Opiates physiological effects

Agonist drugs can also bind directly to the postsynaptic receptor, so mimicking the physiological effect of the neurotransmitter for example, morphine and heroin bind to the brain s opiate receptors and, thus, directly stimulate feelings of pleasure and pain... 

Medical Use of Opiate Drugs Acute Psychological and Physiological Effects of Opiates Chronic Effects of Opiates Tolerance... 

Because ACTH synthesis originates from the POMC precursor peptide, its production by the pituitary is closely tied to the secretion of endogenous opiate peptides, such as P-endorphin. The physiological effects of endogenous opiates include (1) sedation, (2) an increased threshold of pain, and (3) autonomic regulation of respiration, blood pressure, and heart rate. These peptides are also involved in modifying endocrine responses to stress and water balance... 

Met-enkephalin and leu-enkephalin belong to a group of peptides called the opioid peptides, found predominantly in nerve tissue cells. Opioid peptides are molecules that relieve pain (a protective mechanism in animals that warns of tissue damage) and produce pleasant sensations. They were discovered after researchers suspected that the physiological effects of opiate drugs such as morphine resulted from their binding to nerve cell receptors for endogenous molecules. Leu-enkephalin and met-enkephalin are pentapeptides that differ only in their C-terminal amino acid residues. Substance P and bradykinin stimulate the perception of pain, an effect opposed by the opioid peptides. 

What physiologic effects are manifested with opiate-induced depression of medullary respiratory centers ... 

No. Tolerance is not seen with chronic administration, and withdrawal of the drug does not precipitate adverse physiologic effects in non-opiate-dependent persons. 

Basic drugs elicit a variety of physiological effects. Stimulants such as methamphetamine can act as haUudnogens at higher doses, while the opiate alkaloids are analgesic and promote general depression of the central nervous system. Many natural products, such as cocoa leaves, peyote, and khat leaves, have been used for hundreds of years. Some— for example, LSD and mescaline— are associated with religious explorations or celebrations. 

P-Endorphin. A peptide corresponding to the 31 C-terminal amino acids of P-LPH was first discovered in camel pituitary tissue (10). This substance is P-endorphin, which exerts a potent analgesic effect by binding to cell surface receptors in the central nervous system. The sequence of P-endorphin is well conserved across species for the first 25 N-terminal amino acids. Opiates derived from plant sources, eg, heroin, morphine, opium, etc, exert their actions by interacting with the P-endorphin receptor. On a molar basis, this peptide has approximately five times the potency of morphine. Both P-endorphin and ACTH ate cosecreted from the pituitary gland. Whereas the physiologic importance of P-endorphin release into the systemic circulation is not certain, this molecule clearly has been shown to be an important neurotransmitter within the central nervous system. Endorphin has been invaluable as a research tool, but has not been clinically useful due to the avadabihty of plant-derived opiates. 

Acute physiological responses to opiate administration occur rapidly and include constricted pupils, decreased pulse rate, reduced body temperature, slowed respiration rate and impaired reflexes. In addition, there is a marked slowing of the digestive system through an altering of the tonus and motility of the stomach and intestines, allowing for greater water absorption. This last effect is not subject to tolerance, and constipation is a common side effect even for chronic users. Indeed, some report that this is the worst side effect of opiate use. 

Only one antagonist is known, naloxone, which is used clinically to treat opiate overdoses and, experimentally, to investigate whether physiological or biochemical actions are opiate-mediated. One example of its use is to support the hypothesis that P-endorphin is responsible for the analgesic effects of acupuncture. Not only does low frequency electroacupuncture increase p-endorphin levels in cerebrospinal fluid but naloxone nullifies the analgesic effect of this treatment. 

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