Endorphins are endogenous opioid neuropeptides and peptide hormones in humans and other animals. They are produced and stored in the pituitary gland. The classification of molecules as endorphins is based on their pharmacological activity, as opposed to a specific chemical formulation.
Lumbar puncture (LP), also known as a spinal tap, is a medical procedure in which a needle is inserted into the spinal canal, most commonly to collect cerebrospinal fluid (CSF) for diagnostic testing. The main reason for a lumbar puncture is to help diagnose diseases of the central nervous system, including the brain and spine. Examples of these conditions include meningitis and subarachnoid hemorrhage. It may also be used therapeutically in some conditions. Increased intracranial pressure is a contraindication, due to risk of brain matter being compressed and pushed toward the spine. Sometimes, lumbar puncture cannot be performed safely. It is regarded as a safe procedure, but post-dural-puncture headache is a common side effect.
An enkephalin is a pentapeptide involved in regulating nociception in the body. The enkephalins are termed endogenous ligands, as they are internally derived and bind to the body's opioid receptors. Discovered in 1975, two forms of enkephalin have been found, one containing leucine ("leu"), and the other containing methionine ("met"). Both are products of the proenkephalin gene.
Ziconotide, also called intrathecal ziconotide (ITZ) because of its administration route, is an atypical analgesic agent for the amelioration of severe and chronic pain. Derived from Conus magus, a cone snail, it is the synthetic form of an ω-conotoxin peptide. It is 1,000 times as powerful as morphine.
Beta-Endorphin or β-Endorphin, is an endogenous opioid neuropeptide and peptide hormone that is produced in certain neurons within the central nervous system and peripheral nervous system. It is one of three endorphins that are produced in humans, the others of which include α-endorphin and γ-endorphin.
The periaqueductal gray is a nucleus that plays a critical role in autonomic function, motivated behavior and behavioural responses to threatening stimuli. PAG is also the primary control center for descending pain modulation. It has enkephalin-producing cells that suppress pain.
Opioid peptides are peptides that bind to opioid receptors in the brain; opiates and opioids mimic the effect of these peptides. Such peptides may be produced by the body itself, for example endorphins. The effects of these peptides vary, but they all resemble those of opiates. Brain opioid peptide systems are known to play an important role in motivation, emotion, attachment behaviour, the response to stress and pain, and the control of food intake.
Opiorphin is an endogenous chemical compound first isolated from human saliva. Initial research with mice shows the compound has a painkilling effect greater than that of morphine. It works by stopping the normal breakup of enkephalins, natural pain-killing opioids in the spinal cord. It is a relatively simple molecule consisting of a five-amino acid polypeptide, Gln-Arg-Phe-Ser-Arg.
Met-enkephalin, also known as metenkefalin (INN), sometimes referred to as opioid growth factor (OGF), is a naturally occurring, endogenous opioid peptide that has opioid effects of a relatively short duration. It is one of the two forms of enkephalin, the other being leu-enkephalin. The enkephalins are considered to be the primary endogenous ligands of the δ-opioid receptor, due to their high potency and selectivity for the site over the other endogenous opioids.
Neurogranin is a calmodulin-binding protein expressed primarily in the brain, particularly in dendritic spines, and participating in the protein kinase C signaling pathway. Neurogranin is the main postsynaptic protein regulating the availability of calmodulin, binding to it in the absence of calcium. Phosphorylation by protein kinase C lowers its binding ability. NRGN gene expression is controlled by thyroid hormones. Human neurogranin consists of 78 amino acids.
Hypoalgesia or hypalgesia denotes a decreased sensitivity to painful stimuli.
Prostaglandin-H2 D-isomerase (PTGDS) is an enzyme that in humans is encoded by the PTGDS gene.
RB-101 is a drug that acts as an enkephalinase inhibitor, which is used in scientific research.
A spontaneous cerebrospinal fluid leak is a cerebrospinal fluid leak – a leak of cerebrospinal fluid that surrounds the brain and spinal cord from the protective dural sac for no apparent reason. The dura mater is the tough, outermost of layer of the meninges, the membranes surrounding the brain and spinal cord.
A cerebrospinal fluid leak is a medical condition where the cerebrospinal fluid (CSF) surrounding the brain or spinal cord leaks out of one or more holes or tears in the dura mater. A cerebrospinal fluid leak can be either cranial or spinal, and these are two different disorders. A spinal CSF leak can be caused by one or more meningeal diverticula or CSF-venous fistulas not associated with an epidural leak.
Derek Smyth is a British biochemist who specialises in peptide structure and function. In 2002, he was admitted as a Fellow of the Royal Society of Chemistry.
Kelatorphan is a drug which acts as a powerful and complete inhibitor of nearly all of the enzymes responsible for catabolism of the endogenous enkephalins, including neutral endopeptidase (NEP), dipeptidyl peptidase III (DPP3), aminopeptidase N (APN), and angiotensin-converting enzyme (ACE). In mice, with the intracerebroventricular co-administration of a 50 µg dose of kelatorphan (this route is necessary because kelatorphan is incapable of crossing the blood-brain-barrier) hence alongside exogenous [Met]enkephalin (ED50 approximately 10 ng), it potentiated the analgesic effects of the latter by 50,000 times. Kelatorphan also displays potent antinociceptive effects alone, and does not depress respiration, although at high doses it actually increases it.
Proenkephalin (PENK), formerly known as proenkephalin A, is an endogenous opioid polypeptide hormone which, via proteolyic cleavage, produces the enkephalin peptides [Met]enkephalin, and to a lesser extent, [Leu]enkephalin. Upon cleavage, each proenkephalin peptide results in the generation of four copies of [Met]enkephalin, two extended copies of [Met]enkephalin, and one copy of [Leu]enkephalin. Contrarily, [Leu]enkephalin] is predominantly synthesized from prodynorphin, which produces three copies of it per cleavage, and no copies of [Met]enkephalin. Other endogenous opioid peptides produced by proenkephalin include adrenorphin, amidorphin, BAM-18, BAM-20P, BAM-22P, peptide B, peptide E, and peptide F.
Metkefamide (INN; LY-127,623), or metkephamid acetate (USAN), but most frequently referred to simply as metkephamid, is a synthetic opioid pentapeptide and derivative of [Met]enkephalin with the amino acid sequence Tyr-D-Ala-Gly-Phe-(N-Me)-Met-NH2. It behaves as a potent agonist of the δ- and μ-opioid receptors with roughly equipotent affinity, and also has similarly high affinity as well as subtype-selectivity for the κ3-opioid receptor.
Pain in cephalopods is a contentious issue. Pain is a complex mental state, with a distinct perceptual quality but also associated with suffering, which is an emotional state. Because of this complexity, the presence of pain in non-human animals, or another human for that matter, cannot be determined unambiguously using observational methods, but the conclusion that animals experience pain is often inferred on the basis of likely presence of phenomenal consciousness which is deduced from comparative brain physiology as well as physical and behavioural reactions.
