catecholamine neurons

Neuropeptide Y (NPY) Y1 receptor (Y1-R) agonists influence cardiovascular regulation. These actions may involve NPY- and catecholamine-containing neurons in the medial nucleus of the solitary tract (mNTS), at the level of the area postrema. The cellular sites through which Y1-R agonists may interact with NPY and catecholamines in the mNTS, however, are not known. To determine potential sites of action for Y1-R agonists, and their relationship to NPY or catecholamines in the mNTS, we used electron microscopic immunocytochemistry for the detection of sequence-specific antipeptide antisera against Y1-R alone or in combination with antisera against NPY or the catecholamine-synthesizing enzyme tyrosine hydroxylase (TH). Analyses were conducted in the rat mNTS, at the level of the area postrema. Y1-R was found mainly in small unmyelinated axons and axon terminals but also in some somata and dendrites as well as a small number of glia. Within axon terminals, labeling for Y1-R was often present on dense core vesicles and small synaptic vesicles as well as extrasynaptic areas of the plasmalemma. Some Y1-R-labeled terminals also contained NPY or TH, suggesting that agonists of Y1-R may influence the release of NPY or catecholamines in the mNTS. In addition, Y1-R was found in dendrites that received asymmetric excitatory-type synapses from unlabeled axon terminals. Some of these dendrites contained NPY or TH, which indicates that Y1-R may be targeted for functional activation within NPY- or catecholamine-expressing neurons in the mNTS. These results demonstrate that Y1-R is a presynaptic receptor in NPY- or catecholamine-containing axon terminals within the mNTS as well as a postsynaptic receptor on NPY- or catecholamine-containing neurons that are contacted by axon terminals that likely contain excitatory amino acid transmitters. Agonists of Y1-R in the mNTS may thus affect cardiovascular regulation by modulating NPY, catecholamine, and excitatory amino acid transmission.     

Brain neuropeptide Y: an integrator of endocrine, metabolic and behavioral processes

Neuropeptide Y (NPY), acting through various medial hypothalamic nuclei, is found to have potent effects on a variety of endocrine, physiological and behavioral systems that modulate energy balance. This peptide affects the release of various hormones, such as corticosterone, insulin, aldosterone and vasopressin, which modulate energy metabolism, as well as food intake. It also has direct impact on energy metabolism through an effect on substrate utilization and lipogenesis. Finally, NPY has a remarkably potent stimulatory effect on feeding behavior, which is characterized by a selective increase in carbohydrate ingestion that is strongest at the beginning of the active feeding cycle and is dependent upon circulating levels of corticosterone. This evidence has led to the proposal that NPY exerts anabolic effects to restore energy balance at specific times of energy depletion. Increased NPY activity may occur at the beginning of the active cycle or after a period of food deprivation. Further evidence, that chronic NPY stimulation produces profound hyperphagia and obesity and that endogenous NPY concentration is increased in genetically obese animals, strongly suggests that hypothalamic NPY may contribute to the development of eating disorders and obesity.     

Cholecystokinin and neuropeptide Y receptors on single rabbit vagal afferent ganglion neurons: site of prejunctional modulation of visceral sensory neurons

A [¹²⁵I]cholecystokinin (CCK) analog and [¹²⁵I]peptide YY (PYY) were used to localize and characterize CCK and neuropeptide Y (NPY) receptor binding sites in the rabbit vagal afferent (nodose) ganglion. High concentrations of CCK and NPY binding sites were observed in 10.6% and 9.2% of the nodose ganglion neurons, respectively. Pharmacological experiments using CCK or NPY analogs suggest that both subtypes of CCK (CCK-A and CCK-B) and NPY (Y1 and Y2) receptor binding sites are expressed by discrete populations of neurons in the nodose ganglion. These results suggest sites at which CCK or NPY, released in either the nucleus of the solitary tract or a peripheral tissue, may modulate the release of neurotransmitters from a select population of visceral primary afferent neurons. Possible functions mediated by these receptors include modulation of satiety, opiate analgesia, and the development of morphine tolerance.     

Evidence against differential release of noradrenaline,neuropeptide Y,and dopamine-β-hydroxylase from adrenergic nerves in the isolated perfused sheep spleen

The subcellular storage and release of noradrenaline (NA), dopamine-β-hydroxylase (DβH), and neuropeptide Y (NPY) was studied in the isolated perfused sheep spleen. Subcellular distribution studies showed a bimodal distribution for NA which was well reflected by DβH and indicated the occurrence of two types of NA storage vesicles. The most dense, presumably large dense-cored vesicles (LDV), contain both membrane-bound and soluble DβH the less dense presumably corresponds to small dense-cored vesicles (SDV) and at least does not contain soluble DβH. The distribution of NPY is extended but shows a peak only at the position of LDV, indicating that LDV contain NPY. Continuous electrical stimulation of the splenic nerve at 2 Hz, 5 Hz, 10 Hz, and 20 Hz or at 20 hz with bursts induced the release of NA, NPY, and DβH. The ratio among these components was constant. The fractional release of DβH and NA was comparable at all frequencies used; that of NPY was 10–20 times lower, suggesting the occurrence of a large nonreleasable NPY pool. The present data argue against a high frequency stimulation or intermittent stimulation-induced preferential release of NPY from adrenergic neurons and question the concept of frequency-dependent chemical coding of sympathetic transmission in general. The simplest interpretation of our data is that NA and NPY are released at all frequencies from a single pool. The present findings might signify that only large dense-cored vesicles are involved in the sympathetic stimulation-evoked secretion of catecholamines from adrenergic nerve terminals of the isolated sheep spleen. © 1995 Wiley-Liss, Inc.     

Species differences in the expression and distribution of the neuropeptide Y Y1, Y2, Y4, and Y5 receptors in rodents,guinea pig,and primates brains

The respective distribution of neuropeptide Y Y₁, Y₂, Y₄, and Y₅ receptor subtypes was investigated in rodents (rat and mouse), guinea pig, and primates (marmoset and vervet monkeys and human) brains, representing three orders of mammals. [¹²⁵I][Leu³¹,Pro³⁴]PYY (total Y₁-like; Y₁, Y₄, and Y₅) and [¹²⁵I]PYY_3–36 (total Y₂-like; Y₂ and possibly Y₅) binding sites were discretely but similarly distributed in the rat and mouse brain, each having its unique pattern. In contrast, surprisingly low levels of [¹²⁵I]PYY_3–36 binding sites were found in the guinea pig brain including in the hippocampal formation. [¹²⁵I][Leu³¹,Pro³⁴]PYY/BIBP3226-insensitive binding sites (Y₅-like) were found in different areas of the rat and guinea pig brains. The primate brains also revealed a different distribution binding profile for these various NPY receptor subtypes. Although the human and vervet brains contained very low amounts of [¹²⁵I][Leu³¹,Pro³⁴]PYY sites (Y₁-like) in most brain regions, except for the dentate gyrus of the hippocampus, the marmoset brain contains significant amounts of both [¹²⁵I][Leu³¹,Pro³⁴]PYY (Y₁-like) and [¹²⁵I]PYY_3–36 (Y₂-like) binding sites. Additionally, [¹²⁵I][Leu³¹,Pro³⁴]PYY/BIBP3226-insensitive binding sites were not clearly detected in the vervet and human brains. On the other hand, Y₅-like binding sites were observed in few regions of the marmoset brain. Finally, [¹²⁵I]hPP (Y₄/Y₅-like) were very discretely distributed in the rat brain, being concentrated in the paraventricular nucleus of the hypothalamus and the interpeduncular nucleus. The marmoset brain is apparently not enriched with specific [¹²⁵I]hPP sites. Taken together, these data show that significant species differences exist in the level of expression and distribution of various NPY receptor subtypes in the mammalian brain. J. Comp. Neurol. 402:372–384, 1998. © 1998 Wiley-Liss, Inc.     

Subcellular distribution of neuropeptide Y-like immunoreactivity in guinea pig neocortex

Neuropeptide Y-like immunoreactivity (NPY-LI) was enriched in synaptosomal fractions of neocortex, which on lysis yielded vesicle-rich fractions. The distribution of NPY-LI on a sucrose density gradient was similar to that of somatostatin, with a concentration in heavy vesicles. The peptides were not found in light vesicles in contrast to the distribution of noradrenaline. Both homogenate and vesicular NPY-LI coeluted with synthetic NPY on reverse-phase HPLC.     

Y1 receptors in the nucleus accumbens: Ultrastructural localization and association with neuropeptide Y

Neuropeptide Y (NPY) is present in aspiny neurons in the nucleus accumbens (NAc), which also contains moderate levels of ligand binding and mRNA for the Y1 receptor. To determine the potential functional sites for receptor activation, we examined the electron microscopic immunocytochemical localization of antipeptide antisera against the Y1 receptor in the rat NAc. We also combined immunogold and immunoperoxidase labeling to show that, in this region, Y1 receptors are present in certain somatodendritic and axonal profiles that contain NPY or that appose NPY containing neurons. The Y1-like immunoreactivity (Y1-LI) was seen occasionally along plasma membranes but was associated more commonly with smooth endoplasmic reticulum (SER) and tubulovesicular organelles in somata and dendrites of spiny and aspiny neurons. The mean density of immunoreactive dendrites and spines per unit volume was greater in the “motor-associated” core than in the shell of the NAc. Y1-LI was also seen in morphologically heterogenous axon terminals, including those forming asymmetric excitatory-type synapses, and in selective astrocytic processes near this type of junction. We conclude that Y1 receptors play a role in autoregulation of NPY-containing neurons but are also likely to be internalized along with endogenous NPY in NAc. Our results also implicate Y1 receptors in the NAc in post- and presynaptic effects of NPY and in glial functions involving excitatory neurotransmission. In addition, they suggest involvement of Y1 receptors in determining the output of a select population of neurons associated with motor control in the NAc core. J. Neurosci. Res. 52:54–68, 1998. © 1998 Wiley-Liss, Inc.