Stress, Anxiety, and Immunomodulation: A Pharmacological Analysis.

Stress and stressful events are common occurrences in our daily lives and such aversive situations bring about complex changes in the biological system. Such stress responses influence the brain and behavior, neuroendocrine and immune systems, and these responses orchestrate to increase or decrease the ability of the organism to cope with such stressors. The brain via expression of complex behavioral paradigms controls peripheral responses to stress and a bidirectional link exists in the modulation of stress effects. Anxiety is a common neurobehavioral correlate of a variety of stressors, and both acute and chronic stress exposure could precipitate anxiety disorders. Psychoneuroimmunology involves interactions between the brain and the immune system, and it is now being increasingly recognized that the immune system could contribute to the neurobehavioral responses to stress. Studies have shown that the brain and its complex neurotransmitter networks could influence immune function, and there could be a possible link between anxiogenesis and immunomodulation during stress. Physiological and pharmacological data have highlighted this concept, and the present review gives an overview of the relationship between stress, anxiety, and immune responsiveness.

Differential effects of intrahypothalamic administration of opioids on food intake in naive and tolerant rats.

We investigated the effects of intrahypothalamic administrations of the opioid agonists morphine (MOR) and ketocyclazocine (KCZ) and antagonists naltrexone (NALTX) and Mr2266 on food intake (FI) during light and dark phases of the diurnal cycle, after acute or chronic administration in rats. Acute intralateral hypothalamic (LH) administration of MOR or KCZ (1 microgram/rat) enhanced FI during dark and light phases, respectively, whereas intraventromedial hypothalamic (VMH) injections resulted in moderate hyperphagia during dark phases by both mu and kappa agonists. The receptor specificity was evident from blockade of the responses to MOR or KCZ by the respective antagonists NALTX and Mr2266. After repeated administrations of MOR and KCZ, FI responses to the test dose of these agonists injected in LH were modulated in opposite directions. However, the adaptative changes in FI after intra-VMH injection of KCZ were similar to those seen with MOR. These results are discussed in light of a differential opioid receptor involvement and their possible functional interactions within the hypothalamus during food intake.

Pharmacological studies on 2-(2-(4-(3-methylphenyl)-1-piperazinyl)ethyl) quinoline (centhaquin). I. Hypotensive activity.

Hypotensive activity of 2-(2-(4-(3-methylphenyl)-1-piperazinyl)ethyl) quinoline (compound 71/73; centhaquin) was studied in cat and rat. The compound lowered the blood pressure and reduced the heart rate of anaesthetized and unanaesthetized (decerebrate) cat in a dose-dependent manner (0.01-1.0 mg/kg i.v. or 1.0-2.5 mg/kg intraduodenally). The hypotensive effect was insignificant in spinal transected cat but more marked in deafferented and vagotomized animals. Localization of centhaquin to brain by intravertebral arterial injection (5-10 micrograms) or by topical application to the exposed ventral surface of medulla or floor of the fourth ventricle caused hypotension and bradycardia as well as reduced the excitability of the vasomotor loci. It was also effective in rats after single as well as multiple dosing. The compound seems to act centrally to reduce the blood pressure.

On the mechanisms of hypotensive action of indoramin.

Effect of indoramin in small doses on the central vasomotor loci has been studied in chloralose anesthetized cats by localizing it to the central sites. An intracerebroventricular dose of 100 micrograms or intra-vertebral arterial injection of 50 micrograms significantly inhibited the excitability of hypothalamic and medullary vasomotor loci and produced hypotension. Similarly, topical application of indoramin (0.5%) to the floor of the IV ventricle inhibited the medullary and the hypothalamic vasomotor responses but a similar application to the ventral surface of the medulla had no effect. An intrathecal dose of 100 micrograms did not inhibit the spinal compression vasmotor response. Administration of higher amounts led to inhibition of the adrenaline pressor response also, indicating a peripheral leak of the drug. Indoramin has a definite inhibitory effect on the medullary vasomotor loci which contributes to the hypotension produced by this drug.