Effects of catecholamine synthesis inhibitors and adrenergic receptor antagonists on restraint-induced LH release

Acute stress is known to increase LH secretion and the release of central norepinephrine (NE) in intact rats. Studies were performed to analyse the ole of catecholamines in acute stress-induced LH release in male rats. Injection of alpha-methyl-p-tyrosine (alpha MPT) and diethyldithiocarbamate (DDC), catecholamine synthesis inhibitors, significantly decreased both hypothalamic concentration of NE and serum LH. Restraint for 30 min evoked an increase in serum LH in saline-treated rats, whereas alpha MPT and DDC administration blocked the stress-induced LH release. The effects of alpha 1-, alpha 2- and beta-adrenoreceptor antagonists on the LH response to restraint stress were also studied. Propranolol treatment did not modify serum LH in either unstressed or stressed rats. The two alpha-adrenergic receptor antagonists prazosin and yohimbine prevented the restraint-induced LH release; however, prazosin but not yohimbine significantly decreased the serum concentration of LH in unstressed rats. These data suggest that the acute stress-induced increase in LH secretion is mediated through the activation of alpha 2-adrenergic receptors.