Pituitary-adrenal axis and oral morphine consumption in rats.

Removal of the pituitary gland in rats leads to suppression of oral morphine and quinine intake behavior. Experiments measuring oral intake of solutions containing graded concentrations of morphine or quinine, revealed that the detection acuity for bitter taste is changed in hypophysectomized (hypox) animals. Treatment of these rats with ACTH 1--24 restored oral morphine intake towards that on intact rats.

Adrenocorticotrophic hormone fragments mimic the effect of morphine in vitro.

1 Fragments of the N terminal part of adrenocorticotrophic hormone (ACTH) inhibited the electrically evoked contractions of the mouse vas deferens. This inhibition could be antagonized by naloxone. 2 The same fragments displaced radiolabelled morphine from morphine antiserum.

Modification of conditioned behavior of rats by neurohypophyseal hormones and analogues.

Vasopressin and other neurohypophyseal peptides affect various processes related to memory and/or learning. A single subcutaneous injection of vasopressin increases resistance to extinction of a pole-jumping avoidance response in rat. This test system has been applied in an attempt to relate structural aspects of neurohypophyseal peptides, analogues, and derivatives with truncated sequences to their effects on conditioned behavior.

ACTH-induced lipolysis in rat adipocytes: structure-activity relationships.

The lipolytic action of natural porcine ACTH1(-39) and of a number of highly purified synthetic ACTH peptide fragments was studied using rat adipocytes. Of the analogues tested, only ACTH1(-24) exhibited full lipolytic activity with respect to intrinsic activity and affinity. Several shorter fragments appeared to be full agonists but had lower affinity.

Intravenous self-administration of drugs in rats.

A standardized self-administration procedure in rats was used to determine the intravenous self-administration liability of graded doses of various drugs. Self-administration was reliably established with the tested addictive drugs (morphine, heroin, fentanyl and d-amphetamine), but not with the nonaddictive drugs (chlorpromazine and nalorphine). However, 1 out of 14 animals on nalorphine clearly demonstrated self-administering behavior.

Behavioral and electrophysiological effects of peptides related to lipotropin (beta-LPH).

Both C-terminal fragments of lipotropin (beta-LPH) (endorphins) and N-terminal fragments (e.g., ACTH 4-10) delayed extinction of pole-jumping avoidance behavior in rats.

Narcotic cueing properties of intraventricularly administered sufentanil, fentanyl, morphine and met-enkephalin.

The narcotic cueing activity of sufentanil, fentanyl, morphine and met-enkephalin was studied upon their injection into the lateral brain ventricle of the rat. Comparative studies on the analgesic activity of the three narcotics support a close correlation between the narcotic cueing and the analgesic activity of narcotic drugs.

Modulation of heroin self-administration by neurohypophyseal principles.

Neuropeptides related to hypothalomic-neurohypophyseal hormones affect intravenous heroin self-administration behavior in rats. Desglycinamide9, arginine8-vasopressin and pressinamide reduced, while oxytocin and its C-terminal tripeptide, prolyl-leucyl-glycinamide facilitated this behavior. The effectiveness of the vasopressin analogue appeared to be of a long term nature.

Differential localization of pituitary-adrenal activation and temperature changes following intrahypothalamic microinjection of morphine in rats.

Microinjections of morphine (MOR) into the basal mid-hypothalamus of rats elevate corticosteroid production of adrenal glands in vitro and plasma corticosterone (B) levels. Injections in or close to the rostral part of the arcuate nucleus were most effective in producing pituitary-adrenal activation, without affecting body temperature. Injections of MOR in the anterior hypothalamic area caused hyperthermia or hypothermia, depending on the dose and the site of injection, with little or no effect on piutitary-adrenal activity.

Correlation between hypothalamic catecholamine synthesis and ether stress-induced ACTH secretion.

The rates of synthesis of norepinephrine (NE) and dopamine (DA) in several regions of the hypothalamus have been estimated after exposure of rats to stresses that increase ACTH secretion. The rate of 3H-NE and 3H-DA accumulation from 3H-tyrosine in vitro was used as an index of catecholamine synthesis rates. Exposure to ether vapor, 30 min of cold environment, or laparotomy increased ACTH secretion significantly, as indicated by plasma corticosterone levels.