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The term Lewis reaction is used too, named after Thomas Lewis, who first described the effect in 1930. [1] Vasoconstriction occurs first to reduce heat loss, but also results in strong cooling of the extremities. Approximately five to ten minutes after the start of cold exposure, the blood vessels in the extremities will suddenly vasodilate.
The test can detect antipsychotic-like activity both in the case of dopamine D 2 receptor antagonists and in the case of drugs lacking D 2 receptor antagonism. [1] [2] [6] The occupancy of the D 2 receptor by antagonists of this receptor required to inhibit the CAR is around 65 to 80%, which is similar to the occupancy at which therapeutic antipsychotic effects occur in humans with these drugs.
Other signals associated with hunger also affect the HPT axis. Insulin and bile acids, which are elevated after a meal, lead to increased D2 activity, [2] therefore increasing T3 and reducing rT3. Low leptin increases NPY and AGRP (associated with appetite), which inhibit TRH gene expression; this effect is enhanced by ghrelin (the hunger hormone).
The first stage of cold water immersion syndrome, the cold shock response, includes a group of reflexes lasting under 5 min in laboratory volunteers and initiated by thermoreceptors sensing rapid skin cooling. Water has a thermal conductivity 25 times and a volume-specific heat capacity over 3000 times that of air; subsequently, surface cooling ...
Ambient temperature is an example of exogenous vasoconstriction. Cutaneous vasoconstriction will occur because of the body's exposure to the severe cold. Examples of endogenous factors include the autonomic nervous system, circulating hormones, and intrinsic mechanisms inherent to the vasculature itself (also referred to as the myogenic response).
These effects are the result of activation of 5-HT 1A receptors within the rostral ventrolateral medulla. [10] The sympatholytic antihypertensive drug urapidil is an α 1-adrenergic receptor antagonist and 5-HT 1A receptor agonist, and it has been demonstrated that the latter property contributes to its overall therapeutic effects.
l-DOPA is produced from the amino acid l-tyrosine by the enzyme tyrosine hydroxylase. l-DOPA can act as an l-tyrosine mimetic and be incorporated into proteins by mammalian cells in place of l-tyrosine, generating protease-resistant and aggregate-prone proteins in vitro and may contribute to neurotoxicity with chronic l-DOPA administration. [10]
The dose–response relationship, or exposure–response relationship, describes the magnitude of the response of an organism, as a function of exposure (or doses) to a stimulus or stressor (usually a chemical) after a certain exposure time. [1] Dose–response relationships can be described by dose–response curves. This is explained further ...