EXPERIMENT I
On 13 February 2001, 60 adult standard dark female mink were assigned
at random to one of ten groups (Table). Mink in groups 1-8 were subjected
to a photoperiod for Southeast Idaho, animals in groups 9 and 10 were exposed
to an artificially long photoperiod of 16L: 8D (Rose and Sterner,
1992)Animals in groups 2 and 3 each received a single Silastic implant,
containing 150 mg of deoxycorticosterone (DOC), to maintain fluid and electrolyte
balance following ADX. On 2/16, animals in group 3 were ADX’d under
isoflourane anesthesia (Rose 1995). Animals in groups 7 and 8 each
received two sc haloperidol (HAL, 200mg, 60 day release) implants, to increase
PRL secretion. Mink in groups 4, 8 and 10 each received a single
Silastic sc implant containing 25 mg melatonin (MEL). Mink in groups
5 and 6 each received a single commercial implant containing either 8 mg
(group 5) or 5 mg (group 6) of MEL.
ADX’d mink appear to exhibit little or no telogen
phase following surgery (Rose et al., 1998, Johnston and Rose, 1999). We
therefore, attempted to determine if a period of zero hair growth occurs
after ADX, which would indicate telogen. To accomplish this, ADX’d mink
were re-sheared each time the maximal hair length was observed (5/22 and
7/24) and measurements of guard hair length taken at weekly intervals until
9/11.
Finally, to determine the long-term effects of
MEL on initiation of winter anagen, and skin PRL-R levels, we retained
a small number of mink (control, N=2, MEL 8mg, N=5, and MEL 5 mg, N=2)
until 9/29. In addition ADX, (N=3) and DOC-treated mink (N=2) were
also retained to determine their effects on skin PRL-R levels. Fur growth
measurements were continually made on these animals until 9/29, when they
were sacrificed. Skin samples were then analyzed for PRL-R levels (Rose,
1995) and serum for PRL concentrations (Rose et al., 1998).
EXPERIMENT II
An experiment was conducted in which mink were made hyperprolactinemic
(HAL), and hypoprolactinemic (MEL) to determine the effects of PRL on:
1. depilation-induced anagen, 2. under hair follicle density, and 3. skin
PRL-R concentrations. On 2/ 20, 12 additional adult female mink were assigned
to one of three treatment groups. Mink in group one represented controls,
receiving no further treatment. Mink in group two each received a single
HAL implant sc, and mink in group three each received a single MEL implant
(8 mg) as described above. Blood samples were collected by jugular
venapuncture on 2/20, 3/4, 3/23, 4/1, 4/25 and 5/6 and assayed for serum
PRL levels (Rose et al., 1998). Between 3/4 and 3/5 all mink were
depilated to induce anagen. Hair growth was subsequently measured as described
above. After the guard hairs had attained a length of 5mm or more (ensuring
that the under hair follicular bundles would have formed), the animals
were sacrificed for collection of skin and blood samples. Serum was assayed
for PRL concentrations and skin for under hair follicle density as described
above.
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