[Effect of high flow nasal catheter oxygen to prevent hypoxemia in endoscopic retrograde cholangiopancreatography surgery in aged]

Objective: To explore the effect of high-flow nasal catheter oxygen inhalation in preventing hypoxemia during endoscopic retrograde cholangiopancreatography (ERCP) surgery in elderly patients. Methods: From September 2021 to September 2022, 116 elderly patients (aged ≥ 70 years) who underwent elective ERCP in the Northern Theater General Hospital were prospectively selected, then divided into general nasal catheter oxygen inhalation group [group C, 31 males and 27 females, aged (79.8±6.4) years] and high-flow nasal catheter oxygen inhalation group [group H, 33 males and 25 females, aged (81.4±6.7) years], with 58 patients in each group. All patients were monitored for anesthesia by target-controlled infusion of propofol and remifentanil. The main outcome index was the incidence of intraoperative subclinical hypoxemia (90% ≤ SpO2 < 95%, duration >5 s), hypoxemia (75% < SpO2 < 90%, 5 s < duration ≤ 60 s) and severe hypoxemia (SpO2 < 75% or SpO2 < 90%, duration > 60 s). Secondary observation measures were SpO2 from T0 to T5 (T0, before anesthesia induction; T1, immediately after anesthesia induction; T2, endoscopic introduction; T3, duodenal papula intubation; T4, endoscopic withdrawal; T5, postoperative awakening), the arterial oxygen partial pressure (PaO2), carbon dioxide partial pressure (PaCO2) and pH at T0, 15 min after the induction and T5. Results: The incidence of intraoperative subclinical hypoxemia in group C and group H was 12.0% (7/58) and 3.4% (2/58) respectively, which showed no significant statistical difference (P=0.165) from each other. The incidence of intraoperative hypoxemia in group H was 8.6% (5/58), which was significantly lower than 31.0% (18/58) of group C (P=0.003). Neither group had intraoperative severe hypoxemia. SpO2 of group H were (98.2±0.9)%, (98.2±0.9)%, (97.8±1.7)% and (97.7±1.7)% at T1, T2, T3, T4, which were higher than (96.8±2.1)%, (96.4±3.0)%, (96.1±2.9)% and (96.4±3.4)% in group C (all P<0.05). PaO2 at 15 min after induction in group H was (240.5±46.7) mmHg (1 mmHg=0.133 kPa), which was higher than that of group C (170.6±33.4) mmHg (P<0.001). There was no statistically significant difference in pH and PaCO2 between the two groups of patients at each timepoint. Conclusion: High flow nasal catheter oxygen can effectively reduce the incidence of hypoxemia in ERCP in elderly patients.

Comparison of in-hospital outcomes and 30-days readmissions between type 1 and type 2 myocardial infarction patients: a study of the nationwide readmissions database

Introduction

Traditionally Type- 1 myocardial infarction (T1-MI) results from a plaque erosion, rupture, or fissure. In contrast, Type- 2 myocardial infarction (T2-MI) is a consequence of severe supply and demand mismatch. Despite the different mechanisms, both T1-MI and T2-MI can be associated with severe morbidity and mortality. Yet there is sparse data analyzing in-hospital outcomes and readmission rates comparing patients who present with T1-MI and T2-MI.

Purpose

We aimed to compare the outcome data of patients with T1-MI and T2-MI derived from the Nationwide Readmissions Database, a large national database of hospital readmissions.

Method

We utilized the 2018 Nationwide Readmissions Database to identify all index hospital admissions with a primary diagnosis of “acute MI” (AMI) using ICD-10 diagnosis codes. All AMI admissions were further categorized into ST-elevation myocardial infarction (STEMI), no-ST-elevation myocardial infarction (NSTEMI), or T2-MI. Primary outcomes analyzed included 30-days major adverse cardiovascular events (MACE) (defined as re-infarction, repeat revascularization and death within 30 days of admission), short term mortality and readmission rates.

Results

Among 556,816 total admissions for AMI, 28,250 (5.1%) were T2-MI. Table 1 compares baseline variables and short-term outcomes for patients with T1-MI vs T2-MI. Compared to patients with T1-MI patients with T2-MI were older, more likely to be female, and had a higher burden of comorbidities. Additionally, T2-MI patients were less likely to receive coronary revascularization during the index admission. The mean length of stay for T2-MI patients was 4.7±0.6 days, which is longer than the length of stay for STEMI patient (4.1±0.4 days) but slightly shorter than NSTEMI patient (4.9±0.4 days). T2-MI patients had a higher rate of all-cause 30-days readmissions but a lower rate of 30-days MACE. Early mortality rate (within 30 days of index admission) in T2-MI patients was comparable to NSTEMI patients but was lower than STEMI patients. Cox proportional-hazards model adjusting for age, sex, comorbidities and type of hospital setting demonstrated that T2-MI was associated with a lower 30-day MACE risk (T2-MI vs STEMI: [HR 0.33 (95% CI 0.31–0.36)]; T2-MI vs NSTEMI [HR 0.70 (95% CI 0.64–0.75)]) and a lower risk of early mortality (T2-MI vs STEMI: [HR 0.29 (95% CI 0.26–0.32)]; T2-MI vs NSTEMI [HR 0.71 (95% CI 0.65–0.79)]). The adjusted HR for 30-days all-cause readmissions was higher with T2-MI, (T2-MI vs STEMI: [HR 1.16 (95% CI 1.10–1.23)]; T2-MI vs NSTEMI: [HR 1.11 (95% CI 1.06–1.16)]).

Conclusion

T2-MI patients are older and have a higher burden of comorbidities. After adjusting for baseline comorbidities, all-cause readmission risk is higher in T2-MI but short-term MACE and mortality is lower with T2-MI.

Funding Acknowledgement

Type of funding sources: None.

[Robotic hilar cholangiocarcinoma radical resection compared with laparotomy in prognosis]

Objective: To compare the long term and short term outcomes between robotic and open surgery for hilar cholangiocarcinoma radical resection. Methods: This is a single-center and retrospective case-control study. Patients underwent hilar cholangiocarcinoma radical resection between January 2016 and December 2016 at Department of Hepatobiliary Surgery of the General Hospital of the Chinese People's Liberation Army were included. Safety, effectiveness and long-term prognosis of tumors were evaluated. Patients were divided into robotic hilar cholangiocarcinoma radical surgery group (robotic group, n=16) and open hepatic hilar cholangiocarcinoma radical surgery group (open group, n=31) . All cases were confirmed by pathology histological. Age, gender, histology, resection margin status, extent of surgical resection, disease-free survival (DFS) , and overall survival (OS) were retrospectively collected and analyzed.In the follow-up cohort, the primary outcome was patient death and the secondary outcome was tumor recurrence. Continuous variables were expressed as means and medians and were compared using the Student t test if normally distributed or Wilcoxon-Mann-Whitney test for nonparametric variables. Discrete variables were expressed as frequency and percentages and χ(2) or Fisher exact test, when appropriate, were used for comparisons. Kaplan-Meier curves were used to calculate the probability of survival and comparisons were performed using log-rank test. Results: In this study, compared with the open group, the robotic group had a longer operation time ( (338±71) minutes vs. (256±56) minutes, t=4.251, P=0.001) , but the intraoperative blood loss was less (100 ml vs. 200 ml, Z=121.50, P=0.040) , the gastric tube removal time was earlier (3 days vs. 4 days, Z=136.0, P=0.011) , and the postoperative hospital stay was shorter (9 days vs. 12 days, Z=144.50, P=0.040) , and the difference was statistically significant.There was no significant difference in the blood transfusion rate, R0 resection rate, and tumor size between the two groups.The recurrence rates in the robotic group and open surgery were 53.3% and 67.0%, respectively (χ(2)=1.04, P=0.307) .The median survival time of the robotic group and the open group was 22.0 months and 25.0 months. There was no significant difference in the overall survival rate between the two groups (P>0.05) . Conclusion: Compared with laparotomy, robotic HCC radical resection could have an equivalence or non-inferiority approach with acceptable long-term outcome.

[The clinical analyses of neuromyelitis optica spectrum disorder initially presenting with area postrema syndrome in 14 patients]

Objective: To explore the clinical characteristics of the neuromyelitis optica spectrum disorders (NMOSD) with the area postrema syndrome as the initial symptom. Methods: A total of 14 cases were enrolled in the study with the diagnose of NMOSD and the area postrema syndrome as the initial symptom. All the clinical data and imaging profiles by the contrasted magnetic resonance imaging (MRI) of the head and spinal cord were collected and analyzed. Results: The median age of onset was (38.1±17.0) years old and the gender ratio of female to male was 10∶4. The serum aquaporin-4(AQP4)-IgG was positive in 11 subjects and several autoimmune antibodies was positive in 7 subjects. The lesions revealed by MRI of the head mainly located in the area postrema and ependymal periphery which often presented as the linear medullary lesion, while linear lesions over three pieces of vertebra were shown by MRI of the spinal cord which mainly in the grey matter and with a"H" shape around the spinal central canal. Misdiagnose happened in 11 subjects with seven of gastroesophageal reflux disease, two of neurogenic vomiting, one of spinal cord tuberculosis and one of stroke. Conclusions: NMOSD should be considered in patients with unexplained intractable nausea, vomiting and/or hiccups lasted for 48 hours or above, especially in those with positive nervous signs. Contrasted MRI and serum AQP4-IgG need to be performed in the suspected patients. Early detection is crucial for patients with NMOSD.

[Analysis of the clinical features of vestibular migraine with MRI changes]

Objective: To investigate the clinical features of vestibular migraine with MRI changes. Methods: The clinical data of 150 patients with vestibular migraine completing MRI examination in navy general hospital from August 2008 to August 2016 were retrospectively analyzed.Clinical features of 94 (62.7%) vestibular migraine patients with MRI changes were collected and analyzed according to the medical history, clinical symptoms and signs, as well as the result of auxiliary examinations. Results: The manifestations of MRI in vestibular migraine patients were mainly multiple punctate equal T(1) and long T(2) signals or high signals on FLAIR (fluid attenuated inversion recovery) in subcortical white matter. The average age of the patients at the visit was (52±15) years old, with the male to female ratio of 1∶3.1. The occurrence of vertigo and migraine were in no particular order, with 54.3% patients presenting migraine several years before vertigo. The duration of vertigo was mostly 24 hours to 72 hours (31.9%). The visual aura (55.3%), photophobia and phonophobia (67.0%) were the most frequently associated symptoms. Conclusions: The vestibular migraine patients with MRI changes have its own specific clinical characteristics and are mainly seen in female with visual aura. The associated symptoms of vestibular migraine appear mostly during the process of vertigo. The pathogenesis of cerebral white matter hyperintensities (WMHs) is not clear.

Probabilistic reversal learning is impaired in Parkinson's disease

In many everyday settings, the relationship between our choices and their potentially rewarding outcomes is probabilistic and dynamic. In addition, the difficulty of the choices can vary widely. Although a large body of theoretical and empirical evidence suggests that dopamine mediates rewarded learning, the influence of dopamine in probabilistic and dynamic rewarded learning remains unclear. We adapted a probabilistic rewarded learning task originally used to study firing rates of dopamine cells in primate substantia nigra pars compacta [Morris G, Nevet A, Arkadir D, Vaadia E, Bergman H (2006) Midbrain dopamine neurons encode decisions for future action. Nat Neurosci 9:1057-1063] for use as a reversal learning task with humans. We sought to investigate how the dopamine depletion in Parkinson's disease (PD) affects probabilistic reward learning and adaptation to a reversal in reward contingencies. Over the course of 256 trials subjects learned to choose the more favorable from among pairs of images with small or large differences in reward probabilities. During a subsequent otherwise identical reversal phase, the reward probability contingencies for the stimuli were reversed. Seventeen PD patients of mild to moderate severity were studied off of their dopaminergic medications and compared to 15 age-matched controls. Compared to controls, PD patients had distinct pre- and post-reversal deficiencies depending upon the difficulty of the choices they had to learn. The patients also exhibited compromised adaptability to the reversal. A computational model of the subjects' trial-by-trial choices demonstrated that the adaptability was sensitive to the gain with which patients weighted pre-reversal feedback. Collectively, the results implicate the nigral dopaminergic system in learning to make choices in environments with probabilistic and dynamic reward contingencies.

Microglial response is poorly correlated with neurodegeneration following chronic, low-dose MPTP administration in monkeys

Many investigators have reported extensive microglial activation in the mouse substantia nigra and striatum following acute, high-dose 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) administration. Our previous work demonstrated tyrosine hydroxylase (TH)-positive fiber sprouting in the striatum in monkeys that had received a partial dopaminergic lesion using a low-dose, chronic MPTP administration paradigm. To characterize the microglial response, we utilized HLA-DR (LN3) to immunolabel the class II major histocompatibility complex (MHC II). In MPTP-treated monkeys, there was an intense microglial response in the substantia nigra, nigrostriatal tract, and in both segments of the globus pallidus. This response was morphologically heterogeneous, with commingled ramified, activated, and multicellular morphologies throughout the extent of these basal ganglia structures. Surprisingly, there was little evidence of microglial reactivity in the striatum despite evidence of neurodegeneration-by silver labeling and by loss of TH immunolabeling. Moreover, this pattern of microglial reactivity was the same in all animals that had received MPTP and seemed to be independent of the degree of neurotoxin-induced neurodegeneration. Thus, we conclude that microglial reactivity, per se, is not consistently associated with neurodegeneration, but depends on regional differences.

Striatal responses to partial dopaminergic lesion: evidence for compensatory sprouting

Dopaminergic lesions result in the acute loss of striatal dopamine content, the loss of tyrosine hydroxylase-immunoreactive fibers, upregulation of preproenkephalin mRNA expression, and compensatory changes in the synthesis and metabolism of dopamine. Despite the severe loss of fine tyrosine hydroxylase-immunoreactive fibers, larger fibers persist. We found that some tyrosine hydroxylase fiber types increase their branching and become thicker after partial lesion. To determine whether the remaining tyrosine hydroxylase fibers were degenerative or part of a compensatory response, we morphologically characterized striatal tyrosine hydroxylase fibers and compared them to silver-stained degenerative structures. Branched and large tyrosine hydroxylase fiber types were nondegenerative. Furthermore, normal preproenkephalin mRNA expression was maintained despite severe overall loss of tyrosine hydroxylase fibers in striatal regions with abundant branching, whereas preproenkephalin mRNA expression increased in severely depleted regions that lacked branched fibers, indicating that branching or sprouting was involved in the compensation for dopamine depletion and the maintenance of normal preproenkephalin expression. In support of compensatory sprouting by tyrosine hydroxylase fibers, mRNA for growth associated protein-43 was upregulated in dopaminergic midbrain cells. We conclude that an important compensatory response to partial dopaminergic depletion is the formation of new branches or sprouting.

Mutation of aspartic acid residues in the fructosyltransferase of Streptococcus salivarius ATCC 25975

The site-directed mutated fructosyltransferases (Ftfs) of Streptococcus salivarius ATCC 25975, D312E, D312S, D312N and D312K were all active at 37 degrees C, indicating that Asp-312 present in the 'sucrose box' was not the nucleophilic Asp residue responsible for the formation of a covalent fructosyl-enzyme intermediate required for enzyme activity. Analysis of the kinetic constants of the purified mutated forms of the enzyme showed that Asp-312 was most likely an essential amino acid involved in determining acceptor recognition and/or stabilizing a beta-turn in the protein. In contrast, when the Asp-397 of the Ftf present in the conserved triplet RDP motif of all 60 bacterial and plant family-32 glycosylhydrolases was mutated to a Ser residue, both sucrose hydrolysis and polymerization ceased. Tryptophan emission spectra confirmed that this mutation did not alter protein structure. Comparison of published data from other site-directed mutated enzymes implicated the Asp residue in the RDP motif as the one that may form a transient covalent fructosyl intermediate during the catalysis of sucrose by the Ftf of S. salivarius.

Purification and enzymic properties of the fructosyltransferase of Streptococcus salivarius ATCC 25975

The recombinant fructosyltransferase (Ftf) of Streptococcus salivarius was expressed in Escherichia coli and purified to electrophoretic homogeneity after a combination of adsorption, ion-exchange and gel-filtration chromatography. The N-terminal signal sequence of the Ftf was removed by E. coli at the same site as in its natural host. The purified Ftf exhibited maximum activity at pH 6.0 and 37 degrees C, was activated by Ca2+, but inhibited by the metal ions Cu2+, Zn2+, Hg2+ and Fe3+. The enzyme catalysed the transfer of the fructosyl moiety of sucrose to a number of acceptors, including water, glucose and sucrose via a Ping Pong mechanism involving a fructosyl-enzyme intermediate. While this mechanism of catalysis is utilized by the levansucrases of Bacillus subtilis and Acetobacter diazotrophicus and the values of the kinetic constants for the three enzymes are similar, sucrose was a far more efficient fructosyl-acceptor for the Ftf of S. salivarius than for the two other enzymes.

The value of cerebrospinal fluid antiviral antibody in the diagnosis of neurologic disease produced by varicella zoster virus

We studied four patients with subacute to chronic varicella zoster virus (VZV) infection of the central nervous system (CNS). VZV infection was verified by detecting antibody to VZV in the cerebrospinal fluid (CSF). VZV caused myelitis in two patients and encephalitis in two patients. In one of the patients with VZV encephalitis, in addition to VZV IgM antibody, VZV DNA was found in the CSF. Among the four patients with VZV infection of the CNS, CSF antibody to VZV was the crucial diagnostic laboratory test which corroborated the clinical features, and indicated that VZV caused neurologic disease. In addition to looking for amplifiable VZV DNA in the CSF of patients with neurologic disease whose clinical and radiologic features suggest VZV infection, we also recommend a search for CSF antibody to VZV, particularly in patients with intervals of weeks to months between zoster and the onset of neurologic disease, or in those patients without rash in whom the tempo of illness is unknown.

The development of enkephalin and substance P neurons in the basal ganglia: insights into neostriatal compartments and the extended amygdala

To study the comparative development of the two major neuropeptide genes of the striatum, we used immunocytochemistry to detect immunoreactivity (ir) for substance P and synenkephalin (the N terminus of proenkephalin), and in situ hybridization to detect proenkephalin mRNA. Earliest detection of substance P-ir was in the anlage of the bed nucleus of the stria terminalis (BST, at E15) and in the rostral-lateral caudate-putamen (CPu), at E16. Substance P in the BST was immediately subjacent to the medial ganglionic eminence, while immunoreactivity in the CPu was associated with the lateral ganglionic eminence. Earliest detection of synenkephalin-ir or proenkephalin mRNA was in the caudal-lateral CPu and the adjacent central nucleus of the amygdala (Ce), at E16. Over the next several days, expression of each neuropeptide spread toward the region of first expression of the other neuropeptide. The first overlap of expression of the two neuropeptides was at E18, at the level of the septum. Despite correspondence of substance P-ir and proenkephalin mRNA in patches at P0, very little co-expression of the two neuropeptides was evident in individual neurons. We propose a model in which the CPu develops primarily from the lateral ganglionic eminence, and the extended amygdala develops primarily from the medial ganglionic eminence. Within each structure, two poles of neuropeptide gene expression are established initially: substance P-ir in the rostral CPu and in the rostral-medial pole of the extended amygdala (represented by the BST), and synenkephalin/proenkephalin in the caudal CPu and in the caudal-lateral pole of the extended amygdala (represented by the Ce). A stream of substance P-ir cells connects the two poles of the extended amygdala, in the sublenticular substantia innominata.

Genesis and migration patterns of neurons forming the patch and matrix compartments of the rat striatum

The mammalian striatum is divided into two compartments, the patch (or striosome) and the matrix, which differ on the basis of several cytochemical markers, connection patterns, and time of neurogenesis. In the rat, the patch compartment consists of clusters of neurons isolated by matrix neurons; included in the patch compartment is a rim of neurons subjacent to the corpus callosum and external capsule, called the subcallosal streak. To study the genesis and migration patterns of striatal neurons forming these compartments, we injected pregnant rats with 5-bromo-2'-deoxyuridine (BrdU, which is incorporated into DNA during S-phase mitosis) on embryonic (E) day 14, to label patch neurons, or on E19, to label matrix neurons. Embryos were sacrificed at intervals after injection, for detection of BrdU by immunocytochemistry. Cells labeled at E14 were distributed fairly uniformly in the differentiated portion of the caudate-putamen through E19. However, by the day of birth (P0), E14-labeled cells were clustered into patches and the subcallosal streak. Using double immunocytochemistry for BrdU and for the patch marker substance P, we demonstrated a caudal-rostral gradient in the birth dates of neurons in the patch compartment; E14-labeled cells occupied substance P-labeled patches at the level of the posterior limb of the anterior commissure, but patches further rostral were nearly devoid of E14-labeled cells. The distance between the lateral ventricle and the nearest E14-labeled cells was greater on E19 than on E16 or on P0, suggesting secondary movement of early-born neurons during the process of cluster formation. Neurons labeled at E19 formed the matrix surrounding clusters of unlabeled cells, except in the nucleus accumbens (ventral striatum), where E19-labeled cells formed clusters. The data suggest that the uniformly-distributed population of early-born neurons is disrupted by the invasion of later-born (matrix) neurons, forcing the early-born neurons into clusters which are displaced toward the ventricular surface to form the patch compartment. Early-born neurons adjacent to the external capsule are not displaced, forming the subcallosal streak.

Ontogeny of the proenkephalin system in the rat corpus striatum: its relationship to dopaminergic innervation and transient compartmental expression

The earliest detection of the proenkephalin gene was on embryonic day 16 in neuronal cell bodies in the ventrolateral portion of the caudal neostriatum. This expression was identified by both immunocytochemistry for synenkephalin, the nonopioid N-terminus of proenkephalin (1-70), and preproenkephalin in situ hybridization with a complementary DNA probe. Two developmental gradients of preproenkephalin expression and synenkephalin immunoreactivity were observed: (i) a ventrolateral to dorsomedial and caudal to rostral gradient in the rostral caudate-putamen; and (ii) a ventromedial to dorsolateral and rostral to caudal gradient in the caudal caudate-putamen. Ventrolateral to dorsomedial and caudal to rostral developmental gradients of synenkephalin fiber immunoreactivity were also identified in the globus pallidus. Methionine enkephalin immunoreactivity was not consistently detectable until postnatal day 10 and 15 in the rostral and caudal globus pallidus, respectively. A transient patchy distribution of increased preproenkephalin expression from embryonic day 20 through postnatal day 5 occurred. These patches and a subcallosal streak were found to overlap partially with areas of increased tyrosine hydroxylase immunoreactivity by adjacent section analyses. The earliest detection of tyrosine hydroxylase immunoreactivity was found to coincide with that of proenkephalin on embryonic day 16, but in differing regions of the corpus striatum. Tyrosine hydroxylase immunoreactivity in the rostral caudate-putamen preceded, while in the caudal caudate-putamen it followed first expression of the proenkephalin gene. Early proenkephalin expression, by both synenkephalin immunocytochemistry and preproenkephalin in situ hybridization, was also detected in the central nucleus of the amygdala on embryonic day 16 immediately ventral to the area of expression in the caudate-putamen. Preproenkephalin expression in the olfactory tubercle and nucleus accumbens first appeared on embryonic day 20 and expression proceeded in a lateral to dorsomedial gradient continuous with the ventral part of the rostral caudal-putamen. Relatively late detection of methionine enkephalin immunoreactivity in comparison to synenkephalin possibly indicates a developmental delay in the complete enzymatic processing of the proenkephalin precursor. Differing gradients in the ontogeny of preproenkephalin expression in the rostral vs the caudal caudate-putamen suggest possible anatomical and developmental differences of these two regions. Also, transient compartmentalization of preproenkephalin expression and differences in dopaminergic innervation as detected by tyrosine hydroxylase immunoreactivity were further support for the existence of two subsets of proenkephalinergic neurons in the caudate-putamen. Contemporaneous development of preproenkephalin expression and synenkephalin immunoreactivity in the central nucleus of the amygdala with the ventral part of the caudal caudate-putamen also suggested developmental homology.(ABSTRACT TRUNCATED AT 400 WORDS)

Comparison of synenkephalin and methionine enkephalin immunocytochemistry in rat brain

Immunocytochemistry using an antiserum to the C-terminal octapeptide of synenkephalin, proenkephalin(63-70), was performed throughout the rat brain and revealed numerous immunopositive fibers and some cell bodies. The morphology and distribution of synenkephalin immunoreactivity was extremely similar to that of a commercial methionine enkephalin (Met-ENK) antiserum. Colchicine pretreatment allowed the immunostaining of cell bodies not otherwise possible without pretreatment, but did not affect the distribution of immunoreactive fibers. Using 6 microns serial sections, we were able to colocalize synenkephalin and Met-ENK immunoreactivities in gigantocellular neurons of the medullary reticular formation. Preabsorption of the antiserum with [Tyr63]proenkephalin(63-70) octapeptide (YEESHLLA) completely eliminated immunoreactivity in the rat brain, while preabsorption with all other peptides used had no detectable effect. We conclude that our antiserum to synenkephalin is specific for enkephalinergic cell bodies, fibers and terminals. The synenkephalin antiserum used in these studies may have advantages over other antisera utilized for immunocytochemical detection of proenkephalin gene expression.