The late phase of long-term potentiation (LTP) and memory (LTM) requires new gene expression, but the molecular mechanisms that underlie these processes are not fully understood. Phosphorylation of eIF2alpha inhibits general translation but selectively stimulates translation of ATF4, a repressor of CREB-mediated late-LTP (L-LTP) and LTM. We used a pharmacogenetic bidirectional approach to examine the role of eIF2alpha phosphorylation in synaptic plasticity and behavioral learning. We show that in eIF2alpha(+/S51A) mice, in which eIF2alpha phosphorylation is reduced, the threshold for eliciting L-LTP in hippocampal slices is lowered, and memory is enhanced. In contrast, only early-LTP is evoked by repeated tetanic stimulation and LTM is impaired, when eIF2alpha phosphorylation is increased by injecting into the hippocampus a small molecule, Sal003, which prevents the dephosphorylation of eIF2alpha. These findings highlight the importance of a single phosphorylation site in eIF2alpha as a key regulator of L-LTP and LTM formation.

The occurrence and origin of substance P (SP)-immunoreactive (IR) nerves in the lower respiratory tract was studied by means of immunohistochemistry in the guinea-pig, rat, cat and man. In addition, biopsies from human material were also analysed by radioimmunoassay. SP-IR nerves were seen in four principal locations: 1) under or within the lining epithelium, 2) around blood vessels, 3) within the bronchial smooth muscle layer, and 4) around local tracheobronchial ganglion cells. Ligation experiments combined with capsaicin pretreatments indicated that all SP-IR nerves in the respiratory tract are sensory. The trachea seems to be mainly supplied by the vagal nerves, while intrapulmonary bronchi and blood vessels receive SP-IR nerves of both vagal and non-vagal (spinal) origin. SP-IR nerves were also found in the human bronchi with principally similar location as in the guinea-pig. The levels of SP-IR in the trachea and peripheral bronchi of man were about 3-4 pmol/g, which is in the same range as the content of corresponding tissues from the guinea-pig. In conclusion, the present experimental findings of SP-IR nerves in the lower respiratory tract in both experimental animals and man support the functional evidence for the importance of SP in the vagal and non-vagal (spinal) control of bronchial smooth muscle tone and vascular permeability.

Binding sites for synthetic human 1251-labeled calcitonin gene-related peptide (125I-CGRP) have been demonstrated in membranes of the human nervous system. Binding was high in the cerebellar cortex (1.35 ± 0.27 fmol/mg of tissue; mean ± SEM), spinal cord (1.06 ± 0.27 to 1.27 ± 0.23 fmol/mg), and nucleus dentatus (1.02 ± 0.15 fmol/mg), intermediate in the inferior colliculus (0.80 ± 0.14 fmol/mg) and substantia nigra (0.75 ± 0.14 fmol/mg), low in the neocortex, globus pallidus, nucleus caudatus, hippocampus, amygdala, superior colliculus, thalamus, and hypothalamus (0.15-0.32 fmol/mg), and negligible in spinal and sympathetic ganglia and pituitary (<0.04 fmol/mg). Autoradiography showed distinct 1251-CGRP binding over the molecular and Purkinje cell layers of the cerebellar cortex and over the substantia gelatinosa posterior of the spinal cord. The highest levels of CGRP-like components were recognized in the dorsal part of the spinal cord and the pituitary gland. In the ventral part of the spinal cord as well as in the pituitary and thyroid glands, CGRP values were higher when measured by radioreceptorassay as compared to RIA, indicating that at least two CGRP-like components are present. The predominant CGRPlike peak on HPLC had the retention time of synthetic human CGRP. Immunohistochemistry revealed the presence of a dense plexus of CGRP immunoreactive nerve fibers in the dorsal horn of the spinal cord.The existence of rat and human calcitonin gene-related peptide (CGRP) has been predicted by analysis of the nucleotide sequence of the calcitonin gene (1, 2). CGRP is a unique 37 amino acid peptide that shares greater structural homology with salmon calcitonin-(1-32) than with rat and human calcitonin-(1-32) (1-3). Expression of CGRP was shown immunohistochemically and by specific RIA in combination with gelpermeation chromatography and HPLC in the nervous system and in the pituitary and thyroid glands (4-6). The amino acid sequence was derived from human medullary carcinoma of the thyroid (7).Here we report distinct regional distribution of CGRP and calcitonin (CT) binding sites in the human central nervous system. The presence of endogenous CGRP-like components in the nervous system, pituitary, and thyroid was revealed by a radioreceptorassay (RRA) using human cerebellar membranes, by RIA, and by immunohistochemistry. MATERIALS AND METHODSTissues and Peptides. Tissue obtained at autopsy within 20 hr postmortem was frozen on dry ice and stored at -80°C for a maximum of 3 wk. Patients with malignant tumors, chronic renal insufficiency, or metabolic bone disease were excluded from the study.Synthetic salmon CT-( Receptor Binding Studies. Membranes were prepared and incubated as described (8, 9) with 17,000 dpm (1 dpm = 16.7 mBq) of human 125I-labeled CGRP (125I-CGRP) Ci/mmol) or salmon 125I-labeled CT (125I-CT) Ci/mmol). Specific binding was defined as total binding minus binding in the presence of 0.7 ,uM unlabeled human CGRP or salmon CT, respectively. A RRA for CGRP was developed using membranes fro...