And another thing (Re: MSH)

[From Bruce Abbott (951008.1430 EST)]

After you push that little "send" button, you can't stop the message from
going out. I forgot to add a title to my last post (951008.1230 EST) and
overlooked a couple of other points as well.

First, I want correct something: MSH stands for "melanocyte" (not
"melatonin") stimulating hormone. I don't know where my brain came up with
melatonin; if it doesn't exist is certainly ought to! Second, I wanted to
respond to this:

Bill Powers (951008.0815 MDT) --

What MSH should have done
for these chicks was to make them appear tanned under their feathers --
did anyone look? Or, according to some recent studies, MSH should have
enabled these chicks to sleep better at night (that's why you can now
buy melatonin pills at health food stores). I don't know of any studies
with humans of the kind you describe, but apparently MSH ought to have
an effect on human distress vocalizations under at least some
conditions. Do you really expect that this would happen?

Allow me to quote from the introduction to the paper:

    Several neuropeptides modulate emotional processes when administered
    centrally. The most extensively studied emotional effect has been the
    ability of various opiod peptides to inhibit separation distress in
    domestic chicks. All opiod peptides that can activate mu receptors are
    highly effective in reducing distress vocalizations (DVs) arising from
    social separation. In contrast, corticotrophin releasing factor (CRF)
    can increase various behavioral indices that suggest elevated
    emotional distress. In domestic chicks, CRF appears to directly trigger
    the neuronal machinery of distress vocalization. the peptide can
    produce high levels of DVs even in animals tested in the presence of
    social stimuli that normally quiet the animals, such as mirrored
    environments, sound, or the presence of the flock. The fact that
    endorphin- and CRF-containing neuronal systems of the brain overlap
    extensively with distress vocalization circuitry suggests that the two
    peptides normally exert neurophysiological control over distress
    vocalization circuitry in the brain.

    A system that exhibits similar neuroanatomical trajectories to those of
    endorphin and CRF is alpha-melanocyte stimulating hormone (alpha-MSH). MSH
    and beta-endorphine arise from the same pro-opiomelanocortin (POMC)
    peptide precursor and are colocalized in neurons of the basal ventro-
    medial hypothalamus, although more recent immunocytochemical work also
    indicates the existence of MSH-like peptide systems having a much wider
    hypothalamic distribution. Accordingly, it might be anticipated that
    alpha-MSH would also affect distress vocalizations.
        (Panksepp and Abbott, 1990, p. 647)

Although we usually think of alpha-MSH as stimulating the production of skin
pigmentation, most (if not all) hormones found in other parts of the body
have also been found to have receptor sites in the brain, where the roles
they play may differ from those of the periphery. MSH does not cross the
blood-brain barrier, so there would be no reason to expect that MSH secreted
in target neuron terminals would have any effect on skin coloration. The
fact that MSH and beta-endorphin are created by cleaving the same precursor
molecule means that the same factors that stimulate the production of
beta-endorphin would also stimulate production of alpha-MSH as a byproduct
and vice versa. This chemical relationship could have provided the
conditions through which alpha-MSH levels became associated over the course
of evolution with brain processes related to those in which beta-endorphin
participates.

If anyone is interested in reading this paper the reference is:

Panksepp, J., & Abbott, B. B. (1990). Modulation of separation distress
    by alpha-MSH. _Peptides_, _11_, 647-653.

Regards,

Bruce