Serotonin-regulated thermal

One important neuronal TRH control center appears to be the paraventricular nucleus, but TRH Is widely distributed in the hypothalamus and highly concentrated in the median eminence (4). One important ipactor regulating TRH production is environmental temperature. Both peripheral thermal receptors and preoptic neuronal thermal receptors monitor environmental and central body temperature these receptors modulate preoptic neuronal outflow to the paraventricular nucleus and other TRH synthesizing neurons in the hypothalamus and median eminence which. In turn, modulate TRH secretion (4). Decreasing environmental and/or core body temperature Increase TRH output and increase the tonic level of TSH release. Somatostatin (SRIF) and dopamine can inhibit TSH release by actions at the pituitary level, and these inhibitory transmitters contribute to central nervous system modulation of TSH release (4). There is evidence that serotonin may be inhibitory in the adult rat, but this does not seem to be so in other species. Norepinephrine also may be inhibitory. Glucocorticoid can inhibit TSH release at the hypothalamic level, but the mechanism is not known. The exact roles of TRH and non-TRH regulatory factors in TSH control are not clear. Administration of somatostatin antiserum to adult rats increases basal TSH levels and potentiates the TSH response to cold (19). Inhibitory factors probably also play a role in the diurnal variation in TSH secretion, in the inhibitory reactions to stress, in the variation in thyroidal activity in psychosis, etc. 

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